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[SCEV][NFC][CT] Cheaper handling of guards in isBasicBlockEntryGuardedByCond 

Handle guards uniformly with assumes, rather than iterating through all
block instructions in attempt to find them.

Differential Revision: https://reviews.llvm.org/D129874
Reviewed By: nikic
This commit is contained in:
Max Kazantsev 2022-07-25 11:56:01 +07:00
parent 9d5a544d34
commit a053f35990
1 changed files with 9 additions and 17 deletions
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26
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -11153,20 +11153,6 @@ bool ScalarEvolution::isBasicBlockEntryGuardedByCond(const BasicBlock *BB,
return true;
}
// Try to prove (Pred, LHS, RHS) using isImpliedViaGuard.
auto ProveViaGuard = [&](const BasicBlock *Block) {
if (isImpliedViaGuard(Block, Pred, LHS, RHS))
return true;
if (ProvingStrictComparison) {
auto ProofFn = [&](ICmpInst::Predicate P) {
return isImpliedViaGuard(Block, P, LHS, RHS);
};
if (SplitAndProve(ProofFn))
return true;
}
return false;
};
// Try to prove (Pred, LHS, RHS) using isImpliedCond.
auto ProveViaCond = [&](const Value *Condition, bool Inverse) {
const Instruction *CtxI = &BB->front();
@ -11193,9 +11179,6 @@ bool ScalarEvolution::isBasicBlockEntryGuardedByCond(const BasicBlock *BB,
PredBB = BB->getSinglePredecessor();
for (std::pair<const BasicBlock *, const BasicBlock *> Pair(PredBB, BB);
Pair.first; Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
if (ProveViaGuard(Pair.first))
return true;
const BranchInst *BlockEntryPredicate =
dyn_cast<BranchInst>(Pair.first->getTerminator());
if (!BlockEntryPredicate || BlockEntryPredicate->isUnconditional())
@ -11218,6 +11201,15 @@ bool ScalarEvolution::isBasicBlockEntryGuardedByCond(const BasicBlock *BB,
return true;
}
// Check conditions due to any @llvm.experimental.guard intrinsics.
auto *GuardDecl = F.getParent()->getFunction(
Intrinsic::getName(Intrinsic::experimental_guard));
if (GuardDecl)
for (const auto *GU : GuardDecl->users())
if (const auto *Guard = dyn_cast<IntrinsicInst>(GU))
if (Guard->getFunction() == BB->getParent() && DT.dominates(Guard, BB))
if (ProveViaCond(Guard->getArgOperand(0), false))
return true;
return false;
}