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Sink CmpInst's to their uses to reduce register pressure.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37554 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2007-06-12 16:50:17 +00:00
parent 9c7ee6b19f
commit ce0b23721e
1 changed files with 61 additions and 3 deletions
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64
lib/Transforms/Scalar/CodeGenPrepare.cpp
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@ -317,7 +317,7 @@ static void SplitEdgeNicely(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
/// copy (e.g. it's casting from one pointer type to another, int->uint, or
/// int->sbyte on PPC), sink it into user blocks to reduce the number of virtual
/// registers that must be created and coallesced.
/// registers that must be created and coalesced.
///
/// Return true if any changes are made.
static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
@ -348,7 +348,7 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
BasicBlock *DefBB = CI->getParent();
/// InsertedCasts - Only insert a cast in each block once.
std::map<BasicBlock*, CastInst*> InsertedCasts;
DenseMap<BasicBlock*, CastInst*> InsertedCasts;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
@ -383,7 +383,7 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
MadeChange = true;
}
// Replace a use of the cast with a use of the new casat.
// Replace a use of the cast with a use of the new cast.
TheUse = InsertedCast;
}
@ -394,6 +394,62 @@ static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI){
return MadeChange;
}
/// OptimizeCmpExpression - sink the given CmpInst into user blocks to reduce
/// the number of virtual registers that must be created and coalesced. This is
/// a clear win except on targets with multiple condition code registers (powerPC),
/// where it might lose; some adjustment may be wanted there.
///
/// Return true if any changes are made.
static bool OptimizeCmpExpression(CmpInst *CI){
BasicBlock *DefBB = CI->getParent();
/// InsertedCmp - Only insert a cmp in each block once.
DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Preincrement use iterator so we don't invalidate it.
++UI;
// Don't bother for PHI nodes.
if (isa<PHINode>(User))
continue;
// Figure out which BB this cmp is used in.
BasicBlock *UserBB = User->getParent();
// If this user is in the same block as the cmp, don't change the cmp.
if (UserBB == DefBB) continue;
// If we have already inserted a cmp into this block, use it.
CmpInst *&InsertedCmp = InsertedCmps[UserBB];
if (!InsertedCmp) {
BasicBlock::iterator InsertPt = UserBB->begin();
while (isa<PHINode>(InsertPt)) ++InsertPt;
InsertedCmp =
CmpInst::create(CI->getOpcode(), CI->getPredicate(), CI->getOperand(0),
CI->getOperand(1), "", InsertPt);
MadeChange = true;
}
// Replace a use of the cmp with a use of the new cmp.
TheUse = InsertedCmp;
}
// If we removed all uses, nuke the cmp.
if (CI->use_empty())
CI->eraseFromParent();
return MadeChange;
}
/// EraseDeadInstructions - Erase any dead instructions
static void EraseDeadInstructions(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
@ -894,6 +950,8 @@ bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
if (TLI)
MadeChange |= OptimizeNoopCopyExpression(CI, *TLI);
} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
MadeChange |= OptimizeCmpExpression(CI);
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (TLI)
MadeChange |= OptimizeLoadStoreInst(I, I->getOperand(0), LI->getType(),