[llvm] 1383cb6 - [ConstFold] Fix incorrect gep inbounds of undef fold

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2024-05-28T11:14:07+02:00
New Revision: 1383cb6e648ba9f4516fa2317f948116c4f35c10

URL: https://github.com/llvm/llvm-project/commit/1383cb6e648ba9f4516fa2317f948116c4f35c10
DIFF: https://github.com/llvm/llvm-project/commit/1383cb6e648ba9f4516fa2317f948116c4f35c10.diff

LOG: [ConstFold] Fix incorrect gep inbounds of undef fold

gep inbounds of undef can only be folded to poison if we know
that the offset is non-zero. I don't think precise handling here
is important, so just drop the inbounds special case. This matches
what InstSimplify does.

Added: 
    

Modified: 
    llvm/lib/IR/ConstantFold.cpp
    llvm/test/Transforms/InstSimplify/ConstProp/poison.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index 4c5e1ce3df7c7..8fce782f47a9c 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -1549,8 +1549,7 @@ Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
     return PoisonValue::get(GEPTy);
 
   if (isa<UndefValue>(C))
-    // If inbounds, we can choose an out-of-bounds pointer as a base pointer.
-    return InBounds ? PoisonValue::get(GEPTy) : UndefValue::get(GEPTy);
+    return UndefValue::get(GEPTy);
 
   auto IsNoOp = [&]() {
     // Avoid losing inrange information.

diff  --git a/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll b/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
index cc498abd9af0f..8fbe5323742df 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
@@ -104,7 +104,7 @@ define void @vec_aggr_ops() {
 
 define void @other_ops(i8 %x) {
 ; CHECK-LABEL: @other_ops(
-; CHECK-NEXT:    call void (...) @use(i1 poison, i1 poison, i8 poison, i8 poison, ptr poison, ptr poison, ptr poison)
+; CHECK-NEXT:    call void (...) @use(i1 poison, i1 poison, i8 poison, i8 poison, ptr poison, ptr undef, ptr undef)
 ; CHECK-NEXT:    ret void
 ;
   %i1 = icmp eq i8 poison, 1