[PATCH] D92203: [ConstantFold] Fold operations to poison if possible

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added inline comments.


================
Comment at: llvm/lib/IR/ConstantFold.cpp:784
+  if (isa<PoisonValue>(Cond))
+    return PoisonValue::get(V1->getType());
+
----------------
This is poison because `select poison, ?, ?` is poison.


================
Comment at: llvm/lib/IR/ConstantFold.cpp:841
+  // extractelt poison, C -> poison
+  // extractelt C, undef -> poison
+  if (isa<PoisonValue>(Val) || isa<UndefValue>(Idx))
----------------
This is poison because undef can be folded into out-of-bounds index, which makes extractelement yield poison according to LangRef.


================
Comment at: llvm/lib/IR/ConstantFold.cpp:905
   if (isa<UndefValue>(Idx))
-    return UndefValue::get(Val->getType());
+    return PoisonValue::get(Val->getType());
 
----------------
This is poison because insertelement with out-of-bounds index yields poison.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D92203/new/

https://reviews.llvm.org/D92203