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Fix some nondeterminstic behavior in the mem2reg pass that (in addition to

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nondeterminism being bad) could cause some trivial missed optimizations (dead
phi nodes being left around for later passes to clean up).

With this, llvm-gcc4 now bootstraps and correctly compares.  I don't know
why I never tried to do it before... :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27984 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-04-27 01:14:43 +00:00
parent 7b8229a146
commit 634c76c08c
1 changed files with 38 additions and 20 deletions
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58
lib/Transforms/Utils/PromoteMemoryToRegister.cpp
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@ -147,7 +147,7 @@ void PromoteMem2Reg::run() {
if (AI->use_empty()) {
// If there are no uses of the alloca, just delete it now.
if (AST) AST->deleteValue(AI);
AI->getParent()->getInstList().erase(AI);
AI->eraseFromParent();
// Remove the alloca from the Allocas list, since it has been processed
Allocas[AllocaNum] = Allocas.back();
@ -331,7 +331,7 @@ void PromoteMem2Reg::run() {
if (AST && isa<PointerType>(PN->getType()))
AST->deleteValue(PN);
PN->getParent()->getInstList().erase(PN);
PN->eraseFromParent();
}
// Keep the reverse mapping of the 'Allocas' array.
@ -377,7 +377,7 @@ void PromoteMem2Reg::run() {
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
Visited.clear();
// Remove the allocas themselves from the function...
// Remove the allocas themselves from the function.
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
Instruction *A = Allocas[i];
@ -388,9 +388,41 @@ void PromoteMem2Reg::run() {
if (!A->use_empty())
A->replaceAllUsesWith(UndefValue::get(A->getType()));
if (AST) AST->deleteValue(A);
A->getParent()->getInstList().erase(A);
A->eraseFromParent();
}
// Loop over all of the PHI nodes and see if there are any that we can get
// rid of because they merge all of the same incoming values. This can
// happen due to undef values coming into the PHI nodes. This process is
// iterative, because eliminating one PHI node can cause others to be removed.
bool EliminatedAPHI = true;
while (EliminatedAPHI) {
EliminatedAPHI = false;
for (std::map<BasicBlock*, std::vector<PHINode *> >::iterator I =
NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) {
std::vector<PHINode*> &PNs = I->second;
for (unsigned i = 0, e = PNs.size(); i != e; ++i) {
if (!PNs[i]) continue;
// If this PHI node merges one value and/or undefs, get the value.
if (Value *V = PNs[i]->hasConstantValue(true)) {
if (!isa<Instruction>(V) ||
properlyDominates(cast<Instruction>(V), PNs[i])) {
if (AST && isa<PointerType>(PNs[i]->getType()))
AST->deleteValue(PNs[i]);
PNs[i]->replaceAllUsesWith(V);
PNs[i]->eraseFromParent();
PNs[i] = 0;
EliminatedAPHI = true;
continue;
}
}
}
}
}
// At this point, the renamer has added entries to PHI nodes for all reachable
// code. Unfortunately, there may be blocks which are not reachable, which
// the renamer hasn't traversed. If this is the case, the PHI nodes may not
@ -403,25 +435,11 @@ void PromoteMem2Reg::run() {
std::vector<BasicBlock*> Preds(pred_begin(I->first), pred_end(I->first));
std::vector<PHINode*> &PNs = I->second;
assert(!PNs.empty() && "Empty PHI node list??");
// Loop over all of the PHI nodes and see if there are any that we can get
// rid of because they merge all of the same incoming values. This can
// happen due to undef values coming into the PHI nodes.
PHINode *SomePHI = 0;
for (unsigned i = 0, e = PNs.size(); i != e; ++i)
if (PNs[i]) {
if (Value *V = PNs[i]->hasConstantValue(true)) {
if (!isa<Instruction>(V) ||
properlyDominates(cast<Instruction>(V), PNs[i])) {
if (AST && isa<PointerType>(PNs[i]->getType()))
AST->deleteValue(PNs[i]);
PNs[i]->replaceAllUsesWith(V);
PNs[i]->eraseFromParent();
PNs[i] = 0;
}
}
if (PNs[i])
SomePHI = PNs[i];
SomePHI = PNs[i];
break;
}
// Only do work here if there the PHI nodes are missing incoming values. We