[PATCH] D129874: [SCEV][NFC][CT] Cheaper handling of guards in isBasicBlockEntryGuardedByCond

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.
mkazantsev added reviewers: skatkov, reames, lebedev.ri, nikic.
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Handle guards uniformly with assumes, rather than iterating through all
block instructions in attempt to find them.


https://reviews.llvm.org/D129874

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp


Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -11154,20 +11154,6 @@
       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();
@@ -11194,9 +11180,6 @@
     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())
@@ -11219,6 +11202,16 @@
       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;
 }
 


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