[llvm] a053f35 - [SCEV][NFC][CT] Cheaper handling of guards in isBasicBlockEntryGuardedByCond

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2022-07-25T13:38:59+07:00
New Revision: a053f359908b3645e54f820b551110764f964c66

URL: https://github.com/llvm/llvm-project/commit/a053f359908b3645e54f820b551110764f964c66
DIFF: https://github.com/llvm/llvm-project/commit/a053f359908b3645e54f820b551110764f964c66.diff

LOG: [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

Added: 
    

Modified: 
    llvm/lib/Analysis/ScalarEvolution.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index d46248aa3889..2958a5054afc 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -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;
 }