[llvm] [WebAssembly] Fold extended vector shifts by constant to extmul (PR #184007)

[Sam Parker via llvm-commits]

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@@ -195,3 +195,47 @@ define <8 x i32> @zext_sext_mul_v8i16(<8 x i16> %a, <8 x i16> %b) {
   %mul = mul <8 x i32> %wide.a, %wide.b
   ret <8 x i32> %mul
 }
+
+define <4 x i32> @sext_mul_v8i16_with_symmetric_constant_vector(<8 x i16> %v) {
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sparker-arm wrote:

So what's the type of the constant vector you're creating? It looks like legalization is breaking it up, but it's confusing me as to why. Can we change the element type to try to ensure it's`<8 x i16>`?

https://github.com/llvm/llvm-project/pull/184007