[llvm] [Scalarizer] Use correct key for ExtractValueInst gather (PR #149855)

[Deric C. via llvm-commits]

https://github.com/Icohedron created https://github.com/llvm/llvm-project/pull/149855

Fixes #149345

Effectively no-op pairs of insertelement-extractelement instructions were being created due to the ExtractValueInst visitor in the Scalarizer storing its scalarized result into the Scattered map using an incorrect key (specifically the type used in the key). 
This PR fixes this issue.

>From b340f9392ddf106ea5dde4ed4e76f4b6390cf582 Mon Sep 17 00:00:00 2001
From: Deric Cheung <dericcheung at microsoft.com>
Date: Mon, 21 Jul 2025 16:51:25 +0000
Subject: [PATCH] Use correct key for ExtractValueInst gather

---
 llvm/lib/Transforms/Scalar/Scalarizer.cpp | 4 +++-
 llvm/test/CodeGen/DirectX/UAddc.ll        | 8 ++------
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/Scalarizer.cpp b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
index 820c8e12d2449..ced61cb8e51fe 100644
--- a/llvm/lib/Transforms/Scalar/Scalarizer.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
@@ -1105,7 +1105,9 @@ bool ScalarizerVisitor::visitExtractValueInst(ExtractValueInst &EVI) {
     Res.push_back(ResElem);
   }
 
-  gather(&EVI, Res, *VS);
+  Type *ActualVecType = cast<FixedVectorType>(OpTy->getContainedType(Index));
+  std::optional<VectorSplit> AVS = getVectorSplit(ActualVecType);
+  gather(&EVI, Res, *AVS);
   return true;
 }
 
diff --git a/llvm/test/CodeGen/DirectX/UAddc.ll b/llvm/test/CodeGen/DirectX/UAddc.ll
index 4b46b56b455f6..dd7aa23122c84 100644
--- a/llvm/test/CodeGen/DirectX/UAddc.ll
+++ b/llvm/test/CodeGen/DirectX/UAddc.ll
@@ -35,14 +35,10 @@ define noundef <2 x i32> @test_UAddc_vec2(<2 x i32> noundef %a, <2 x i32> nounde
 ; CHECK-NEXT:    [[UADDC_I1:%.*]] = call [[DX_TYPES_I32C]] @dx.op.binaryWithCarryOrBorrow.i32(i32 44, i32 [[A_I1]], i32 [[B_I1]]) #[[ATTR0]]
 ; CHECK-NEXT:    [[CARRY_ELEM0:%.*]] = extractvalue [[DX_TYPES_I32C]] [[UADDC_I0]], 1
 ; CHECK-NEXT:    [[CARRY_ELEM1:%.*]] = extractvalue [[DX_TYPES_I32C]] [[UADDC_I1]], 1
-; CHECK-NEXT:    [[CARRY_UPTO0:%.*]] = insertelement <2 x i1> poison, i1 [[CARRY_ELEM0]], i64 0
-; CHECK-NEXT:    [[CARRY:%.*]] = insertelement <2 x i1> [[CARRY_UPTO0]], i1 [[CARRY_ELEM1]], i64 1
-; CHECK-NEXT:    [[CARRY_I0:%.*]] = extractelement <2 x i1> [[CARRY]], i64 0
-; CHECK-NEXT:    [[CARRY_I1:%.*]] = extractelement <2 x i1> [[CARRY]], i64 1
 ; CHECK-NEXT:    [[SUM_ELEM0:%.*]] = extractvalue [[DX_TYPES_I32C]] [[UADDC_I0]], 0
 ; CHECK-NEXT:    [[SUM_ELEM1:%.*]] = extractvalue [[DX_TYPES_I32C]] [[UADDC_I1]], 0
-; CHECK-NEXT:    [[CARRY_ZEXT_I0:%.*]] = zext i1 [[CARRY_I0]] to i32
-; CHECK-NEXT:    [[CARRY_ZEXT_I1:%.*]] = zext i1 [[CARRY_I1]] to i32
+; CHECK-NEXT:    [[CARRY_ZEXT_I0:%.*]] = zext i1 [[CARRY_ELEM0]] to i32
+; CHECK-NEXT:    [[CARRY_ZEXT_I1:%.*]] = zext i1 [[CARRY_ELEM1]] to i32
 ; CHECK-NEXT:    [[RESULT_I0:%.*]] = add i32 [[SUM_ELEM0]], [[CARRY_ZEXT_I0]]
 ; CHECK-NEXT:    [[RESULT_I1:%.*]] = add i32 [[SUM_ELEM1]], [[CARRY_ZEXT_I1]]
 ; CHECK-NEXT:    [[RESULT_UPTO0:%.*]] = insertelement <2 x i32> poison, i32 [[RESULT_I0]], i64 0