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Remove dead code in GVN: now that SimplifyInstruction is called

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systematically, CollapsePhi will always return null here.  Note
that CollapsePhi did an extra check, isSafeReplacement, which
the SimplifyInstruction logic does not do.  I think that check
was bogus - I guess we will soon find out!  (It was originally
added in commit 41998 without a testcase).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119456 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-11-17 04:05:21 +00:00
parent 6678e7b6eb
commit d32c4a1756
1 changed files with 2 additions and 43 deletions
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45
lib/Transforms/Scalar/GVN.cpp
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@ -701,7 +701,6 @@ namespace {
bool processBlock(BasicBlock *BB);
void dump(DenseMap<uint32_t, Value*>& d);
bool iterateOnFunction(Function &F);
Value *CollapsePhi(PHINode* p);
bool performPRE(Function& F);
Value *lookupNumber(BasicBlock *BB, uint32_t num);
void cleanupGlobalSets();
@ -733,33 +732,6 @@ void GVN::dump(DenseMap<uint32_t, Value*>& d) {
errs() << "}\n";
}
static bool isSafeReplacement(PHINode* p, Instruction *inst) {
if (!isa<PHINode>(inst))
return true;
for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end();
UI != E; ++UI)
if (PHINode* use_phi = dyn_cast<PHINode>(*UI))
if (use_phi->getParent() == inst->getParent())
return false;
return true;
}
Value *GVN::CollapsePhi(PHINode *PN) {
Value *ConstVal = PN->hasConstantValue(DT);
if (!ConstVal) return 0;
Instruction *Inst = dyn_cast<Instruction>(ConstVal);
if (!Inst)
return ConstVal;
if (DT->dominates(Inst, PN))
if (isSafeReplacement(PN, Inst))
return Inst;
return 0;
}
/// IsValueFullyAvailableInBlock - Return true if we can prove that the value
/// we're analyzing is fully available in the specified block. As we go, keep
/// track of which blocks we know are fully alive in FullyAvailableBlocks. This
@ -1954,21 +1926,8 @@ bool GVN::processInstruction(Instruction *I,
return false;
}
// Collapse PHI nodes
if (PHINode* p = dyn_cast<PHINode>(I)) {
Value *constVal = CollapsePhi(p);
if (constVal) {
p->replaceAllUsesWith(constVal);
if (MD && constVal->getType()->isPointerTy())
MD->invalidateCachedPointerInfo(constVal);
VN.erase(p);
toErase.push_back(p);
} else {
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
}
if (isa<PHINode>(I)) {
localAvail[I->getParent()]->table.insert(std::make_pair(Num, I));
// If the number we were assigned was a brand new VN, then we don't
// need to do a lookup to see if the number already exists
// somewhere in the domtree: it can't!