[InstSimplify] Fold (insertelement Splat(C), C, X) -> Splat(C) (llvm#…

…102315) The index doesn't matter here.
ROCm · Aug 7, 2024 · c31ac81 · c31ac81
1 parent 06a808c
commit c31ac81
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diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5181,6 +5181,10 @@ Value *llvm::simplifyInsertElementInst(Value *Vec, Value *Val, Value *Idx,
  (Q.isUndefValue(Val) && isGuaranteedNotToBePoison(Vec)))
  return Vec;
 
+ // Inserting the splatted value into a constant splat does nothing.
+ if (VecC && ValC && VecC->getSplatValue() == ValC)
+ return Vec;
+
  // If we are extracting a value from a vector, then inserting it into the same
  // place, that's the input vector:
  // insertelt Vec, (extractelt Vec, Idx), Idx --> Vec

diff --git a/llvm/test/Transforms/InstSimplify/insertelement.ll b/llvm/test/Transforms/InstSimplify/insertelement.ll
@@ -119,3 +119,11 @@ unreachable_infloop:
  %bogus = insertelement <2 x i64> %bogus, i64 undef, i32 1
  br label %unreachable_infloop
 }
+
+define <4 x i32> @insert_into_splat(i32 %index) {
+; CHECK-LABEL: @insert_into_splat(
+; CHECK-NEXT: ret <4 x i32> <i32 3, i32 3, i32 3, i32 3>
+;
+ %I = insertelement <4 x i32> <i32 3, i32 3, i32 3, i32 3>, i32 3, i32 %index
+ ret <4 x i32> %I
+}