[PATCH] D149935: [ValueTracking] Imply poison if ValAssumePoison is identical to V

[luxufan via Phabricator via llvm-commits]

StephenFan created this revision.
StephenFan added reviewers: nikic, goldstein.w.n.
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StephenFan requested review of this revision.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149935

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/InstCombine/signed-truncation-check.ll


Index: llvm/test/Transforms/InstCombine/signed-truncation-check.ll
===================================================================
--- llvm/test/Transforms/InstCombine/signed-truncation-check.ll
+++ llvm/test/Transforms/InstCombine/signed-truncation-check.ll
@@ -661,7 +661,7 @@
 ; CHECK-NEXT:    call void @use32(i32 [[T4]])
 ; CHECK-NEXT:    [[T5:%.*]] = icmp eq i32 [[T4]], [[ARG]]
 ; CHECK-NEXT:    call void @use1(i1 [[T5]])
-; CHECK-NEXT:    [[T6:%.*]] = select i1 [[T2]], i1 [[T5]], i1 false
+; CHECK-NEXT:    [[T6:%.*]] = and i1 [[T2]], [[T5]]
 ; CHECK-NEXT:    ret i1 [[T6]]
 ;
   %t1 = trunc i32 %arg to i8
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -6509,6 +6509,11 @@
   if (ValAssumedPoison == V)
     return true;
 
+  auto *IAssumedPoison = dyn_cast<Instruction>(ValAssumedPoison);
+  auto *IV = dyn_cast<Instruction>(V);
+  if (IAssumedPoison && IV && IAssumedPoison->isIdenticalTo(IV))
+    return true;
+
   const unsigned MaxDepth = 2;
   if (Depth >= MaxDepth)
     return false;


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