[llvm] [WIP][X86] lowerBuildVectorAsBroadcast - don't convert constant vectors to broadcasts on AVX512VL targets (PR #73509)

[Simon Pilgrim via llvm-commits]

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@@ -384,7 +376,7 @@ declare <8 x half> @llvm.fabs.v8f16(<8 x half>)
 define <8 x half> @fcopysignv8f16(<8 x half> %x, <8 x half> %y) {
 ; CHECK-LABEL: fcopysignv8f16:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    vpternlogq $228, {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to2}, %xmm1, %xmm0
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RKSimon wrote:

Looks like canonicalizeBitSelect tends to default to vpternlogq instead of vpternlogd for small types - I'll look at a fix.

https://github.com/llvm/llvm-project/pull/73509