[llvm] [InstCombine] Fold shuffled intrinsic operands with constant operands (PR #141300)

[Nikita Popov via llvm-commits]

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@@ -802,6 +802,67 @@ define <2 x float> @fma_unary_shuffle_ops_narrowing(<3 x float> %x, <3 x float>
   ret <2 x float> %r
 }
 
+define <2 x float> @fma_unary_shuffle_ops_1_const(<2 x float> %x, <2 x float> %y) {
+; CHECK-LABEL: @fma_unary_shuffle_ops_1_const(
+; CHECK-NEXT:    [[Y:%.*]] = call <2 x float> @llvm.fma.v2f32(<2 x float> [[X:%.*]], <2 x float> <float 2.000000e+00, float 1.000000e+00>, <2 x float> [[Y1:%.*]])
+; CHECK-NEXT:    [[B:%.*]] = shufflevector <2 x float> [[Y]], <2 x float> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    ret <2 x float> [[B]]
+;
+  %a = shufflevector <2 x float> %x, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %b = shufflevector <2 x float> %y, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %r = call <2 x float> @llvm.fma(<2 x float> <float 1.0, float 2.0>, <2 x float> %a, <2 x float> %b)
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nikic wrote:

FWIW, I found these tests a bit confusing because the order of arguments changed. It would be more obvious to put the constants in the second arg in the first place, rather than have InstCombine canonicalize them first.

https://github.com/llvm/llvm-project/pull/141300