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De-pessimize the handling of LCSSA Phi nodes in IndVarSimplify. Hopefully this

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will make Shootout-C/nestedloop faster.

llvm-svn: 28924
This commit is contained in:
Owen Anderson 2006-06-27 02:17:08 +00:00
parent 10e71f60df
commit 1c3b04d485
1 changed files with 29 additions and 15 deletions
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44
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -325,20 +325,8 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (!L->contains(User->getParent())) {
// If this is a PHI node in the exit block and we're inserting,
// into the exit block, it must have a single entry. In this
// case, we can't insert the code after the PHI and have the PHI
// still use it. Instead, don't insert the the PHI.
if (PHINode *PN = dyn_cast<PHINode>(User)) {
// FIXME: This is a case where LCSSA pessimizes code, this
// should be fixed better.
if (PN->getNumOperands() == 2 &&
PN->getParent() == BlockToInsertInto)
continue;
}
if (!L->contains(User->getParent()))
ExtraLoopUsers.push_back(User);
}
}
if (!ExtraLoopUsers.empty()) {
@ -358,8 +346,34 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
// Rewrite any users of the computed value outside of the loop
// with the newly computed value.
for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i)
ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal);
for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) {
PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]);
if (PN && PN->getParent() == BlockToInsertInto) {
// We're dealing with an LCSSA Phi. Handle it specially.
Instruction* LCSSAInsertPt = BlockToInsertInto->begin();
Instruction* NewInstr = dyn_cast<Instruction>(NewVal);
if (Instruction* NewInstr = dyn_cast<Instruction>(NewVal))
for (unsigned j = 0; j < NewInstr->getNumOperands(); ++j){
Instruction* PredI =
dyn_cast<Instruction>(NewInstr->getOperand(j));
if (PredI && L->contains(PredI->getParent())) {
PHINode* NewLCSSA = new PHINode(PredI->getType(),
PredI->getName() + ".lcssa",
LCSSAInsertPt);
NewLCSSA->addIncoming(PredI,
BlockToInsertInto->getSinglePredecessor());
NewInstr->replaceUsesOfWith(PredI, NewLCSSA);
}
}
PN->replaceAllUsesWith(NewVal);
PN->eraseFromParent();
} else {
ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal);
}
}
// If this instruction is dead now, schedule it to be removed.
if (I->use_empty())