769 lines
28 KiB
C++
769 lines
28 KiB
C++
//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
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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 family of functions perform manipulations on basic blocks, and
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// instructions contained within basic blocks.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/CFG.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/MemoryDependenceAnalysis.h"
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#include "llvm/IR/Constant.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Type.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <algorithm>
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using namespace llvm;
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void llvm::DeleteDeadBlock(BasicBlock *BB) {
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assert((pred_begin(BB) == pred_end(BB) ||
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// Can delete self loop.
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BB->getSinglePredecessor() == BB) && "Block is not dead!");
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TerminatorInst *BBTerm = BB->getTerminator();
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// Loop through all of our successors and make sure they know that one
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// of their predecessors is going away.
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for (BasicBlock *Succ : BBTerm->successors())
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Succ->removePredecessor(BB);
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// Zap all the instructions in the block.
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while (!BB->empty()) {
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Instruction &I = BB->back();
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// If this instruction is used, replace uses with an arbitrary value.
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// Because control flow can't get here, we don't care what we replace the
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// value with. Note that since this block is unreachable, and all values
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// contained within it must dominate their uses, that all uses will
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// eventually be removed (they are themselves dead).
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if (!I.use_empty())
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I.replaceAllUsesWith(UndefValue::get(I.getType()));
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BB->getInstList().pop_back();
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}
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// Zap the block!
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BB->eraseFromParent();
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}
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void llvm::FoldSingleEntryPHINodes(BasicBlock *BB,
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MemoryDependenceResults *MemDep) {
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if (!isa<PHINode>(BB->begin())) return;
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while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
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if (PN->getIncomingValue(0) != PN)
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PN->replaceAllUsesWith(PN->getIncomingValue(0));
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else
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PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
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if (MemDep)
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MemDep->removeInstruction(PN); // Memdep updates AA itself.
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PN->eraseFromParent();
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}
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}
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bool llvm::DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI) {
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// Recursively deleting a PHI may cause multiple PHIs to be deleted
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// or RAUW'd undef, so use an array of WeakVH for the PHIs to delete.
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SmallVector<WeakVH, 8> PHIs;
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for (BasicBlock::iterator I = BB->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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PHIs.push_back(PN);
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bool Changed = false;
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for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
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if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
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Changed |= RecursivelyDeleteDeadPHINode(PN, TLI);
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return Changed;
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}
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bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, DominatorTree *DT,
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LoopInfo *LI,
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MemoryDependenceResults *MemDep) {
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// Don't merge away blocks who have their address taken.
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if (BB->hasAddressTaken()) return false;
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// Can't merge if there are multiple predecessors, or no predecessors.
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BasicBlock *PredBB = BB->getUniquePredecessor();
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if (!PredBB) return false;
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// Don't break self-loops.
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if (PredBB == BB) return false;
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// Don't break unwinding instructions.
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if (PredBB->getTerminator()->isExceptional())
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return false;
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succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
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BasicBlock *OnlySucc = BB;
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for (; SI != SE; ++SI)
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if (*SI != OnlySucc) {
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OnlySucc = nullptr; // There are multiple distinct successors!
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break;
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}
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// Can't merge if there are multiple successors.
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if (!OnlySucc) return false;
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// Can't merge if there is PHI loop.
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for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
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if (PHINode *PN = dyn_cast<PHINode>(BI)) {
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for (Value *IncValue : PN->incoming_values())
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if (IncValue == PN)
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return false;
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} else
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break;
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}
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// Begin by getting rid of unneeded PHIs.
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if (isa<PHINode>(BB->front()))
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FoldSingleEntryPHINodes(BB, MemDep);
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// Delete the unconditional branch from the predecessor...
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PredBB->getInstList().pop_back();
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// Make all PHI nodes that referred to BB now refer to Pred as their
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// source...
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BB->replaceAllUsesWith(PredBB);
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// Move all definitions in the successor to the predecessor...
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PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
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// Inherit predecessors name if it exists.
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if (!PredBB->hasName())
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PredBB->takeName(BB);
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// Finally, erase the old block and update dominator info.
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if (DT)
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if (DomTreeNode *DTN = DT->getNode(BB)) {
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DomTreeNode *PredDTN = DT->getNode(PredBB);
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SmallVector<DomTreeNode *, 8> Children(DTN->begin(), DTN->end());
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for (DomTreeNode *DI : Children)
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DT->changeImmediateDominator(DI, PredDTN);
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DT->eraseNode(BB);
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}
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if (LI)
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LI->removeBlock(BB);
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if (MemDep)
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MemDep->invalidateCachedPredecessors();
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BB->eraseFromParent();
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return true;
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}
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void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Value *V) {
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Instruction &I = *BI;
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// Replaces all of the uses of the instruction with uses of the value
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I.replaceAllUsesWith(V);
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// Make sure to propagate a name if there is one already.
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if (I.hasName() && !V->hasName())
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V->takeName(&I);
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// Delete the unnecessary instruction now...
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BI = BIL.erase(BI);
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}
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void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Instruction *I) {
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assert(I->getParent() == nullptr &&
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"ReplaceInstWithInst: Instruction already inserted into basic block!");
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// Copy debug location to newly added instruction, if it wasn't already set
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// by the caller.
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if (!I->getDebugLoc())
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I->setDebugLoc(BI->getDebugLoc());
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// Insert the new instruction into the basic block...
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BasicBlock::iterator New = BIL.insert(BI, I);
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// Replace all uses of the old instruction, and delete it.
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ReplaceInstWithValue(BIL, BI, I);
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// Move BI back to point to the newly inserted instruction
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BI = New;
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}
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void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
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BasicBlock::iterator BI(From);
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ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
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}
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BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, DominatorTree *DT,
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LoopInfo *LI) {
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unsigned SuccNum = GetSuccessorNumber(BB, Succ);
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// If this is a critical edge, let SplitCriticalEdge do it.
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TerminatorInst *LatchTerm = BB->getTerminator();
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if (SplitCriticalEdge(LatchTerm, SuccNum, CriticalEdgeSplittingOptions(DT, LI)
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.setPreserveLCSSA()))
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return LatchTerm->getSuccessor(SuccNum);
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// If the edge isn't critical, then BB has a single successor or Succ has a
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// single pred. Split the block.
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if (BasicBlock *SP = Succ->getSinglePredecessor()) {
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// If the successor only has a single pred, split the top of the successor
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// block.
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assert(SP == BB && "CFG broken");
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SP = nullptr;
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return SplitBlock(Succ, &Succ->front(), DT, LI);
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}
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// Otherwise, if BB has a single successor, split it at the bottom of the
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// block.
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assert(BB->getTerminator()->getNumSuccessors() == 1 &&
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"Should have a single succ!");
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return SplitBlock(BB, BB->getTerminator(), DT, LI);
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}
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unsigned
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llvm::SplitAllCriticalEdges(Function &F,
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const CriticalEdgeSplittingOptions &Options) {
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unsigned NumBroken = 0;
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for (BasicBlock &BB : F) {
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TerminatorInst *TI = BB.getTerminator();
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if (TI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(TI))
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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if (SplitCriticalEdge(TI, i, Options))
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++NumBroken;
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}
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return NumBroken;
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}
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BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt,
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DominatorTree *DT, LoopInfo *LI) {
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BasicBlock::iterator SplitIt = SplitPt->getIterator();
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while (isa<PHINode>(SplitIt) || SplitIt->isEHPad())
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++SplitIt;
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BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
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// The new block lives in whichever loop the old one did. This preserves
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// LCSSA as well, because we force the split point to be after any PHI nodes.
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if (LI)
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if (Loop *L = LI->getLoopFor(Old))
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L->addBasicBlockToLoop(New, *LI);
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if (DT)
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// Old dominates New. New node dominates all other nodes dominated by Old.
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if (DomTreeNode *OldNode = DT->getNode(Old)) {
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std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
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DomTreeNode *NewNode = DT->addNewBlock(New, Old);
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for (DomTreeNode *I : Children)
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DT->changeImmediateDominator(I, NewNode);
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}
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return New;
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}
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/// Update DominatorTree, LoopInfo, and LCCSA analysis information.
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static void UpdateAnalysisInformation(BasicBlock *OldBB, BasicBlock *NewBB,
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ArrayRef<BasicBlock *> Preds,
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DominatorTree *DT, LoopInfo *LI,
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bool PreserveLCSSA, bool &HasLoopExit) {
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// Update dominator tree if available.
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if (DT)
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DT->splitBlock(NewBB);
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// The rest of the logic is only relevant for updating the loop structures.
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if (!LI)
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return;
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Loop *L = LI->getLoopFor(OldBB);
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// If we need to preserve loop analyses, collect some information about how
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// this split will affect loops.
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bool IsLoopEntry = !!L;
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bool SplitMakesNewLoopHeader = false;
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for (BasicBlock *Pred : Preds) {
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// If we need to preserve LCSSA, determine if any of the preds is a loop
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// exit.
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if (PreserveLCSSA)
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if (Loop *PL = LI->getLoopFor(Pred))
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if (!PL->contains(OldBB))
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HasLoopExit = true;
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// If we need to preserve LoopInfo, note whether any of the preds crosses
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// an interesting loop boundary.
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if (!L)
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continue;
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if (L->contains(Pred))
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IsLoopEntry = false;
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else
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SplitMakesNewLoopHeader = true;
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}
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// Unless we have a loop for OldBB, nothing else to do here.
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if (!L)
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return;
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if (IsLoopEntry) {
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// Add the new block to the nearest enclosing loop (and not an adjacent
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// loop). To find this, examine each of the predecessors and determine which
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// loops enclose them, and select the most-nested loop which contains the
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// loop containing the block being split.
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Loop *InnermostPredLoop = nullptr;
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for (BasicBlock *Pred : Preds) {
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if (Loop *PredLoop = LI->getLoopFor(Pred)) {
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// Seek a loop which actually contains the block being split (to avoid
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// adjacent loops).
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while (PredLoop && !PredLoop->contains(OldBB))
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PredLoop = PredLoop->getParentLoop();
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// Select the most-nested of these loops which contains the block.
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if (PredLoop && PredLoop->contains(OldBB) &&
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(!InnermostPredLoop ||
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InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
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InnermostPredLoop = PredLoop;
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}
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}
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if (InnermostPredLoop)
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InnermostPredLoop->addBasicBlockToLoop(NewBB, *LI);
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} else {
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L->addBasicBlockToLoop(NewBB, *LI);
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if (SplitMakesNewLoopHeader)
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L->moveToHeader(NewBB);
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}
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}
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/// Update the PHI nodes in OrigBB to include the values coming from NewBB.
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/// This also updates AliasAnalysis, if available.
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static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
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ArrayRef<BasicBlock *> Preds, BranchInst *BI,
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bool HasLoopExit) {
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// Otherwise, create a new PHI node in NewBB for each PHI node in OrigBB.
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SmallPtrSet<BasicBlock *, 16> PredSet(Preds.begin(), Preds.end());
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for (BasicBlock::iterator I = OrigBB->begin(); isa<PHINode>(I); ) {
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PHINode *PN = cast<PHINode>(I++);
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// Check to see if all of the values coming in are the same. If so, we
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// don't need to create a new PHI node, unless it's needed for LCSSA.
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Value *InVal = nullptr;
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if (!HasLoopExit) {
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InVal = PN->getIncomingValueForBlock(Preds[0]);
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
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if (!PredSet.count(PN->getIncomingBlock(i)))
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continue;
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if (!InVal)
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InVal = PN->getIncomingValue(i);
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else if (InVal != PN->getIncomingValue(i)) {
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InVal = nullptr;
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break;
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}
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}
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}
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if (InVal) {
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// If all incoming values for the new PHI would be the same, just don't
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// make a new PHI. Instead, just remove the incoming values from the old
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// PHI.
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// NOTE! This loop walks backwards for a reason! First off, this minimizes
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// the cost of removal if we end up removing a large number of values, and
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// second off, this ensures that the indices for the incoming values
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// aren't invalidated when we remove one.
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for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i)
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if (PredSet.count(PN->getIncomingBlock(i)))
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PN->removeIncomingValue(i, false);
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// Add an incoming value to the PHI node in the loop for the preheader
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// edge.
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PN->addIncoming(InVal, NewBB);
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continue;
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}
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// If the values coming into the block are not the same, we need a new
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// PHI.
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// Create the new PHI node, insert it into NewBB at the end of the block
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PHINode *NewPHI =
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PHINode::Create(PN->getType(), Preds.size(), PN->getName() + ".ph", BI);
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// NOTE! This loop walks backwards for a reason! First off, this minimizes
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// the cost of removal if we end up removing a large number of values, and
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// second off, this ensures that the indices for the incoming values aren't
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// invalidated when we remove one.
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for (int64_t i = PN->getNumIncomingValues() - 1; i >= 0; --i) {
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BasicBlock *IncomingBB = PN->getIncomingBlock(i);
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if (PredSet.count(IncomingBB)) {
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Value *V = PN->removeIncomingValue(i, false);
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NewPHI->addIncoming(V, IncomingBB);
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}
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}
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PN->addIncoming(NewPHI, NewBB);
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}
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}
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BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
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ArrayRef<BasicBlock *> Preds,
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const char *Suffix, DominatorTree *DT,
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LoopInfo *LI, bool PreserveLCSSA) {
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// Do not attempt to split that which cannot be split.
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if (!BB->canSplitPredecessors())
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return nullptr;
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// For the landingpads we need to act a bit differently.
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// Delegate this work to the SplitLandingPadPredecessors.
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if (BB->isLandingPad()) {
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SmallVector<BasicBlock*, 2> NewBBs;
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std::string NewName = std::string(Suffix) + ".split-lp";
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SplitLandingPadPredecessors(BB, Preds, Suffix, NewName.c_str(), NewBBs, DT,
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LI, PreserveLCSSA);
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return NewBBs[0];
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}
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// Create new basic block, insert right before the original block.
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BasicBlock *NewBB = BasicBlock::Create(
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BB->getContext(), BB->getName() + Suffix, BB->getParent(), BB);
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// The new block unconditionally branches to the old block.
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BranchInst *BI = BranchInst::Create(BB, NewBB);
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BI->setDebugLoc(BB->getFirstNonPHI()->getDebugLoc());
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// Move the edges from Preds to point to NewBB instead of BB.
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for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
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// This is slightly more strict than necessary; the minimum requirement
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// is that there be no more than one indirectbr branching to BB. And
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// all BlockAddress uses would need to be updated.
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assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
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"Cannot split an edge from an IndirectBrInst");
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Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
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}
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// Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
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// node becomes an incoming value for BB's phi node. However, if the Preds
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// list is empty, we need to insert dummy entries into the PHI nodes in BB to
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// account for the newly created predecessor.
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if (Preds.size() == 0) {
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// Insert dummy values as the incoming value.
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for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
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cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
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return NewBB;
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}
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// Update DominatorTree, LoopInfo, and LCCSA analysis information.
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bool HasLoopExit = false;
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UpdateAnalysisInformation(BB, NewBB, Preds, DT, LI, PreserveLCSSA,
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HasLoopExit);
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// Update the PHI nodes in BB with the values coming from NewBB.
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UpdatePHINodes(BB, NewBB, Preds, BI, HasLoopExit);
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return NewBB;
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}
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void llvm::SplitLandingPadPredecessors(BasicBlock *OrigBB,
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ArrayRef<BasicBlock *> Preds,
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const char *Suffix1, const char *Suffix2,
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SmallVectorImpl<BasicBlock *> &NewBBs,
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DominatorTree *DT, LoopInfo *LI,
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|
bool PreserveLCSSA) {
|
|
assert(OrigBB->isLandingPad() && "Trying to split a non-landing pad!");
|
|
|
|
// Create a new basic block for OrigBB's predecessors listed in Preds. Insert
|
|
// it right before the original block.
|
|
BasicBlock *NewBB1 = BasicBlock::Create(OrigBB->getContext(),
|
|
OrigBB->getName() + Suffix1,
|
|
OrigBB->getParent(), OrigBB);
|
|
NewBBs.push_back(NewBB1);
|
|
|
|
// The new block unconditionally branches to the old block.
|
|
BranchInst *BI1 = BranchInst::Create(OrigBB, NewBB1);
|
|
BI1->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
|
|
|
|
// Move the edges from Preds to point to NewBB1 instead of OrigBB.
|
|
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
|
|
// This is slightly more strict than necessary; the minimum requirement
|
|
// is that there be no more than one indirectbr branching to BB. And
|
|
// all BlockAddress uses would need to be updated.
|
|
assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
|
|
"Cannot split an edge from an IndirectBrInst");
|
|
Preds[i]->getTerminator()->replaceUsesOfWith(OrigBB, NewBB1);
|
|
}
|
|
|
|
bool HasLoopExit = false;
|
|
UpdateAnalysisInformation(OrigBB, NewBB1, Preds, DT, LI, PreserveLCSSA,
|
|
HasLoopExit);
|
|
|
|
// Update the PHI nodes in OrigBB with the values coming from NewBB1.
|
|
UpdatePHINodes(OrigBB, NewBB1, Preds, BI1, HasLoopExit);
|
|
|
|
// Move the remaining edges from OrigBB to point to NewBB2.
|
|
SmallVector<BasicBlock*, 8> NewBB2Preds;
|
|
for (pred_iterator i = pred_begin(OrigBB), e = pred_end(OrigBB);
|
|
i != e; ) {
|
|
BasicBlock *Pred = *i++;
|
|
if (Pred == NewBB1) continue;
|
|
assert(!isa<IndirectBrInst>(Pred->getTerminator()) &&
|
|
"Cannot split an edge from an IndirectBrInst");
|
|
NewBB2Preds.push_back(Pred);
|
|
e = pred_end(OrigBB);
|
|
}
|
|
|
|
BasicBlock *NewBB2 = nullptr;
|
|
if (!NewBB2Preds.empty()) {
|
|
// Create another basic block for the rest of OrigBB's predecessors.
|
|
NewBB2 = BasicBlock::Create(OrigBB->getContext(),
|
|
OrigBB->getName() + Suffix2,
|
|
OrigBB->getParent(), OrigBB);
|
|
NewBBs.push_back(NewBB2);
|
|
|
|
// The new block unconditionally branches to the old block.
|
|
BranchInst *BI2 = BranchInst::Create(OrigBB, NewBB2);
|
|
BI2->setDebugLoc(OrigBB->getFirstNonPHI()->getDebugLoc());
|
|
|
|
// Move the remaining edges from OrigBB to point to NewBB2.
|
|
for (BasicBlock *NewBB2Pred : NewBB2Preds)
|
|
NewBB2Pred->getTerminator()->replaceUsesOfWith(OrigBB, NewBB2);
|
|
|
|
// Update DominatorTree, LoopInfo, and LCCSA analysis information.
|
|
HasLoopExit = false;
|
|
UpdateAnalysisInformation(OrigBB, NewBB2, NewBB2Preds, DT, LI,
|
|
PreserveLCSSA, HasLoopExit);
|
|
|
|
// Update the PHI nodes in OrigBB with the values coming from NewBB2.
|
|
UpdatePHINodes(OrigBB, NewBB2, NewBB2Preds, BI2, HasLoopExit);
|
|
}
|
|
|
|
LandingPadInst *LPad = OrigBB->getLandingPadInst();
|
|
Instruction *Clone1 = LPad->clone();
|
|
Clone1->setName(Twine("lpad") + Suffix1);
|
|
NewBB1->getInstList().insert(NewBB1->getFirstInsertionPt(), Clone1);
|
|
|
|
if (NewBB2) {
|
|
Instruction *Clone2 = LPad->clone();
|
|
Clone2->setName(Twine("lpad") + Suffix2);
|
|
NewBB2->getInstList().insert(NewBB2->getFirstInsertionPt(), Clone2);
|
|
|
|
// Create a PHI node for the two cloned landingpad instructions only
|
|
// if the original landingpad instruction has some uses.
|
|
if (!LPad->use_empty()) {
|
|
assert(!LPad->getType()->isTokenTy() &&
|
|
"Split cannot be applied if LPad is token type. Otherwise an "
|
|
"invalid PHINode of token type would be created.");
|
|
PHINode *PN = PHINode::Create(LPad->getType(), 2, "lpad.phi", LPad);
|
|
PN->addIncoming(Clone1, NewBB1);
|
|
PN->addIncoming(Clone2, NewBB2);
|
|
LPad->replaceAllUsesWith(PN);
|
|
}
|
|
LPad->eraseFromParent();
|
|
} else {
|
|
// There is no second clone. Just replace the landing pad with the first
|
|
// clone.
|
|
LPad->replaceAllUsesWith(Clone1);
|
|
LPad->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
|
|
BasicBlock *Pred) {
|
|
Instruction *UncondBranch = Pred->getTerminator();
|
|
// Clone the return and add it to the end of the predecessor.
|
|
Instruction *NewRet = RI->clone();
|
|
Pred->getInstList().push_back(NewRet);
|
|
|
|
// If the return instruction returns a value, and if the value was a
|
|
// PHI node in "BB", propagate the right value into the return.
|
|
for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
|
|
i != e; ++i) {
|
|
Value *V = *i;
|
|
Instruction *NewBC = nullptr;
|
|
if (BitCastInst *BCI = dyn_cast<BitCastInst>(V)) {
|
|
// Return value might be bitcasted. Clone and insert it before the
|
|
// return instruction.
|
|
V = BCI->getOperand(0);
|
|
NewBC = BCI->clone();
|
|
Pred->getInstList().insert(NewRet->getIterator(), NewBC);
|
|
*i = NewBC;
|
|
}
|
|
if (PHINode *PN = dyn_cast<PHINode>(V)) {
|
|
if (PN->getParent() == BB) {
|
|
if (NewBC)
|
|
NewBC->setOperand(0, PN->getIncomingValueForBlock(Pred));
|
|
else
|
|
*i = PN->getIncomingValueForBlock(Pred);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Update any PHI nodes in the returning block to realize that we no
|
|
// longer branch to them.
|
|
BB->removePredecessor(Pred);
|
|
UncondBranch->eraseFromParent();
|
|
return cast<ReturnInst>(NewRet);
|
|
}
|
|
|
|
TerminatorInst *
|
|
llvm::SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
|
|
bool Unreachable, MDNode *BranchWeights,
|
|
DominatorTree *DT, LoopInfo *LI) {
|
|
BasicBlock *Head = SplitBefore->getParent();
|
|
BasicBlock *Tail = Head->splitBasicBlock(SplitBefore->getIterator());
|
|
TerminatorInst *HeadOldTerm = Head->getTerminator();
|
|
LLVMContext &C = Head->getContext();
|
|
BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
|
|
TerminatorInst *CheckTerm;
|
|
if (Unreachable)
|
|
CheckTerm = new UnreachableInst(C, ThenBlock);
|
|
else
|
|
CheckTerm = BranchInst::Create(Tail, ThenBlock);
|
|
CheckTerm->setDebugLoc(SplitBefore->getDebugLoc());
|
|
BranchInst *HeadNewTerm =
|
|
BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cond);
|
|
HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
|
|
ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
|
|
|
|
if (DT) {
|
|
if (DomTreeNode *OldNode = DT->getNode(Head)) {
|
|
std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
|
|
|
|
DomTreeNode *NewNode = DT->addNewBlock(Tail, Head);
|
|
for (DomTreeNode *Child : Children)
|
|
DT->changeImmediateDominator(Child, NewNode);
|
|
|
|
// Head dominates ThenBlock.
|
|
DT->addNewBlock(ThenBlock, Head);
|
|
}
|
|
}
|
|
|
|
if (LI) {
|
|
Loop *L = LI->getLoopFor(Head);
|
|
L->addBasicBlockToLoop(ThenBlock, *LI);
|
|
L->addBasicBlockToLoop(Tail, *LI);
|
|
}
|
|
|
|
return CheckTerm;
|
|
}
|
|
|
|
void llvm::SplitBlockAndInsertIfThenElse(Value *Cond, Instruction *SplitBefore,
|
|
TerminatorInst **ThenTerm,
|
|
TerminatorInst **ElseTerm,
|
|
MDNode *BranchWeights) {
|
|
BasicBlock *Head = SplitBefore->getParent();
|
|
BasicBlock *Tail = Head->splitBasicBlock(SplitBefore->getIterator());
|
|
TerminatorInst *HeadOldTerm = Head->getTerminator();
|
|
LLVMContext &C = Head->getContext();
|
|
BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
|
|
BasicBlock *ElseBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
|
|
*ThenTerm = BranchInst::Create(Tail, ThenBlock);
|
|
(*ThenTerm)->setDebugLoc(SplitBefore->getDebugLoc());
|
|
*ElseTerm = BranchInst::Create(Tail, ElseBlock);
|
|
(*ElseTerm)->setDebugLoc(SplitBefore->getDebugLoc());
|
|
BranchInst *HeadNewTerm =
|
|
BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/ElseBlock, Cond);
|
|
HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
|
|
ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
|
|
}
|
|
|
|
|
|
Value *llvm::GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
|
|
BasicBlock *&IfFalse) {
|
|
PHINode *SomePHI = dyn_cast<PHINode>(BB->begin());
|
|
BasicBlock *Pred1 = nullptr;
|
|
BasicBlock *Pred2 = nullptr;
|
|
|
|
if (SomePHI) {
|
|
if (SomePHI->getNumIncomingValues() != 2)
|
|
return nullptr;
|
|
Pred1 = SomePHI->getIncomingBlock(0);
|
|
Pred2 = SomePHI->getIncomingBlock(1);
|
|
} else {
|
|
pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
|
|
if (PI == PE) // No predecessor
|
|
return nullptr;
|
|
Pred1 = *PI++;
|
|
if (PI == PE) // Only one predecessor
|
|
return nullptr;
|
|
Pred2 = *PI++;
|
|
if (PI != PE) // More than two predecessors
|
|
return nullptr;
|
|
}
|
|
|
|
// We can only handle branches. Other control flow will be lowered to
|
|
// branches if possible anyway.
|
|
BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator());
|
|
BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator());
|
|
if (!Pred1Br || !Pred2Br)
|
|
return nullptr;
|
|
|
|
// Eliminate code duplication by ensuring that Pred1Br is conditional if
|
|
// either are.
|
|
if (Pred2Br->isConditional()) {
|
|
// If both branches are conditional, we don't have an "if statement". In
|
|
// reality, we could transform this case, but since the condition will be
|
|
// required anyway, we stand no chance of eliminating it, so the xform is
|
|
// probably not profitable.
|
|
if (Pred1Br->isConditional())
|
|
return nullptr;
|
|
|
|
std::swap(Pred1, Pred2);
|
|
std::swap(Pred1Br, Pred2Br);
|
|
}
|
|
|
|
if (Pred1Br->isConditional()) {
|
|
// The only thing we have to watch out for here is to make sure that Pred2
|
|
// doesn't have incoming edges from other blocks. If it does, the condition
|
|
// doesn't dominate BB.
|
|
if (!Pred2->getSinglePredecessor())
|
|
return nullptr;
|
|
|
|
// If we found a conditional branch predecessor, make sure that it branches
|
|
// to BB and Pred2Br. If it doesn't, this isn't an "if statement".
|
|
if (Pred1Br->getSuccessor(0) == BB &&
|
|
Pred1Br->getSuccessor(1) == Pred2) {
|
|
IfTrue = Pred1;
|
|
IfFalse = Pred2;
|
|
} else if (Pred1Br->getSuccessor(0) == Pred2 &&
|
|
Pred1Br->getSuccessor(1) == BB) {
|
|
IfTrue = Pred2;
|
|
IfFalse = Pred1;
|
|
} else {
|
|
// We know that one arm of the conditional goes to BB, so the other must
|
|
// go somewhere unrelated, and this must not be an "if statement".
|
|
return nullptr;
|
|
}
|
|
|
|
return Pred1Br->getCondition();
|
|
}
|
|
|
|
// Ok, if we got here, both predecessors end with an unconditional branch to
|
|
// BB. Don't panic! If both blocks only have a single (identical)
|
|
// predecessor, and THAT is a conditional branch, then we're all ok!
|
|
BasicBlock *CommonPred = Pred1->getSinglePredecessor();
|
|
if (CommonPred == nullptr || CommonPred != Pred2->getSinglePredecessor())
|
|
return nullptr;
|
|
|
|
// Otherwise, if this is a conditional branch, then we can use it!
|
|
BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator());
|
|
if (!BI) return nullptr;
|
|
|
|
assert(BI->isConditional() && "Two successors but not conditional?");
|
|
if (BI->getSuccessor(0) == Pred1) {
|
|
IfTrue = Pred1;
|
|
IfFalse = Pred2;
|
|
} else {
|
|
IfTrue = Pred2;
|
|
IfFalse = Pred1;
|
|
}
|
|
return BI->getCondition();
|
|
}
|