[llvm] [VPlan] Consolidate logic for narrow to single scalars (PR #151506)

[Ramkumar Ramachandra via llvm-commits]

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@@ -57,11 +57,11 @@ define void @ld_div2_step1_start0_ind1(ptr noalias %A, ptr noalias %B) {
 ; CHECK-NEXT:    [[TMP0:%.*]] = udiv i64 [[INDEX]], 2
 ; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 [[TMP0]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = load i64, ptr [[TMP1]], align 8
-; CHECK-NEXT:    [[TMP3:%.*]] = add nsw i64 [[TMP2]], 42
-; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[TMP3]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <2 x i64> poison, i64 [[TMP2]], i64 0
 ; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <2 x i64> [[BROADCAST_SPLATINSERT]], <2 x i64> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = add nsw <2 x i64> [[BROADCAST_SPLAT]], splat (i64 42)
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artagnon wrote:

I tried my best to squash the regression in a principled manner, but the best I was able to do was to put in a hacky exception: the hack has resulted in some unrelated improvements.

https://github.com/llvm/llvm-project/pull/151506