Revert "[SimplifyCFG] Check if the return instruction causes undefine…

…d behavior" This reverts commit b6a0be8.
llvm · Mar 19, 2023 · 6505b9d · 6505b9d
1 parent c6e54c7
commit 6505b9d
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diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -7115,20 +7115,6 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValu
         return passingValueIsAlwaysUndefined(V, GEP, PtrValueMayBeModified);
       }
 
-    // Look through return.
-    if (ReturnInst *Ret = dyn_cast<ReturnInst>(Use)) {
-      bool HasNoUndefAttr =
-          Ret->getFunction()->hasRetAttribute(Attribute::NoUndef);
-      // Return undefined to a noundef return value is undefined.
-      if (isa<UndefValue>(C) && HasNoUndefAttr)
-        return true;
-      // Return null to a nonnull+noundef return value is undefined.
-      if (C->isNullValue() && HasNoUndefAttr &&
-          Ret->getFunction()->hasRetAttribute(Attribute::NonNull)) {
-        return !PtrValueMayBeModified;
-      }
-    }
-
     // Look through bitcasts.
     if (BitCastInst *BC = dyn_cast<BitCastInst>(Use))
       return passingValueIsAlwaysUndefined(V, BC, PtrValueMayBeModified);

diff --git a/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll b/llvm/test/Transforms/SimplifyCFG/unreachable-eliminate-on-ret.ll