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NewGVN: Only call isInstructionTrivially dead once per instruction. 

llvm-svn: 297046
This commit is contained in:
Daniel Berlin 2017-03-06 18:42:27 +00:00
parent 812191584f
commit 856fa14e06
1 changed files with 10 additions and 9 deletions
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19
llvm/lib/Transforms/Scalar/NewGVN.cpp
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@ -1730,6 +1730,16 @@ std::pair<unsigned, unsigned> NewGVN::assignDFSNumbers(BasicBlock *B,
}
for (auto &I : *B) {
// There's no need to call isInstructionTriviallyDead more than once on
// an instruction. Therefore, once we know that an instruction is dead
// we change its DFS number so that it doesn't get value numbered.
if (isInstructionTriviallyDead(&I, TLI)) {
InstrDFS[&I] = 0;
DEBUG(dbgs() << "Skipping trivially dead instruction " << I << "\n");
markInstructionForDeletion(&I);
continue;
}
InstrDFS[&I] = End++;
DFSToInstr.emplace_back(&I);
}
@ -1800,15 +1810,6 @@ void NewGVN::valueNumberMemoryPhi(MemoryPhi *MP) {
// congruence finding, and updating mappings.
void NewGVN::valueNumberInstruction(Instruction *I) {
DEBUG(dbgs() << "Processing instruction " << *I << "\n");
// There's no need to call isInstructionTriviallyDead more than once on
// an instruction. Therefore, once we know that an instruction is dead
// we change its DFS number so that it doesn't get numbered again.
if (InstrDFS[I] != 0 && isInstructionTriviallyDead(I, TLI)) {
InstrDFS[I] = 0;
DEBUG(dbgs() << "Skipping unused instruction\n");
markInstructionForDeletion(I);
return;
}
if (!I->isTerminator()) {
const Expression *Symbolized = nullptr;
if (DebugCounter::shouldExecute(VNCounter)) {