198 lines
6.4 KiB
C++
198 lines
6.4 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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#include "llvm/CodeGen/RegisterCoalescer.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/Pass.h"
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using namespace llvm;
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// Register the RegisterCoalescer interface, providing a nice name to refer to.
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static RegisterAnalysisGroup<RegisterCoalescer> Z("Register Coalescer");
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char RegisterCoalescer::ID = 0;
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// RegisterCoalescer destructor: DO NOT move this to the header file
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// for RegisterCoalescer or else clients of the RegisterCoalescer
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// class may not depend on the RegisterCoalescer.o file in the current
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// .a file, causing alias analysis support to not be included in the
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// tool correctly!
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//
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RegisterCoalescer::~RegisterCoalescer() {}
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unsigned CoalescerPair::compose(unsigned a, unsigned b) const {
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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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bool CoalescerPair::isMoveInstr(const MachineInstr *MI,
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unsigned &Src, unsigned &Dst,
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unsigned &SrcSub, unsigned &DstSub) const {
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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(MI->getOperand(0).getSubReg(), 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 if (!tii_.isMoveInstr(*MI, Src, Dst, SrcSub, DstSub)) {
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return false;
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}
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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(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 (!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_ = 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(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(subIdx_, SrcSub) == DstSub;
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}
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}
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// Because of the way .a files work, we must force the SimpleRC
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// implementation to be pulled in if the RegisterCoalescer classes are
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// pulled in. Otherwise we run the risk of RegisterCoalescer being
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// used, but the default implementation not being linked into the tool
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// that uses it.
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DEFINING_FILE_FOR(RegisterCoalescer)
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