6122f3e60d
branch. This brings us very close to the 3.0 release, which is expected in a week or two. MFC after: 1 week
1990 lines
72 KiB
C++
1990 lines
72 KiB
C++
//===- RegisterCoalescer.cpp - Generic Register Coalescing Interface -------==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the generic RegisterCoalescer interface which
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// is used as the common interface used by all clients and
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// implementations of register coalescing.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "regcoalescing"
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#include "RegisterCoalescer.h"
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#include "LiveDebugVariables.h"
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#include "RegisterClassInfo.h"
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#include "VirtRegMap.h"
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#include "llvm/Pass.h"
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#include "llvm/Value.h"
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#include "llvm/CodeGen/LiveIntervalAnalysis.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/CodeGen/LiveIntervalAnalysis.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetOptions.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/OwningPtr.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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#include <algorithm>
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#include <cmath>
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using namespace llvm;
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STATISTIC(numJoins , "Number of interval joins performed");
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STATISTIC(numCrossRCs , "Number of cross class joins performed");
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STATISTIC(numCommutes , "Number of instruction commuting performed");
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STATISTIC(numExtends , "Number of copies extended");
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STATISTIC(NumReMats , "Number of instructions re-materialized");
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STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
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STATISTIC(numAborts , "Number of times interval joining aborted");
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STATISTIC(NumInflated , "Number of register classes inflated");
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static cl::opt<bool>
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EnableJoining("join-liveintervals",
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cl::desc("Coalesce copies (default=true)"),
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cl::init(true));
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static cl::opt<bool>
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DisableCrossClassJoin("disable-cross-class-join",
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cl::desc("Avoid coalescing cross register class copies"),
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cl::init(false), cl::Hidden);
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static cl::opt<bool>
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EnablePhysicalJoin("join-physregs",
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cl::desc("Join physical register copies"),
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cl::init(false), cl::Hidden);
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static cl::opt<bool>
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VerifyCoalescing("verify-coalescing",
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cl::desc("Verify machine instrs before and after register coalescing"),
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cl::Hidden);
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namespace {
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class RegisterCoalescer : public MachineFunctionPass {
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MachineFunction* MF;
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MachineRegisterInfo* MRI;
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const TargetMachine* TM;
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const TargetRegisterInfo* TRI;
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const TargetInstrInfo* TII;
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LiveIntervals *LIS;
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LiveDebugVariables *LDV;
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const MachineLoopInfo* Loops;
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AliasAnalysis *AA;
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RegisterClassInfo RegClassInfo;
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/// JoinedCopies - Keep track of copies eliminated due to coalescing.
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///
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SmallPtrSet<MachineInstr*, 32> JoinedCopies;
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/// ReMatCopies - Keep track of copies eliminated due to remat.
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///
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SmallPtrSet<MachineInstr*, 32> ReMatCopies;
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/// ReMatDefs - Keep track of definition instructions which have
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/// been remat'ed.
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SmallPtrSet<MachineInstr*, 8> ReMatDefs;
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/// joinIntervals - join compatible live intervals
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void joinIntervals();
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/// CopyCoalesceInMBB - Coalesce copies in the specified MBB, putting
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/// copies that cannot yet be coalesced into the "TryAgain" list.
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void CopyCoalesceInMBB(MachineBasicBlock *MBB,
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std::vector<MachineInstr*> &TryAgain);
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/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
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/// which are the src/dst of the copy instruction CopyMI. This returns
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/// true if the copy was successfully coalesced away. If it is not
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/// currently possible to coalesce this interval, but it may be possible if
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/// other things get coalesced, then it returns true by reference in
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/// 'Again'.
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bool JoinCopy(MachineInstr *TheCopy, bool &Again);
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/// JoinIntervals - Attempt to join these two intervals. On failure, this
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/// returns false. The output "SrcInt" will not have been modified, so we
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/// can use this information below to update aliases.
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bool JoinIntervals(CoalescerPair &CP);
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/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
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/// the source value number is defined by a copy from the destination reg
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/// see if we can merge these two destination reg valno# into a single
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/// value number, eliminating a copy.
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bool AdjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
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/// HasOtherReachingDefs - Return true if there are definitions of IntB
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/// other than BValNo val# that can reach uses of AValno val# of IntA.
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bool HasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
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VNInfo *AValNo, VNInfo *BValNo);
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/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy.
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/// If the source value number is defined by a commutable instruction and
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/// its other operand is coalesced to the copy dest register, see if we
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/// can transform the copy into a noop by commuting the definition.
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bool RemoveCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
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/// ReMaterializeTrivialDef - If the source of a copy is defined by a
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/// trivial computation, replace the copy by rematerialize the definition.
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/// If PreserveSrcInt is true, make sure SrcInt is valid after the call.
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bool ReMaterializeTrivialDef(LiveInterval &SrcInt, bool PreserveSrcInt,
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unsigned DstReg, MachineInstr *CopyMI);
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/// shouldJoinPhys - Return true if a physreg copy should be joined.
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bool shouldJoinPhys(CoalescerPair &CP);
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/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
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/// two virtual registers from different register classes.
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bool isWinToJoinCrossClass(unsigned SrcReg,
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unsigned DstReg,
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const TargetRegisterClass *SrcRC,
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const TargetRegisterClass *DstRC,
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const TargetRegisterClass *NewRC);
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/// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
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/// update the subregister number if it is not zero. If DstReg is a
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/// physical register and the existing subregister number of the def / use
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/// being updated is not zero, make sure to set it to the correct physical
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/// subregister.
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void UpdateRegDefsUses(const CoalescerPair &CP);
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/// RemoveDeadDef - If a def of a live interval is now determined dead,
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/// remove the val# it defines. If the live interval becomes empty, remove
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/// it as well.
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bool RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
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/// RemoveCopyFlag - If DstReg is no longer defined by CopyMI, clear the
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/// VNInfo copy flag for DstReg and all aliases.
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void RemoveCopyFlag(unsigned DstReg, const MachineInstr *CopyMI);
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/// markAsJoined - Remember that CopyMI has already been joined.
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void markAsJoined(MachineInstr *CopyMI);
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/// eliminateUndefCopy - Handle copies of undef values.
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bool eliminateUndefCopy(MachineInstr *CopyMI, const CoalescerPair &CP);
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public:
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static char ID; // Class identification, replacement for typeinfo
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RegisterCoalescer() : MachineFunctionPass(ID) {
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initializeRegisterCoalescerPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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virtual void releaseMemory();
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/// runOnMachineFunction - pass entry point
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virtual bool runOnMachineFunction(MachineFunction&);
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/// print - Implement the dump method.
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virtual void print(raw_ostream &O, const Module* = 0) const;
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};
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} /// end anonymous namespace
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char &llvm::RegisterCoalescerPassID = RegisterCoalescer::ID;
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INITIALIZE_PASS_BEGIN(RegisterCoalescer, "simple-register-coalescing",
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"Simple Register Coalescing", false, false)
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INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
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INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
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INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
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INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
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INITIALIZE_PASS_DEPENDENCY(StrongPHIElimination)
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INITIALIZE_PASS_DEPENDENCY(PHIElimination)
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INITIALIZE_PASS_DEPENDENCY(TwoAddressInstructionPass)
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INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
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INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing",
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"Simple Register Coalescing", false, false)
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char RegisterCoalescer::ID = 0;
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static unsigned compose(const TargetRegisterInfo &tri, unsigned a, unsigned b) {
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if (!a) return b;
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if (!b) return a;
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return tri.composeSubRegIndices(a, b);
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}
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static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI,
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unsigned &Src, unsigned &Dst,
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unsigned &SrcSub, unsigned &DstSub) {
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if (MI->isCopy()) {
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Dst = MI->getOperand(0).getReg();
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DstSub = MI->getOperand(0).getSubReg();
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Src = MI->getOperand(1).getReg();
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SrcSub = MI->getOperand(1).getSubReg();
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} else if (MI->isSubregToReg()) {
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Dst = MI->getOperand(0).getReg();
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DstSub = compose(tri, MI->getOperand(0).getSubReg(),
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MI->getOperand(3).getImm());
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Src = MI->getOperand(2).getReg();
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SrcSub = MI->getOperand(2).getSubReg();
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} else
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return false;
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return true;
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}
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bool CoalescerPair::setRegisters(const MachineInstr *MI) {
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SrcReg = DstReg = SubIdx = 0;
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NewRC = 0;
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Flipped = CrossClass = false;
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unsigned Src, Dst, SrcSub, DstSub;
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if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
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return false;
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Partial = SrcSub || DstSub;
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// If one register is a physreg, it must be Dst.
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if (TargetRegisterInfo::isPhysicalRegister(Src)) {
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if (TargetRegisterInfo::isPhysicalRegister(Dst))
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return false;
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std::swap(Src, Dst);
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std::swap(SrcSub, DstSub);
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Flipped = true;
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}
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const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
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if (TargetRegisterInfo::isPhysicalRegister(Dst)) {
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// Eliminate DstSub on a physreg.
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if (DstSub) {
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Dst = TRI.getSubReg(Dst, DstSub);
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if (!Dst) return false;
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DstSub = 0;
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}
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// Eliminate SrcSub by picking a corresponding Dst superregister.
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if (SrcSub) {
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Dst = TRI.getMatchingSuperReg(Dst, SrcSub, MRI.getRegClass(Src));
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if (!Dst) return false;
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SrcSub = 0;
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} else if (!MRI.getRegClass(Src)->contains(Dst)) {
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return false;
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}
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} else {
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// Both registers are virtual.
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// Both registers have subreg indices.
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if (SrcSub && DstSub) {
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// For now we only handle the case of identical indices in commensurate
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// registers: Dreg:ssub_1 + Dreg:ssub_1 -> Dreg
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// FIXME: Handle Qreg:ssub_3 + Dreg:ssub_1 as QReg:dsub_1 + Dreg.
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if (SrcSub != DstSub)
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return false;
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const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
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const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
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if (!TRI.getCommonSubClass(DstRC, SrcRC))
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return false;
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SrcSub = DstSub = 0;
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}
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// There can be no SrcSub.
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if (SrcSub) {
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std::swap(Src, Dst);
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DstSub = SrcSub;
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SrcSub = 0;
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assert(!Flipped && "Unexpected flip");
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Flipped = true;
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}
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// Find the new register class.
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const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
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const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
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if (DstSub)
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NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
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else
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NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
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if (!NewRC)
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return false;
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CrossClass = NewRC != DstRC || NewRC != SrcRC;
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}
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// Check our invariants
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assert(TargetRegisterInfo::isVirtualRegister(Src) && "Src must be virtual");
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assert(!(TargetRegisterInfo::isPhysicalRegister(Dst) && DstSub) &&
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"Cannot have a physical SubIdx");
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SrcReg = Src;
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DstReg = Dst;
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SubIdx = DstSub;
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return true;
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}
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bool CoalescerPair::flip() {
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if (SubIdx || TargetRegisterInfo::isPhysicalRegister(DstReg))
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return false;
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std::swap(SrcReg, DstReg);
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Flipped = !Flipped;
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return true;
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}
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bool CoalescerPair::isCoalescable(const MachineInstr *MI) const {
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if (!MI)
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return false;
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unsigned Src, Dst, SrcSub, DstSub;
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if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
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return false;
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// Find the virtual register that is SrcReg.
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if (Dst == SrcReg) {
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std::swap(Src, Dst);
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std::swap(SrcSub, DstSub);
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} else if (Src != SrcReg) {
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return false;
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}
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// Now check that Dst matches DstReg.
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if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
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if (!TargetRegisterInfo::isPhysicalRegister(Dst))
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return false;
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assert(!SubIdx && "Inconsistent CoalescerPair state.");
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// DstSub could be set for a physreg from INSERT_SUBREG.
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if (DstSub)
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Dst = TRI.getSubReg(Dst, DstSub);
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// Full copy of Src.
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if (!SrcSub)
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return DstReg == Dst;
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// This is a partial register copy. Check that the parts match.
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return TRI.getSubReg(DstReg, SrcSub) == Dst;
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} else {
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// DstReg is virtual.
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if (DstReg != Dst)
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return false;
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// Registers match, do the subregisters line up?
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return compose(TRI, SubIdx, SrcSub) == DstSub;
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}
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}
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void RegisterCoalescer::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addRequired<AliasAnalysis>();
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AU.addRequired<LiveIntervals>();
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AU.addPreserved<LiveIntervals>();
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AU.addRequired<LiveDebugVariables>();
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AU.addPreserved<LiveDebugVariables>();
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AU.addPreserved<SlotIndexes>();
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AU.addRequired<MachineLoopInfo>();
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AU.addPreserved<MachineLoopInfo>();
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AU.addPreservedID(MachineDominatorsID);
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AU.addPreservedID(StrongPHIEliminationID);
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AU.addPreservedID(PHIEliminationID);
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AU.addPreservedID(TwoAddressInstructionPassID);
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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void RegisterCoalescer::markAsJoined(MachineInstr *CopyMI) {
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/// Joined copies are not deleted immediately, but kept in JoinedCopies.
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JoinedCopies.insert(CopyMI);
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/// Mark all register operands of CopyMI as <undef> so they won't affect dead
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/// code elimination.
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for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
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E = CopyMI->operands_end(); I != E; ++I)
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if (I->isReg())
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I->setIsUndef(true);
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}
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/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA
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/// being the source and IntB being the dest, thus this defines a value number
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/// in IntB. If the source value number (in IntA) is defined by a copy from B,
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/// see if we can merge these two pieces of B into a single value number,
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/// eliminating a copy. For example:
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///
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/// A3 = B0
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/// ...
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/// B1 = A3 <- this copy
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///
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/// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
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/// value number to be replaced with B0 (which simplifies the B liveinterval).
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///
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/// This returns true if an interval was modified.
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///
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bool RegisterCoalescer::AdjustCopiesBackFrom(const CoalescerPair &CP,
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MachineInstr *CopyMI) {
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// Bail if there is no dst interval - can happen when merging physical subreg
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// operations.
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if (!LIS->hasInterval(CP.getDstReg()))
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return false;
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LiveInterval &IntA =
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LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
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LiveInterval &IntB =
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LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
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SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
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// BValNo is a value number in B that is defined by a copy from A. 'B3' in
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// the example above.
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LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
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if (BLR == IntB.end()) return false;
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VNInfo *BValNo = BLR->valno;
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// Get the location that B is defined at. Two options: either this value has
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// an unknown definition point or it is defined at CopyIdx. If unknown, we
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// can't process it.
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if (!BValNo->isDefByCopy()) return false;
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assert(BValNo->def == CopyIdx && "Copy doesn't define the value?");
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// AValNo is the value number in A that defines the copy, A3 in the example.
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SlotIndex CopyUseIdx = CopyIdx.getUseIndex();
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LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx);
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// The live range might not exist after fun with physreg coalescing.
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if (ALR == IntA.end()) return false;
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VNInfo *AValNo = ALR->valno;
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// If it's re-defined by an early clobber somewhere in the live range, then
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// it's not safe to eliminate the copy. FIXME: This is a temporary workaround.
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// See PR3149:
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// 172 %ECX<def> = MOV32rr %reg1039<kill>
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// 180 INLINEASM <es:subl $5,$1
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// sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9,
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// %EAX<kill>,
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// 36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0
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// 188 %EAX<def> = MOV32rr %EAX<kill>
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// 196 %ECX<def> = MOV32rr %ECX<kill>
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// 204 %ECX<def> = MOV32rr %ECX<kill>
|
|
// 212 %EAX<def> = MOV32rr %EAX<kill>
|
|
// 220 %EAX<def> = MOV32rr %EAX
|
|
// 228 %reg1039<def> = MOV32rr %ECX<kill>
|
|
// The early clobber operand ties ECX input to the ECX def.
|
|
//
|
|
// The live interval of ECX is represented as this:
|
|
// %reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47)
|
|
// The coalescer has no idea there was a def in the middle of [174,230].
|
|
if (AValNo->hasRedefByEC())
|
|
return false;
|
|
|
|
// If AValNo is defined as a copy from IntB, we can potentially process this.
|
|
// Get the instruction that defines this value number.
|
|
if (!CP.isCoalescable(AValNo->getCopy()))
|
|
return false;
|
|
|
|
// Get the LiveRange in IntB that this value number starts with.
|
|
LiveInterval::iterator ValLR =
|
|
IntB.FindLiveRangeContaining(AValNo->def.getPrevSlot());
|
|
if (ValLR == IntB.end())
|
|
return false;
|
|
|
|
// Make sure that the end of the live range is inside the same block as
|
|
// CopyMI.
|
|
MachineInstr *ValLREndInst =
|
|
LIS->getInstructionFromIndex(ValLR->end.getPrevSlot());
|
|
if (!ValLREndInst || ValLREndInst->getParent() != CopyMI->getParent())
|
|
return false;
|
|
|
|
// Okay, we now know that ValLR ends in the same block that the CopyMI
|
|
// live-range starts. If there are no intervening live ranges between them in
|
|
// IntB, we can merge them.
|
|
if (ValLR+1 != BLR) return false;
|
|
|
|
// If a live interval is a physical register, conservatively check if any
|
|
// of its aliases is overlapping the live interval of the virtual register.
|
|
// If so, do not coalesce.
|
|
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
|
|
for (const unsigned *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
|
|
if (LIS->hasInterval(*AS) && IntA.overlaps(LIS->getInterval(*AS))) {
|
|
DEBUG({
|
|
dbgs() << "\t\tInterfere with alias ";
|
|
LIS->getInterval(*AS).print(dbgs(), TRI);
|
|
});
|
|
return false;
|
|
}
|
|
}
|
|
|
|
DEBUG({
|
|
dbgs() << "Extending: ";
|
|
IntB.print(dbgs(), TRI);
|
|
});
|
|
|
|
SlotIndex FillerStart = ValLR->end, FillerEnd = BLR->start;
|
|
// We are about to delete CopyMI, so need to remove it as the 'instruction
|
|
// that defines this value #'. Update the valnum with the new defining
|
|
// instruction #.
|
|
BValNo->def = FillerStart;
|
|
BValNo->setCopy(0);
|
|
|
|
// Okay, we can merge them. We need to insert a new liverange:
|
|
// [ValLR.end, BLR.begin) of either value number, then we merge the
|
|
// two value numbers.
|
|
IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
|
|
|
|
// If the IntB live range is assigned to a physical register, and if that
|
|
// physreg has sub-registers, update their live intervals as well.
|
|
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
|
|
for (const unsigned *SR = TRI->getSubRegisters(IntB.reg); *SR; ++SR) {
|
|
if (!LIS->hasInterval(*SR))
|
|
continue;
|
|
LiveInterval &SRLI = LIS->getInterval(*SR);
|
|
SRLI.addRange(LiveRange(FillerStart, FillerEnd,
|
|
SRLI.getNextValue(FillerStart, 0,
|
|
LIS->getVNInfoAllocator())));
|
|
}
|
|
}
|
|
|
|
// Okay, merge "B1" into the same value number as "B0".
|
|
if (BValNo != ValLR->valno) {
|
|
// If B1 is killed by a PHI, then the merged live range must also be killed
|
|
// by the same PHI, as B0 and B1 can not overlap.
|
|
bool HasPHIKill = BValNo->hasPHIKill();
|
|
IntB.MergeValueNumberInto(BValNo, ValLR->valno);
|
|
if (HasPHIKill)
|
|
ValLR->valno->setHasPHIKill(true);
|
|
}
|
|
DEBUG({
|
|
dbgs() << " result = ";
|
|
IntB.print(dbgs(), TRI);
|
|
dbgs() << "\n";
|
|
});
|
|
|
|
// If the source instruction was killing the source register before the
|
|
// merge, unset the isKill marker given the live range has been extended.
|
|
int UIdx = ValLREndInst->findRegisterUseOperandIdx(IntB.reg, true);
|
|
if (UIdx != -1) {
|
|
ValLREndInst->getOperand(UIdx).setIsKill(false);
|
|
}
|
|
|
|
// If the copy instruction was killing the destination register before the
|
|
// merge, find the last use and trim the live range. That will also add the
|
|
// isKill marker.
|
|
if (ALR->end == CopyIdx)
|
|
LIS->shrinkToUses(&IntA);
|
|
|
|
++numExtends;
|
|
return true;
|
|
}
|
|
|
|
/// HasOtherReachingDefs - Return true if there are definitions of IntB
|
|
/// other than BValNo val# that can reach uses of AValno val# of IntA.
|
|
bool RegisterCoalescer::HasOtherReachingDefs(LiveInterval &IntA,
|
|
LiveInterval &IntB,
|
|
VNInfo *AValNo,
|
|
VNInfo *BValNo) {
|
|
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
|
|
AI != AE; ++AI) {
|
|
if (AI->valno != AValNo) continue;
|
|
LiveInterval::Ranges::iterator BI =
|
|
std::upper_bound(IntB.ranges.begin(), IntB.ranges.end(), AI->start);
|
|
if (BI != IntB.ranges.begin())
|
|
--BI;
|
|
for (; BI != IntB.ranges.end() && AI->end >= BI->start; ++BI) {
|
|
if (BI->valno == BValNo)
|
|
continue;
|
|
if (BI->start <= AI->start && BI->end > AI->start)
|
|
return true;
|
|
if (BI->start > AI->start && BI->start < AI->end)
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy with
|
|
/// IntA being the source and IntB being the dest, thus this defines a value
|
|
/// number in IntB. If the source value number (in IntA) is defined by a
|
|
/// commutable instruction and its other operand is coalesced to the copy dest
|
|
/// register, see if we can transform the copy into a noop by commuting the
|
|
/// definition. For example,
|
|
///
|
|
/// A3 = op A2 B0<kill>
|
|
/// ...
|
|
/// B1 = A3 <- this copy
|
|
/// ...
|
|
/// = op A3 <- more uses
|
|
///
|
|
/// ==>
|
|
///
|
|
/// B2 = op B0 A2<kill>
|
|
/// ...
|
|
/// B1 = B2 <- now an identify copy
|
|
/// ...
|
|
/// = op B2 <- more uses
|
|
///
|
|
/// This returns true if an interval was modified.
|
|
///
|
|
bool RegisterCoalescer::RemoveCopyByCommutingDef(const CoalescerPair &CP,
|
|
MachineInstr *CopyMI) {
|
|
// FIXME: For now, only eliminate the copy by commuting its def when the
|
|
// source register is a virtual register. We want to guard against cases
|
|
// where the copy is a back edge copy and commuting the def lengthen the
|
|
// live interval of the source register to the entire loop.
|
|
if (CP.isPhys() && CP.isFlipped())
|
|
return false;
|
|
|
|
// Bail if there is no dst interval.
|
|
if (!LIS->hasInterval(CP.getDstReg()))
|
|
return false;
|
|
|
|
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
|
|
|
|
LiveInterval &IntA =
|
|
LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
|
|
LiveInterval &IntB =
|
|
LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
|
|
|
|
// BValNo is a value number in B that is defined by a copy from A. 'B3' in
|
|
// the example above.
|
|
VNInfo *BValNo = IntB.getVNInfoAt(CopyIdx);
|
|
if (!BValNo || !BValNo->isDefByCopy())
|
|
return false;
|
|
|
|
assert(BValNo->def == CopyIdx && "Copy doesn't define the value?");
|
|
|
|
// AValNo is the value number in A that defines the copy, A3 in the example.
|
|
VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getUseIndex());
|
|
assert(AValNo && "COPY source not live");
|
|
|
|
// If other defs can reach uses of this def, then it's not safe to perform
|
|
// the optimization.
|
|
if (AValNo->isPHIDef() || AValNo->isUnused() || AValNo->hasPHIKill())
|
|
return false;
|
|
MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
|
|
if (!DefMI)
|
|
return false;
|
|
const MCInstrDesc &MCID = DefMI->getDesc();
|
|
if (!MCID.isCommutable())
|
|
return false;
|
|
// If DefMI is a two-address instruction then commuting it will change the
|
|
// destination register.
|
|
int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
|
|
assert(DefIdx != -1);
|
|
unsigned UseOpIdx;
|
|
if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
|
|
return false;
|
|
unsigned Op1, Op2, NewDstIdx;
|
|
if (!TII->findCommutedOpIndices(DefMI, Op1, Op2))
|
|
return false;
|
|
if (Op1 == UseOpIdx)
|
|
NewDstIdx = Op2;
|
|
else if (Op2 == UseOpIdx)
|
|
NewDstIdx = Op1;
|
|
else
|
|
return false;
|
|
|
|
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
|
|
unsigned NewReg = NewDstMO.getReg();
|
|
if (NewReg != IntB.reg || !NewDstMO.isKill())
|
|
return false;
|
|
|
|
// Make sure there are no other definitions of IntB that would reach the
|
|
// uses which the new definition can reach.
|
|
if (HasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
|
|
return false;
|
|
|
|
// Abort if the aliases of IntB.reg have values that are not simply the
|
|
// clobbers from the superreg.
|
|
if (TargetRegisterInfo::isPhysicalRegister(IntB.reg))
|
|
for (const unsigned *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
|
|
if (LIS->hasInterval(*AS) &&
|
|
HasOtherReachingDefs(IntA, LIS->getInterval(*AS), AValNo, 0))
|
|
return false;
|
|
|
|
// If some of the uses of IntA.reg is already coalesced away, return false.
|
|
// It's not possible to determine whether it's safe to perform the coalescing.
|
|
for (MachineRegisterInfo::use_nodbg_iterator UI =
|
|
MRI->use_nodbg_begin(IntA.reg),
|
|
UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
|
|
MachineInstr *UseMI = &*UI;
|
|
SlotIndex UseIdx = LIS->getInstructionIndex(UseMI);
|
|
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
|
|
if (ULR == IntA.end())
|
|
continue;
|
|
if (ULR->valno == AValNo && JoinedCopies.count(UseMI))
|
|
return false;
|
|
}
|
|
|
|
DEBUG(dbgs() << "\tRemoveCopyByCommutingDef: " << AValNo->def << '\t'
|
|
<< *DefMI);
|
|
|
|
// At this point we have decided that it is legal to do this
|
|
// transformation. Start by commuting the instruction.
|
|
MachineBasicBlock *MBB = DefMI->getParent();
|
|
MachineInstr *NewMI = TII->commuteInstruction(DefMI);
|
|
if (!NewMI)
|
|
return false;
|
|
if (TargetRegisterInfo::isVirtualRegister(IntA.reg) &&
|
|
TargetRegisterInfo::isVirtualRegister(IntB.reg) &&
|
|
!MRI->constrainRegClass(IntB.reg, MRI->getRegClass(IntA.reg)))
|
|
return false;
|
|
if (NewMI != DefMI) {
|
|
LIS->ReplaceMachineInstrInMaps(DefMI, NewMI);
|
|
MBB->insert(DefMI, NewMI);
|
|
MBB->erase(DefMI);
|
|
}
|
|
unsigned OpIdx = NewMI->findRegisterUseOperandIdx(IntA.reg, false);
|
|
NewMI->getOperand(OpIdx).setIsKill();
|
|
|
|
// If ALR and BLR overlaps and end of BLR extends beyond end of ALR, e.g.
|
|
// A = or A, B
|
|
// ...
|
|
// B = A
|
|
// ...
|
|
// C = A<kill>
|
|
// ...
|
|
// = B
|
|
|
|
// Update uses of IntA of the specific Val# with IntB.
|
|
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(IntA.reg),
|
|
UE = MRI->use_end(); UI != UE;) {
|
|
MachineOperand &UseMO = UI.getOperand();
|
|
MachineInstr *UseMI = &*UI;
|
|
++UI;
|
|
if (JoinedCopies.count(UseMI))
|
|
continue;
|
|
if (UseMI->isDebugValue()) {
|
|
// FIXME These don't have an instruction index. Not clear we have enough
|
|
// info to decide whether to do this replacement or not. For now do it.
|
|
UseMO.setReg(NewReg);
|
|
continue;
|
|
}
|
|
SlotIndex UseIdx = LIS->getInstructionIndex(UseMI).getUseIndex();
|
|
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
|
|
if (ULR == IntA.end() || ULR->valno != AValNo)
|
|
continue;
|
|
if (TargetRegisterInfo::isPhysicalRegister(NewReg))
|
|
UseMO.substPhysReg(NewReg, *TRI);
|
|
else
|
|
UseMO.setReg(NewReg);
|
|
if (UseMI == CopyMI)
|
|
continue;
|
|
if (!UseMI->isCopy())
|
|
continue;
|
|
if (UseMI->getOperand(0).getReg() != IntB.reg ||
|
|
UseMI->getOperand(0).getSubReg())
|
|
continue;
|
|
|
|
// This copy will become a noop. If it's defining a new val#, merge it into
|
|
// BValNo.
|
|
SlotIndex DefIdx = UseIdx.getDefIndex();
|
|
VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
|
|
if (!DVNI)
|
|
continue;
|
|
DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
|
|
assert(DVNI->def == DefIdx);
|
|
BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
|
|
markAsJoined(UseMI);
|
|
}
|
|
|
|
// Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
|
|
// is updated.
|
|
VNInfo *ValNo = BValNo;
|
|
ValNo->def = AValNo->def;
|
|
ValNo->setCopy(0);
|
|
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
|
|
AI != AE; ++AI) {
|
|
if (AI->valno != AValNo) continue;
|
|
IntB.addRange(LiveRange(AI->start, AI->end, ValNo));
|
|
}
|
|
DEBUG(dbgs() << "\t\textended: " << IntB << '\n');
|
|
|
|
IntA.removeValNo(AValNo);
|
|
DEBUG(dbgs() << "\t\ttrimmed: " << IntA << '\n');
|
|
++numCommutes;
|
|
return true;
|
|
}
|
|
|
|
/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
|
|
/// computation, replace the copy by rematerialize the definition.
|
|
bool RegisterCoalescer::ReMaterializeTrivialDef(LiveInterval &SrcInt,
|
|
bool preserveSrcInt,
|
|
unsigned DstReg,
|
|
MachineInstr *CopyMI) {
|
|
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getUseIndex();
|
|
LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
|
|
assert(SrcLR != SrcInt.end() && "Live range not found!");
|
|
VNInfo *ValNo = SrcLR->valno;
|
|
if (ValNo->isPHIDef() || ValNo->isUnused())
|
|
return false;
|
|
MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
|
|
if (!DefMI)
|
|
return false;
|
|
assert(DefMI && "Defining instruction disappeared");
|
|
const MCInstrDesc &MCID = DefMI->getDesc();
|
|
if (!MCID.isAsCheapAsAMove())
|
|
return false;
|
|
if (!TII->isTriviallyReMaterializable(DefMI, AA))
|
|
return false;
|
|
bool SawStore = false;
|
|
if (!DefMI->isSafeToMove(TII, AA, SawStore))
|
|
return false;
|
|
if (MCID.getNumDefs() != 1)
|
|
return false;
|
|
if (!DefMI->isImplicitDef()) {
|
|
// Make sure the copy destination register class fits the instruction
|
|
// definition register class. The mismatch can happen as a result of earlier
|
|
// extract_subreg, insert_subreg, subreg_to_reg coalescing.
|
|
const TargetRegisterClass *RC = TII->getRegClass(MCID, 0, TRI);
|
|
if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
|
|
if (MRI->getRegClass(DstReg) != RC)
|
|
return false;
|
|
} else if (!RC->contains(DstReg))
|
|
return false;
|
|
}
|
|
|
|
RemoveCopyFlag(DstReg, CopyMI);
|
|
|
|
MachineBasicBlock *MBB = CopyMI->getParent();
|
|
MachineBasicBlock::iterator MII =
|
|
llvm::next(MachineBasicBlock::iterator(CopyMI));
|
|
TII->reMaterialize(*MBB, MII, DstReg, 0, DefMI, *TRI);
|
|
MachineInstr *NewMI = prior(MII);
|
|
|
|
// CopyMI may have implicit operands, transfer them over to the newly
|
|
// rematerialized instruction. And update implicit def interval valnos.
|
|
for (unsigned i = CopyMI->getDesc().getNumOperands(),
|
|
e = CopyMI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = CopyMI->getOperand(i);
|
|
if (MO.isReg() && MO.isImplicit())
|
|
NewMI->addOperand(MO);
|
|
if (MO.isDef())
|
|
RemoveCopyFlag(MO.getReg(), CopyMI);
|
|
}
|
|
|
|
NewMI->copyImplicitOps(CopyMI);
|
|
LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
|
|
CopyMI->eraseFromParent();
|
|
ReMatCopies.insert(CopyMI);
|
|
ReMatDefs.insert(DefMI);
|
|
DEBUG(dbgs() << "Remat: " << *NewMI);
|
|
++NumReMats;
|
|
|
|
// The source interval can become smaller because we removed a use.
|
|
if (preserveSrcInt)
|
|
LIS->shrinkToUses(&SrcInt);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// eliminateUndefCopy - ProcessImpicitDefs may leave some copies of <undef>
|
|
/// values, it only removes local variables. When we have a copy like:
|
|
///
|
|
/// %vreg1 = COPY %vreg2<undef>
|
|
///
|
|
/// We delete the copy and remove the corresponding value number from %vreg1.
|
|
/// Any uses of that value number are marked as <undef>.
|
|
bool RegisterCoalescer::eliminateUndefCopy(MachineInstr *CopyMI,
|
|
const CoalescerPair &CP) {
|
|
SlotIndex Idx = LIS->getInstructionIndex(CopyMI);
|
|
LiveInterval *SrcInt = &LIS->getInterval(CP.getSrcReg());
|
|
if (SrcInt->liveAt(Idx))
|
|
return false;
|
|
LiveInterval *DstInt = &LIS->getInterval(CP.getDstReg());
|
|
if (DstInt->liveAt(Idx))
|
|
return false;
|
|
|
|
// No intervals are live-in to CopyMI - it is undef.
|
|
if (CP.isFlipped())
|
|
DstInt = SrcInt;
|
|
SrcInt = 0;
|
|
|
|
VNInfo *DeadVNI = DstInt->getVNInfoAt(Idx.getDefIndex());
|
|
assert(DeadVNI && "No value defined in DstInt");
|
|
DstInt->removeValNo(DeadVNI);
|
|
|
|
// Find new undef uses.
|
|
for (MachineRegisterInfo::reg_nodbg_iterator
|
|
I = MRI->reg_nodbg_begin(DstInt->reg), E = MRI->reg_nodbg_end();
|
|
I != E; ++I) {
|
|
MachineOperand &MO = I.getOperand();
|
|
if (MO.isDef() || MO.isUndef())
|
|
continue;
|
|
MachineInstr *MI = MO.getParent();
|
|
SlotIndex Idx = LIS->getInstructionIndex(MI);
|
|
if (DstInt->liveAt(Idx))
|
|
continue;
|
|
MO.setIsUndef(true);
|
|
DEBUG(dbgs() << "\tnew undef: " << Idx << '\t' << *MI);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
|
|
/// update the subregister number if it is not zero. If DstReg is a
|
|
/// physical register and the existing subregister number of the def / use
|
|
/// being updated is not zero, make sure to set it to the correct physical
|
|
/// subregister.
|
|
void
|
|
RegisterCoalescer::UpdateRegDefsUses(const CoalescerPair &CP) {
|
|
bool DstIsPhys = CP.isPhys();
|
|
unsigned SrcReg = CP.getSrcReg();
|
|
unsigned DstReg = CP.getDstReg();
|
|
unsigned SubIdx = CP.getSubIdx();
|
|
|
|
// Update LiveDebugVariables.
|
|
LDV->renameRegister(SrcReg, DstReg, SubIdx);
|
|
|
|
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
|
|
MachineInstr *UseMI = I.skipInstruction();) {
|
|
// A PhysReg copy that won't be coalesced can perhaps be rematerialized
|
|
// instead.
|
|
if (DstIsPhys) {
|
|
if (UseMI->isFullCopy() &&
|
|
UseMI->getOperand(1).getReg() == SrcReg &&
|
|
UseMI->getOperand(0).getReg() != SrcReg &&
|
|
UseMI->getOperand(0).getReg() != DstReg &&
|
|
!JoinedCopies.count(UseMI) &&
|
|
ReMaterializeTrivialDef(LIS->getInterval(SrcReg), false,
|
|
UseMI->getOperand(0).getReg(), UseMI))
|
|
continue;
|
|
}
|
|
|
|
SmallVector<unsigned,8> Ops;
|
|
bool Reads, Writes;
|
|
tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
|
|
bool Kills = false, Deads = false;
|
|
|
|
// Replace SrcReg with DstReg in all UseMI operands.
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
MachineOperand &MO = UseMI->getOperand(Ops[i]);
|
|
Kills |= MO.isKill();
|
|
Deads |= MO.isDead();
|
|
|
|
// Make sure we don't create read-modify-write defs accidentally. We
|
|
// assume here that a SrcReg def cannot be joined into a live DstReg. If
|
|
// RegisterCoalescer starts tracking partially live registers, we will
|
|
// need to check the actual LiveInterval to determine if DstReg is live
|
|
// here.
|
|
if (SubIdx && !Reads)
|
|
MO.setIsUndef();
|
|
|
|
if (DstIsPhys)
|
|
MO.substPhysReg(DstReg, *TRI);
|
|
else
|
|
MO.substVirtReg(DstReg, SubIdx, *TRI);
|
|
}
|
|
|
|
// This instruction is a copy that will be removed.
|
|
if (JoinedCopies.count(UseMI))
|
|
continue;
|
|
|
|
if (SubIdx) {
|
|
// If UseMI was a simple SrcReg def, make sure we didn't turn it into a
|
|
// read-modify-write of DstReg.
|
|
if (Deads)
|
|
UseMI->addRegisterDead(DstReg, TRI);
|
|
else if (!Reads && Writes)
|
|
UseMI->addRegisterDefined(DstReg, TRI);
|
|
|
|
// Kill flags apply to the whole physical register.
|
|
if (DstIsPhys && Kills)
|
|
UseMI->addRegisterKilled(DstReg, TRI);
|
|
}
|
|
|
|
DEBUG({
|
|
dbgs() << "\t\tupdated: ";
|
|
if (!UseMI->isDebugValue())
|
|
dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
|
|
dbgs() << *UseMI;
|
|
});
|
|
}
|
|
}
|
|
|
|
/// removeIntervalIfEmpty - Check if the live interval of a physical register
|
|
/// is empty, if so remove it and also remove the empty intervals of its
|
|
/// sub-registers. Return true if live interval is removed.
|
|
static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *LIS,
|
|
const TargetRegisterInfo *TRI) {
|
|
if (li.empty()) {
|
|
if (TargetRegisterInfo::isPhysicalRegister(li.reg))
|
|
for (const unsigned* SR = TRI->getSubRegisters(li.reg); *SR; ++SR) {
|
|
if (!LIS->hasInterval(*SR))
|
|
continue;
|
|
LiveInterval &sli = LIS->getInterval(*SR);
|
|
if (sli.empty())
|
|
LIS->removeInterval(*SR);
|
|
}
|
|
LIS->removeInterval(li.reg);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// RemoveDeadDef - If a def of a live interval is now determined dead, remove
|
|
/// the val# it defines. If the live interval becomes empty, remove it as well.
|
|
bool RegisterCoalescer::RemoveDeadDef(LiveInterval &li,
|
|
MachineInstr *DefMI) {
|
|
SlotIndex DefIdx = LIS->getInstructionIndex(DefMI).getDefIndex();
|
|
LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
|
|
if (DefIdx != MLR->valno->def)
|
|
return false;
|
|
li.removeValNo(MLR->valno);
|
|
return removeIntervalIfEmpty(li, LIS, TRI);
|
|
}
|
|
|
|
void RegisterCoalescer::RemoveCopyFlag(unsigned DstReg,
|
|
const MachineInstr *CopyMI) {
|
|
SlotIndex DefIdx = LIS->getInstructionIndex(CopyMI).getDefIndex();
|
|
if (LIS->hasInterval(DstReg)) {
|
|
LiveInterval &LI = LIS->getInterval(DstReg);
|
|
if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx))
|
|
if (LR->valno->def == DefIdx)
|
|
LR->valno->setCopy(0);
|
|
}
|
|
if (!TargetRegisterInfo::isPhysicalRegister(DstReg))
|
|
return;
|
|
for (const unsigned* AS = TRI->getAliasSet(DstReg); *AS; ++AS) {
|
|
if (!LIS->hasInterval(*AS))
|
|
continue;
|
|
LiveInterval &LI = LIS->getInterval(*AS);
|
|
if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx))
|
|
if (LR->valno->def == DefIdx)
|
|
LR->valno->setCopy(0);
|
|
}
|
|
}
|
|
|
|
/// shouldJoinPhys - Return true if a copy involving a physreg should be joined.
|
|
/// We need to be careful about coalescing a source physical register with a
|
|
/// virtual register. Once the coalescing is done, it cannot be broken and these
|
|
/// are not spillable! If the destination interval uses are far away, think
|
|
/// twice about coalescing them!
|
|
bool RegisterCoalescer::shouldJoinPhys(CoalescerPair &CP) {
|
|
bool Allocatable = LIS->isAllocatable(CP.getDstReg());
|
|
LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
|
|
|
|
/// Always join simple intervals that are defined by a single copy from a
|
|
/// reserved register. This doesn't increase register pressure, so it is
|
|
/// always beneficial.
|
|
if (!Allocatable && CP.isFlipped() && JoinVInt.containsOneValue())
|
|
return true;
|
|
|
|
if (!EnablePhysicalJoin) {
|
|
DEBUG(dbgs() << "\tPhysreg joins disabled.\n");
|
|
return false;
|
|
}
|
|
|
|
// Only coalesce to allocatable physreg, we don't want to risk modifying
|
|
// reserved registers.
|
|
if (!Allocatable) {
|
|
DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n");
|
|
return false; // Not coalescable.
|
|
}
|
|
|
|
// Don't join with physregs that have a ridiculous number of live
|
|
// ranges. The data structure performance is really bad when that
|
|
// happens.
|
|
if (LIS->hasInterval(CP.getDstReg()) &&
|
|
LIS->getInterval(CP.getDstReg()).ranges.size() > 1000) {
|
|
++numAborts;
|
|
DEBUG(dbgs()
|
|
<< "\tPhysical register live interval too complicated, abort!\n");
|
|
return false;
|
|
}
|
|
|
|
// FIXME: Why are we skipping this test for partial copies?
|
|
// CodeGen/X86/phys_subreg_coalesce-3.ll needs it.
|
|
if (!CP.isPartial()) {
|
|
const TargetRegisterClass *RC = MRI->getRegClass(CP.getSrcReg());
|
|
unsigned Threshold = RegClassInfo.getNumAllocatableRegs(RC) * 2;
|
|
unsigned Length = LIS->getApproximateInstructionCount(JoinVInt);
|
|
if (Length > Threshold) {
|
|
++numAborts;
|
|
DEBUG(dbgs() << "\tMay tie down a physical register, abort!\n");
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
|
|
/// two virtual registers from different register classes.
|
|
bool
|
|
RegisterCoalescer::isWinToJoinCrossClass(unsigned SrcReg,
|
|
unsigned DstReg,
|
|
const TargetRegisterClass *SrcRC,
|
|
const TargetRegisterClass *DstRC,
|
|
const TargetRegisterClass *NewRC) {
|
|
unsigned NewRCCount = RegClassInfo.getNumAllocatableRegs(NewRC);
|
|
// This heuristics is good enough in practice, but it's obviously not *right*.
|
|
// 4 is a magic number that works well enough for x86, ARM, etc. It filter
|
|
// out all but the most restrictive register classes.
|
|
if (NewRCCount > 4 ||
|
|
// Early exit if the function is fairly small, coalesce aggressively if
|
|
// that's the case. For really special register classes with 3 or
|
|
// fewer registers, be a bit more careful.
|
|
(LIS->getFuncInstructionCount() / NewRCCount) < 8)
|
|
return true;
|
|
LiveInterval &SrcInt = LIS->getInterval(SrcReg);
|
|
LiveInterval &DstInt = LIS->getInterval(DstReg);
|
|
unsigned SrcSize = LIS->getApproximateInstructionCount(SrcInt);
|
|
unsigned DstSize = LIS->getApproximateInstructionCount(DstInt);
|
|
|
|
// Coalesce aggressively if the intervals are small compared to the number of
|
|
// registers in the new class. The number 4 is fairly arbitrary, chosen to be
|
|
// less aggressive than the 8 used for the whole function size.
|
|
const unsigned ThresSize = 4 * NewRCCount;
|
|
if (SrcSize <= ThresSize && DstSize <= ThresSize)
|
|
return true;
|
|
|
|
// Estimate *register use density*. If it doubles or more, abort.
|
|
unsigned SrcUses = std::distance(MRI->use_nodbg_begin(SrcReg),
|
|
MRI->use_nodbg_end());
|
|
unsigned DstUses = std::distance(MRI->use_nodbg_begin(DstReg),
|
|
MRI->use_nodbg_end());
|
|
unsigned NewUses = SrcUses + DstUses;
|
|
unsigned NewSize = SrcSize + DstSize;
|
|
if (SrcRC != NewRC && SrcSize > ThresSize) {
|
|
unsigned SrcRCCount = RegClassInfo.getNumAllocatableRegs(SrcRC);
|
|
if (NewUses*SrcSize*SrcRCCount > 2*SrcUses*NewSize*NewRCCount)
|
|
return false;
|
|
}
|
|
if (DstRC != NewRC && DstSize > ThresSize) {
|
|
unsigned DstRCCount = RegClassInfo.getNumAllocatableRegs(DstRC);
|
|
if (NewUses*DstSize*DstRCCount > 2*DstUses*NewSize*NewRCCount)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
|
|
/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
|
|
/// which are the src/dst of the copy instruction CopyMI. This returns true
|
|
/// if the copy was successfully coalesced away. If it is not currently
|
|
/// possible to coalesce this interval, but it may be possible if other
|
|
/// things get coalesced, then it returns true by reference in 'Again'.
|
|
bool RegisterCoalescer::JoinCopy(MachineInstr *CopyMI, bool &Again) {
|
|
|
|
Again = false;
|
|
if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
|
|
return false; // Already done.
|
|
|
|
DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
|
|
|
|
CoalescerPair CP(*TII, *TRI);
|
|
if (!CP.setRegisters(CopyMI)) {
|
|
DEBUG(dbgs() << "\tNot coalescable.\n");
|
|
return false;
|
|
}
|
|
|
|
// If they are already joined we continue.
|
|
if (CP.getSrcReg() == CP.getDstReg()) {
|
|
markAsJoined(CopyMI);
|
|
DEBUG(dbgs() << "\tCopy already coalesced.\n");
|
|
return false; // Not coalescable.
|
|
}
|
|
|
|
// Eliminate undefs.
|
|
if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
|
|
markAsJoined(CopyMI);
|
|
DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
|
|
return false; // Not coalescable.
|
|
}
|
|
|
|
DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
|
|
<< " with " << PrintReg(CP.getDstReg(), TRI, CP.getSubIdx())
|
|
<< "\n");
|
|
|
|
// Enforce policies.
|
|
if (CP.isPhys()) {
|
|
if (!shouldJoinPhys(CP)) {
|
|
// Before giving up coalescing, if definition of source is defined by
|
|
// trivial computation, try rematerializing it.
|
|
if (!CP.isFlipped() &&
|
|
ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
|
|
CP.getDstReg(), CopyMI))
|
|
return true;
|
|
return false;
|
|
}
|
|
} else {
|
|
// Avoid constraining virtual register regclass too much.
|
|
if (CP.isCrossClass()) {
|
|
DEBUG(dbgs() << "\tCross-class to " << CP.getNewRC()->getName() << ".\n");
|
|
if (DisableCrossClassJoin) {
|
|
DEBUG(dbgs() << "\tCross-class joins disabled.\n");
|
|
return false;
|
|
}
|
|
if (!isWinToJoinCrossClass(CP.getSrcReg(), CP.getDstReg(),
|
|
MRI->getRegClass(CP.getSrcReg()),
|
|
MRI->getRegClass(CP.getDstReg()),
|
|
CP.getNewRC())) {
|
|
DEBUG(dbgs() << "\tAvoid coalescing to constrained register class.\n");
|
|
Again = true; // May be possible to coalesce later.
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// When possible, let DstReg be the larger interval.
|
|
if (!CP.getSubIdx() && LIS->getInterval(CP.getSrcReg()).ranges.size() >
|
|
LIS->getInterval(CP.getDstReg()).ranges.size())
|
|
CP.flip();
|
|
}
|
|
|
|
// Okay, attempt to join these two intervals. On failure, this returns false.
|
|
// Otherwise, if one of the intervals being joined is a physreg, this method
|
|
// always canonicalizes DstInt to be it. The output "SrcInt" will not have
|
|
// been modified, so we can use this information below to update aliases.
|
|
if (!JoinIntervals(CP)) {
|
|
// Coalescing failed.
|
|
|
|
// If definition of source is defined by trivial computation, try
|
|
// rematerializing it.
|
|
if (!CP.isFlipped() &&
|
|
ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
|
|
CP.getDstReg(), CopyMI))
|
|
return true;
|
|
|
|
// If we can eliminate the copy without merging the live ranges, do so now.
|
|
if (!CP.isPartial()) {
|
|
if (AdjustCopiesBackFrom(CP, CopyMI) ||
|
|
RemoveCopyByCommutingDef(CP, CopyMI)) {
|
|
markAsJoined(CopyMI);
|
|
DEBUG(dbgs() << "\tTrivial!\n");
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Otherwise, we are unable to join the intervals.
|
|
DEBUG(dbgs() << "\tInterference!\n");
|
|
Again = true; // May be possible to coalesce later.
|
|
return false;
|
|
}
|
|
|
|
// Coalescing to a virtual register that is of a sub-register class of the
|
|
// other. Make sure the resulting register is set to the right register class.
|
|
if (CP.isCrossClass()) {
|
|
++numCrossRCs;
|
|
MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
|
|
}
|
|
|
|
// Remember to delete the copy instruction.
|
|
markAsJoined(CopyMI);
|
|
|
|
UpdateRegDefsUses(CP);
|
|
|
|
// If we have extended the live range of a physical register, make sure we
|
|
// update live-in lists as well.
|
|
if (CP.isPhys()) {
|
|
SmallVector<MachineBasicBlock*, 16> BlockSeq;
|
|
// JoinIntervals invalidates the VNInfos in SrcInt, but we only need the
|
|
// ranges for this, and they are preserved.
|
|
LiveInterval &SrcInt = LIS->getInterval(CP.getSrcReg());
|
|
for (LiveInterval::const_iterator I = SrcInt.begin(), E = SrcInt.end();
|
|
I != E; ++I ) {
|
|
LIS->findLiveInMBBs(I->start, I->end, BlockSeq);
|
|
for (unsigned idx = 0, size = BlockSeq.size(); idx != size; ++idx) {
|
|
MachineBasicBlock &block = *BlockSeq[idx];
|
|
if (!block.isLiveIn(CP.getDstReg()))
|
|
block.addLiveIn(CP.getDstReg());
|
|
}
|
|
BlockSeq.clear();
|
|
}
|
|
}
|
|
|
|
// SrcReg is guarateed to be the register whose live interval that is
|
|
// being merged.
|
|
LIS->removeInterval(CP.getSrcReg());
|
|
|
|
// Update regalloc hint.
|
|
TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
|
|
|
|
DEBUG({
|
|
LiveInterval &DstInt = LIS->getInterval(CP.getDstReg());
|
|
dbgs() << "\tJoined. Result = ";
|
|
DstInt.print(dbgs(), TRI);
|
|
dbgs() << "\n";
|
|
});
|
|
|
|
++numJoins;
|
|
return true;
|
|
}
|
|
|
|
/// ComputeUltimateVN - Assuming we are going to join two live intervals,
|
|
/// compute what the resultant value numbers for each value in the input two
|
|
/// ranges will be. This is complicated by copies between the two which can
|
|
/// and will commonly cause multiple value numbers to be merged into one.
|
|
///
|
|
/// VN is the value number that we're trying to resolve. InstDefiningValue
|
|
/// keeps track of the new InstDefiningValue assignment for the result
|
|
/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
|
|
/// whether a value in this or other is a copy from the opposite set.
|
|
/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
|
|
/// already been assigned.
|
|
///
|
|
/// ThisFromOther[x] - If x is defined as a copy from the other interval, this
|
|
/// contains the value number the copy is from.
|
|
///
|
|
static unsigned ComputeUltimateVN(VNInfo *VNI,
|
|
SmallVector<VNInfo*, 16> &NewVNInfo,
|
|
DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
|
|
DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
|
|
SmallVector<int, 16> &ThisValNoAssignments,
|
|
SmallVector<int, 16> &OtherValNoAssignments) {
|
|
unsigned VN = VNI->id;
|
|
|
|
// If the VN has already been computed, just return it.
|
|
if (ThisValNoAssignments[VN] >= 0)
|
|
return ThisValNoAssignments[VN];
|
|
assert(ThisValNoAssignments[VN] != -2 && "Cyclic value numbers");
|
|
|
|
// If this val is not a copy from the other val, then it must be a new value
|
|
// number in the destination.
|
|
DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
|
|
if (I == ThisFromOther.end()) {
|
|
NewVNInfo.push_back(VNI);
|
|
return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
|
|
}
|
|
VNInfo *OtherValNo = I->second;
|
|
|
|
// Otherwise, this *is* a copy from the RHS. If the other side has already
|
|
// been computed, return it.
|
|
if (OtherValNoAssignments[OtherValNo->id] >= 0)
|
|
return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
|
|
|
|
// Mark this value number as currently being computed, then ask what the
|
|
// ultimate value # of the other value is.
|
|
ThisValNoAssignments[VN] = -2;
|
|
unsigned UltimateVN =
|
|
ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
|
|
OtherValNoAssignments, ThisValNoAssignments);
|
|
return ThisValNoAssignments[VN] = UltimateVN;
|
|
}
|
|
|
|
|
|
// Find out if we have something like
|
|
// A = X
|
|
// B = X
|
|
// if so, we can pretend this is actually
|
|
// A = X
|
|
// B = A
|
|
// which allows us to coalesce A and B.
|
|
// VNI is the definition of B. LR is the life range of A that includes
|
|
// the slot just before B. If we return true, we add "B = X" to DupCopies.
|
|
// This implies that A dominates B.
|
|
static bool RegistersDefinedFromSameValue(LiveIntervals &li,
|
|
const TargetRegisterInfo &tri,
|
|
CoalescerPair &CP,
|
|
VNInfo *VNI,
|
|
LiveRange *LR,
|
|
SmallVector<MachineInstr*, 8> &DupCopies) {
|
|
// FIXME: This is very conservative. For example, we don't handle
|
|
// physical registers.
|
|
|
|
MachineInstr *MI = VNI->getCopy();
|
|
|
|
if (!MI->isFullCopy() || CP.isPartial() || CP.isPhys())
|
|
return false;
|
|
|
|
unsigned Dst = MI->getOperand(0).getReg();
|
|
unsigned Src = MI->getOperand(1).getReg();
|
|
|
|
if (!TargetRegisterInfo::isVirtualRegister(Src) ||
|
|
!TargetRegisterInfo::isVirtualRegister(Dst))
|
|
return false;
|
|
|
|
unsigned A = CP.getDstReg();
|
|
unsigned B = CP.getSrcReg();
|
|
|
|
if (B == Dst)
|
|
std::swap(A, B);
|
|
assert(Dst == A);
|
|
|
|
VNInfo *Other = LR->valno;
|
|
if (!Other->isDefByCopy())
|
|
return false;
|
|
const MachineInstr *OtherMI = Other->getCopy();
|
|
|
|
if (!OtherMI->isFullCopy())
|
|
return false;
|
|
|
|
unsigned OtherDst = OtherMI->getOperand(0).getReg();
|
|
unsigned OtherSrc = OtherMI->getOperand(1).getReg();
|
|
|
|
if (!TargetRegisterInfo::isVirtualRegister(OtherSrc) ||
|
|
!TargetRegisterInfo::isVirtualRegister(OtherDst))
|
|
return false;
|
|
|
|
assert(OtherDst == B);
|
|
|
|
if (Src != OtherSrc)
|
|
return false;
|
|
|
|
// If the copies use two different value numbers of X, we cannot merge
|
|
// A and B.
|
|
LiveInterval &SrcInt = li.getInterval(Src);
|
|
// getVNInfoBefore returns NULL for undef copies. In this case, the
|
|
// optimization is still safe.
|
|
if (SrcInt.getVNInfoBefore(Other->def) != SrcInt.getVNInfoBefore(VNI->def))
|
|
return false;
|
|
|
|
DupCopies.push_back(MI);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// JoinIntervals - Attempt to join these two intervals. On failure, this
|
|
/// returns false.
|
|
bool RegisterCoalescer::JoinIntervals(CoalescerPair &CP) {
|
|
LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
|
|
DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
|
|
|
|
// If a live interval is a physical register, check for interference with any
|
|
// aliases. The interference check implemented here is a bit more conservative
|
|
// than the full interfeence check below. We allow overlapping live ranges
|
|
// only when one is a copy of the other.
|
|
if (CP.isPhys()) {
|
|
for (const unsigned *AS = TRI->getAliasSet(CP.getDstReg()); *AS; ++AS){
|
|
if (!LIS->hasInterval(*AS))
|
|
continue;
|
|
const LiveInterval &LHS = LIS->getInterval(*AS);
|
|
LiveInterval::const_iterator LI = LHS.begin();
|
|
for (LiveInterval::const_iterator RI = RHS.begin(), RE = RHS.end();
|
|
RI != RE; ++RI) {
|
|
LI = std::lower_bound(LI, LHS.end(), RI->start);
|
|
// Does LHS have an overlapping live range starting before RI?
|
|
if ((LI != LHS.begin() && LI[-1].end > RI->start) &&
|
|
(RI->start != RI->valno->def ||
|
|
!CP.isCoalescable(LIS->getInstructionFromIndex(RI->start)))) {
|
|
DEBUG({
|
|
dbgs() << "\t\tInterference from alias: ";
|
|
LHS.print(dbgs(), TRI);
|
|
dbgs() << "\n\t\tOverlap at " << RI->start << " and no copy.\n";
|
|
});
|
|
return false;
|
|
}
|
|
|
|
// Check that LHS ranges beginning in this range are copies.
|
|
for (; LI != LHS.end() && LI->start < RI->end; ++LI) {
|
|
if (LI->start != LI->valno->def ||
|
|
!CP.isCoalescable(LIS->getInstructionFromIndex(LI->start))) {
|
|
DEBUG({
|
|
dbgs() << "\t\tInterference from alias: ";
|
|
LHS.print(dbgs(), TRI);
|
|
dbgs() << "\n\t\tDef at " << LI->start << " is not a copy.\n";
|
|
});
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Compute the final value assignment, assuming that the live ranges can be
|
|
// coalesced.
|
|
SmallVector<int, 16> LHSValNoAssignments;
|
|
SmallVector<int, 16> RHSValNoAssignments;
|
|
DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
|
|
DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
|
|
SmallVector<VNInfo*, 16> NewVNInfo;
|
|
|
|
SmallVector<MachineInstr*, 8> DupCopies;
|
|
|
|
LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
|
|
DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
|
|
|
|
// Loop over the value numbers of the LHS, seeing if any are defined from
|
|
// the RHS.
|
|
for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
|
|
i != e; ++i) {
|
|
VNInfo *VNI = *i;
|
|
if (VNI->isUnused() || !VNI->isDefByCopy()) // Src not defined by a copy?
|
|
continue;
|
|
|
|
// Never join with a register that has EarlyClobber redefs.
|
|
if (VNI->hasRedefByEC())
|
|
return false;
|
|
|
|
// Figure out the value # from the RHS.
|
|
LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
|
|
// The copy could be to an aliased physreg.
|
|
if (!lr) continue;
|
|
|
|
// DstReg is known to be a register in the LHS interval. If the src is
|
|
// from the RHS interval, we can use its value #.
|
|
MachineInstr *MI = VNI->getCopy();
|
|
if (!CP.isCoalescable(MI) &&
|
|
!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
|
|
continue;
|
|
|
|
LHSValsDefinedFromRHS[VNI] = lr->valno;
|
|
}
|
|
|
|
// Loop over the value numbers of the RHS, seeing if any are defined from
|
|
// the LHS.
|
|
for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
|
|
i != e; ++i) {
|
|
VNInfo *VNI = *i;
|
|
if (VNI->isUnused() || !VNI->isDefByCopy()) // Src not defined by a copy?
|
|
continue;
|
|
|
|
// Never join with a register that has EarlyClobber redefs.
|
|
if (VNI->hasRedefByEC())
|
|
return false;
|
|
|
|
// Figure out the value # from the LHS.
|
|
LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
|
|
// The copy could be to an aliased physreg.
|
|
if (!lr) continue;
|
|
|
|
// DstReg is known to be a register in the RHS interval. If the src is
|
|
// from the LHS interval, we can use its value #.
|
|
MachineInstr *MI = VNI->getCopy();
|
|
if (!CP.isCoalescable(MI) &&
|
|
!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
|
|
continue;
|
|
|
|
RHSValsDefinedFromLHS[VNI] = lr->valno;
|
|
}
|
|
|
|
LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
|
|
RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
|
|
NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
|
|
|
|
for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
|
|
i != e; ++i) {
|
|
VNInfo *VNI = *i;
|
|
unsigned VN = VNI->id;
|
|
if (LHSValNoAssignments[VN] >= 0 || VNI->isUnused())
|
|
continue;
|
|
ComputeUltimateVN(VNI, NewVNInfo,
|
|
LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
|
|
LHSValNoAssignments, RHSValNoAssignments);
|
|
}
|
|
for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
|
|
i != e; ++i) {
|
|
VNInfo *VNI = *i;
|
|
unsigned VN = VNI->id;
|
|
if (RHSValNoAssignments[VN] >= 0 || VNI->isUnused())
|
|
continue;
|
|
// If this value number isn't a copy from the LHS, it's a new number.
|
|
if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
|
|
NewVNInfo.push_back(VNI);
|
|
RHSValNoAssignments[VN] = NewVNInfo.size()-1;
|
|
continue;
|
|
}
|
|
|
|
ComputeUltimateVN(VNI, NewVNInfo,
|
|
RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
|
|
RHSValNoAssignments, LHSValNoAssignments);
|
|
}
|
|
|
|
// Armed with the mappings of LHS/RHS values to ultimate values, walk the
|
|
// interval lists to see if these intervals are coalescable.
|
|
LiveInterval::const_iterator I = LHS.begin();
|
|
LiveInterval::const_iterator IE = LHS.end();
|
|
LiveInterval::const_iterator J = RHS.begin();
|
|
LiveInterval::const_iterator JE = RHS.end();
|
|
|
|
// Skip ahead until the first place of potential sharing.
|
|
if (I != IE && J != JE) {
|
|
if (I->start < J->start) {
|
|
I = std::upper_bound(I, IE, J->start);
|
|
if (I != LHS.begin()) --I;
|
|
} else if (J->start < I->start) {
|
|
J = std::upper_bound(J, JE, I->start);
|
|
if (J != RHS.begin()) --J;
|
|
}
|
|
}
|
|
|
|
while (I != IE && J != JE) {
|
|
// Determine if these two live ranges overlap.
|
|
bool Overlaps;
|
|
if (I->start < J->start) {
|
|
Overlaps = I->end > J->start;
|
|
} else {
|
|
Overlaps = J->end > I->start;
|
|
}
|
|
|
|
// If so, check value # info to determine if they are really different.
|
|
if (Overlaps) {
|
|
// If the live range overlap will map to the same value number in the
|
|
// result liverange, we can still coalesce them. If not, we can't.
|
|
if (LHSValNoAssignments[I->valno->id] !=
|
|
RHSValNoAssignments[J->valno->id])
|
|
return false;
|
|
// If it's re-defined by an early clobber somewhere in the live range,
|
|
// then conservatively abort coalescing.
|
|
if (NewVNInfo[LHSValNoAssignments[I->valno->id]]->hasRedefByEC())
|
|
return false;
|
|
}
|
|
|
|
if (I->end < J->end)
|
|
++I;
|
|
else
|
|
++J;
|
|
}
|
|
|
|
// Update kill info. Some live ranges are extended due to copy coalescing.
|
|
for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
|
|
E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
|
|
VNInfo *VNI = I->first;
|
|
unsigned LHSValID = LHSValNoAssignments[VNI->id];
|
|
if (VNI->hasPHIKill())
|
|
NewVNInfo[LHSValID]->setHasPHIKill(true);
|
|
}
|
|
|
|
// Update kill info. Some live ranges are extended due to copy coalescing.
|
|
for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
|
|
E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
|
|
VNInfo *VNI = I->first;
|
|
unsigned RHSValID = RHSValNoAssignments[VNI->id];
|
|
if (VNI->hasPHIKill())
|
|
NewVNInfo[RHSValID]->setHasPHIKill(true);
|
|
}
|
|
|
|
if (LHSValNoAssignments.empty())
|
|
LHSValNoAssignments.push_back(-1);
|
|
if (RHSValNoAssignments.empty())
|
|
RHSValNoAssignments.push_back(-1);
|
|
|
|
SmallVector<unsigned, 8> SourceRegisters;
|
|
for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
|
|
E = DupCopies.end(); I != E; ++I) {
|
|
MachineInstr *MI = *I;
|
|
|
|
// We have pretended that the assignment to B in
|
|
// A = X
|
|
// B = X
|
|
// was actually a copy from A. Now that we decided to coalesce A and B,
|
|
// transform the code into
|
|
// A = X
|
|
// X = X
|
|
// and mark the X as coalesced to keep the illusion.
|
|
unsigned Src = MI->getOperand(1).getReg();
|
|
SourceRegisters.push_back(Src);
|
|
MI->getOperand(0).substVirtReg(Src, 0, *TRI);
|
|
|
|
markAsJoined(MI);
|
|
}
|
|
|
|
// If B = X was the last use of X in a liverange, we have to shrink it now
|
|
// that B = X is gone.
|
|
for (SmallVector<unsigned, 8>::iterator I = SourceRegisters.begin(),
|
|
E = SourceRegisters.end(); I != E; ++I) {
|
|
LIS->shrinkToUses(&LIS->getInterval(*I));
|
|
}
|
|
|
|
// If we get here, we know that we can coalesce the live ranges. Ask the
|
|
// intervals to coalesce themselves now.
|
|
LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
|
|
MRI);
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
// DepthMBBCompare - Comparison predicate that sort first based on the loop
|
|
// depth of the basic block (the unsigned), and then on the MBB number.
|
|
struct DepthMBBCompare {
|
|
typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
|
|
bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
|
|
// Deeper loops first
|
|
if (LHS.first != RHS.first)
|
|
return LHS.first > RHS.first;
|
|
|
|
// Prefer blocks that are more connected in the CFG. This takes care of
|
|
// the most difficult copies first while intervals are short.
|
|
unsigned cl = LHS.second->pred_size() + LHS.second->succ_size();
|
|
unsigned cr = RHS.second->pred_size() + RHS.second->succ_size();
|
|
if (cl != cr)
|
|
return cl > cr;
|
|
|
|
// As a last resort, sort by block number.
|
|
return LHS.second->getNumber() < RHS.second->getNumber();
|
|
}
|
|
};
|
|
}
|
|
|
|
void RegisterCoalescer::CopyCoalesceInMBB(MachineBasicBlock *MBB,
|
|
std::vector<MachineInstr*> &TryAgain) {
|
|
DEBUG(dbgs() << MBB->getName() << ":\n");
|
|
|
|
SmallVector<MachineInstr*, 8> VirtCopies;
|
|
SmallVector<MachineInstr*, 8> PhysCopies;
|
|
SmallVector<MachineInstr*, 8> ImpDefCopies;
|
|
for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
|
|
MII != E;) {
|
|
MachineInstr *Inst = MII++;
|
|
|
|
// If this isn't a copy nor a extract_subreg, we can't join intervals.
|
|
unsigned SrcReg, DstReg;
|
|
if (Inst->isCopy()) {
|
|
DstReg = Inst->getOperand(0).getReg();
|
|
SrcReg = Inst->getOperand(1).getReg();
|
|
} else if (Inst->isSubregToReg()) {
|
|
DstReg = Inst->getOperand(0).getReg();
|
|
SrcReg = Inst->getOperand(2).getReg();
|
|
} else
|
|
continue;
|
|
|
|
bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
|
|
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
|
|
if (LIS->hasInterval(SrcReg) && LIS->getInterval(SrcReg).empty())
|
|
ImpDefCopies.push_back(Inst);
|
|
else if (SrcIsPhys || DstIsPhys)
|
|
PhysCopies.push_back(Inst);
|
|
else
|
|
VirtCopies.push_back(Inst);
|
|
}
|
|
|
|
// Try coalescing implicit copies and insert_subreg <undef> first,
|
|
// followed by copies to / from physical registers, then finally copies
|
|
// from virtual registers to virtual registers.
|
|
for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) {
|
|
MachineInstr *TheCopy = ImpDefCopies[i];
|
|
bool Again = false;
|
|
if (!JoinCopy(TheCopy, Again))
|
|
if (Again)
|
|
TryAgain.push_back(TheCopy);
|
|
}
|
|
for (unsigned i = 0, e = PhysCopies.size(); i != e; ++i) {
|
|
MachineInstr *TheCopy = PhysCopies[i];
|
|
bool Again = false;
|
|
if (!JoinCopy(TheCopy, Again))
|
|
if (Again)
|
|
TryAgain.push_back(TheCopy);
|
|
}
|
|
for (unsigned i = 0, e = VirtCopies.size(); i != e; ++i) {
|
|
MachineInstr *TheCopy = VirtCopies[i];
|
|
bool Again = false;
|
|
if (!JoinCopy(TheCopy, Again))
|
|
if (Again)
|
|
TryAgain.push_back(TheCopy);
|
|
}
|
|
}
|
|
|
|
void RegisterCoalescer::joinIntervals() {
|
|
DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
|
|
|
|
std::vector<MachineInstr*> TryAgainList;
|
|
if (Loops->empty()) {
|
|
// If there are no loops in the function, join intervals in function order.
|
|
for (MachineFunction::iterator I = MF->begin(), E = MF->end();
|
|
I != E; ++I)
|
|
CopyCoalesceInMBB(I, TryAgainList);
|
|
} else {
|
|
// Otherwise, join intervals in inner loops before other intervals.
|
|
// Unfortunately we can't just iterate over loop hierarchy here because
|
|
// there may be more MBB's than BB's. Collect MBB's for sorting.
|
|
|
|
// Join intervals in the function prolog first. We want to join physical
|
|
// registers with virtual registers before the intervals got too long.
|
|
std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
|
|
for (MachineFunction::iterator I = MF->begin(), E = MF->end();I != E;++I){
|
|
MachineBasicBlock *MBB = I;
|
|
MBBs.push_back(std::make_pair(Loops->getLoopDepth(MBB), I));
|
|
}
|
|
|
|
// Sort by loop depth.
|
|
std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
|
|
|
|
// Finally, join intervals in loop nest order.
|
|
for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
|
|
CopyCoalesceInMBB(MBBs[i].second, TryAgainList);
|
|
}
|
|
|
|
// Joining intervals can allow other intervals to be joined. Iteratively join
|
|
// until we make no progress.
|
|
bool ProgressMade = true;
|
|
while (ProgressMade) {
|
|
ProgressMade = false;
|
|
|
|
for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
|
|
MachineInstr *&TheCopy = TryAgainList[i];
|
|
if (!TheCopy)
|
|
continue;
|
|
|
|
bool Again = false;
|
|
bool Success = JoinCopy(TheCopy, Again);
|
|
if (Success || !Again) {
|
|
TheCopy= 0; // Mark this one as done.
|
|
ProgressMade = true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void RegisterCoalescer::releaseMemory() {
|
|
JoinedCopies.clear();
|
|
ReMatCopies.clear();
|
|
ReMatDefs.clear();
|
|
}
|
|
|
|
bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
|
|
MF = &fn;
|
|
MRI = &fn.getRegInfo();
|
|
TM = &fn.getTarget();
|
|
TRI = TM->getRegisterInfo();
|
|
TII = TM->getInstrInfo();
|
|
LIS = &getAnalysis<LiveIntervals>();
|
|
LDV = &getAnalysis<LiveDebugVariables>();
|
|
AA = &getAnalysis<AliasAnalysis>();
|
|
Loops = &getAnalysis<MachineLoopInfo>();
|
|
|
|
DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
|
|
<< "********** Function: "
|
|
<< ((Value*)MF->getFunction())->getName() << '\n');
|
|
|
|
if (VerifyCoalescing)
|
|
MF->verify(this, "Before register coalescing");
|
|
|
|
RegClassInfo.runOnMachineFunction(fn);
|
|
|
|
// Join (coalesce) intervals if requested.
|
|
if (EnableJoining) {
|
|
joinIntervals();
|
|
DEBUG({
|
|
dbgs() << "********** INTERVALS POST JOINING **********\n";
|
|
for (LiveIntervals::iterator I = LIS->begin(), E = LIS->end();
|
|
I != E; ++I){
|
|
I->second->print(dbgs(), TRI);
|
|
dbgs() << "\n";
|
|
}
|
|
});
|
|
}
|
|
|
|
// Perform a final pass over the instructions and compute spill weights
|
|
// and remove identity moves.
|
|
SmallVector<unsigned, 4> DeadDefs, InflateRegs;
|
|
for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
|
|
mbbi != mbbe; ++mbbi) {
|
|
MachineBasicBlock* mbb = mbbi;
|
|
for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
|
|
mii != mie; ) {
|
|
MachineInstr *MI = mii;
|
|
if (JoinedCopies.count(MI)) {
|
|
// Delete all coalesced copies.
|
|
bool DoDelete = true;
|
|
assert(MI->isCopyLike() && "Unrecognized copy instruction");
|
|
unsigned SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg();
|
|
unsigned DstReg = MI->getOperand(0).getReg();
|
|
|
|
// Collect candidates for register class inflation.
|
|
if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
|
|
RegClassInfo.isProperSubClass(MRI->getRegClass(SrcReg)))
|
|
InflateRegs.push_back(SrcReg);
|
|
if (TargetRegisterInfo::isVirtualRegister(DstReg) &&
|
|
RegClassInfo.isProperSubClass(MRI->getRegClass(DstReg)))
|
|
InflateRegs.push_back(DstReg);
|
|
|
|
if (TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
|
|
MI->getNumOperands() > 2)
|
|
// Do not delete extract_subreg, insert_subreg of physical
|
|
// registers unless the definition is dead. e.g.
|
|
// %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1
|
|
// or else the scavenger may complain. LowerSubregs will
|
|
// delete them later.
|
|
DoDelete = false;
|
|
|
|
if (MI->allDefsAreDead()) {
|
|
if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
|
|
LIS->hasInterval(SrcReg))
|
|
LIS->shrinkToUses(&LIS->getInterval(SrcReg));
|
|
DoDelete = true;
|
|
}
|
|
if (!DoDelete) {
|
|
// We need the instruction to adjust liveness, so make it a KILL.
|
|
if (MI->isSubregToReg()) {
|
|
MI->RemoveOperand(3);
|
|
MI->RemoveOperand(1);
|
|
}
|
|
MI->setDesc(TII->get(TargetOpcode::KILL));
|
|
mii = llvm::next(mii);
|
|
} else {
|
|
LIS->RemoveMachineInstrFromMaps(MI);
|
|
mii = mbbi->erase(mii);
|
|
++numPeep;
|
|
}
|
|
continue;
|
|
}
|
|
|
|
// Now check if this is a remat'ed def instruction which is now dead.
|
|
if (ReMatDefs.count(MI)) {
|
|
bool isDead = true;
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
const MachineOperand &MO = MI->getOperand(i);
|
|
if (!MO.isReg())
|
|
continue;
|
|
unsigned Reg = MO.getReg();
|
|
if (!Reg)
|
|
continue;
|
|
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
|
|
DeadDefs.push_back(Reg);
|
|
// Remat may also enable register class inflation.
|
|
if (RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)))
|
|
InflateRegs.push_back(Reg);
|
|
}
|
|
if (MO.isDead())
|
|
continue;
|
|
if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
|
|
!MRI->use_nodbg_empty(Reg)) {
|
|
isDead = false;
|
|
break;
|
|
}
|
|
}
|
|
if (isDead) {
|
|
while (!DeadDefs.empty()) {
|
|
unsigned DeadDef = DeadDefs.back();
|
|
DeadDefs.pop_back();
|
|
RemoveDeadDef(LIS->getInterval(DeadDef), MI);
|
|
}
|
|
LIS->RemoveMachineInstrFromMaps(mii);
|
|
mii = mbbi->erase(mii);
|
|
continue;
|
|
} else
|
|
DeadDefs.clear();
|
|
}
|
|
|
|
++mii;
|
|
|
|
// Check for now unnecessary kill flags.
|
|
if (LIS->isNotInMIMap(MI)) continue;
|
|
SlotIndex DefIdx = LIS->getInstructionIndex(MI).getDefIndex();
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (!MO.isReg() || !MO.isKill()) continue;
|
|
unsigned reg = MO.getReg();
|
|
if (!reg || !LIS->hasInterval(reg)) continue;
|
|
if (!LIS->getInterval(reg).killedAt(DefIdx)) {
|
|
MO.setIsKill(false);
|
|
continue;
|
|
}
|
|
// When leaving a kill flag on a physreg, check if any subregs should
|
|
// remain alive.
|
|
if (!TargetRegisterInfo::isPhysicalRegister(reg))
|
|
continue;
|
|
for (const unsigned *SR = TRI->getSubRegisters(reg);
|
|
unsigned S = *SR; ++SR)
|
|
if (LIS->hasInterval(S) && LIS->getInterval(S).liveAt(DefIdx))
|
|
MI->addRegisterDefined(S, TRI);
|
|
}
|
|
}
|
|
}
|
|
|
|
// After deleting a lot of copies, register classes may be less constrained.
|
|
// Removing sub-register opreands may alow GR32_ABCD -> GR32 and DPR_VFP2 ->
|
|
// DPR inflation.
|
|
array_pod_sort(InflateRegs.begin(), InflateRegs.end());
|
|
InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
|
|
InflateRegs.end());
|
|
DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
|
|
for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
|
|
unsigned Reg = InflateRegs[i];
|
|
if (MRI->reg_nodbg_empty(Reg))
|
|
continue;
|
|
if (MRI->recomputeRegClass(Reg, *TM)) {
|
|
DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
|
|
<< MRI->getRegClass(Reg)->getName() << '\n');
|
|
++NumInflated;
|
|
}
|
|
}
|
|
|
|
DEBUG(dump());
|
|
DEBUG(LDV->dump());
|
|
if (VerifyCoalescing)
|
|
MF->verify(this, "After register coalescing");
|
|
return true;
|
|
}
|
|
|
|
/// print - Implement the dump method.
|
|
void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {
|
|
LIS->print(O, m);
|
|
}
|