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Sink CmpInst's to their uses to reduce register pressure.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37554 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -317,7 +317,7 @@ static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
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/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
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/// copy (e.g. it's casting from one pointer type to another, int->uint, or
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/// int->sbyte on PPC), sink it into user blocks to reduce the number of virtual
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/// registers that must be created and coallesced.
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/// registers that must be created and coalesced.
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///
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/// Return true if any changes are made.
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static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
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@ -348,7 +348,7 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
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BasicBlock *DefBB = CI->getParent();
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/// InsertedCasts - Only insert a cast in each block once.
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std::map<BasicBlock*, CastInst*> InsertedCasts;
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DenseMap<BasicBlock*, CastInst*> InsertedCasts;
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bool MadeChange = false;
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for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
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@ -383,7 +383,7 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
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MadeChange = true;
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}
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// Replace a use of the cast with a use of the new casat.
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// Replace a use of the cast with a use of the new cast.
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TheUse = InsertedCast;
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}
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@ -394,6 +394,62 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
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return MadeChange;
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}
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/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
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/// the number of virtual registers that must be created and coalesced. This is
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/// a clear win except on targets with multiple condition code registers (powerPC),
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/// where it might lose; some adjustment may be wanted there.
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///
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/// Return true if any changes are made.
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static bool OptimizeCmpExpression(CmpInst *CI){
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BasicBlock *DefBB = CI->getParent();
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/// InsertedCmp - Only insert a cmp in each block once.
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DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
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bool MadeChange = false;
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for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
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UI != E; ) {
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Use &TheUse = UI.getUse();
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Instruction *User = cast<Instruction>(*UI);
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// Preincrement use iterator so we don't invalidate it.
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++UI;
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// Don't bother for PHI nodes.
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if (isa<PHINode>(User))
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continue;
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// Figure out which BB this cmp is used in.
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BasicBlock *UserBB = User->getParent();
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// If this user is in the same block as the cmp, don't change the cmp.
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if (UserBB == DefBB) continue;
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// If we have already inserted a cmp into this block, use it.
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CmpInst *&InsertedCmp = InsertedCmps[UserBB];
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if (!InsertedCmp) {
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BasicBlock::iterator InsertPt = UserBB->begin();
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while (isa<PHINode>(InsertPt)) ++InsertPt;
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InsertedCmp =
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CmpInst::create(CI->getOpcode(), CI->getPredicate(), CI->getOperand(0),
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CI->getOperand(1), "", InsertPt);
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MadeChange = true;
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}
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// Replace a use of the cmp with a use of the new cmp.
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TheUse = InsertedCmp;
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}
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// If we removed all uses, nuke the cmp.
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if (CI->use_empty())
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CI->eraseFromParent();
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return MadeChange;
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}
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/// EraseDeadInstructions - Erase any dead instructions
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static void EraseDeadInstructions(Value *V) {
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Instruction *I = dyn_cast<Instruction>(V);
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@ -894,6 +950,8 @@ bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
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if (TLI)
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MadeChange |= OptimizeNoopCopyExpression(CI, *TLI);
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} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
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MadeChange |= OptimizeCmpExpression(CI);
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} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
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if (TLI)
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MadeChange |= OptimizeLoadStoreInst(I, I->getOperand(0), LI->getType(),
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