[llvm] Reland `[CodeGenPrepare] Convert `ctpop(X) ==/!= 1` into `ctpop(X) u</u> 2/1` (#111284)` (PR #111998)

[via llvm-commits]

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@@ -155,7 +155,7 @@ define <4 x i1> @neither_pow2_non_zero_4xv64(<4 x i64> %xin) {
 ; CHECK-AVX512:       # %bb.0:
 ; CHECK-AVX512-NEXT:    vporq {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to4}, %ymm0, %ymm0
 ; CHECK-AVX512-NEXT:    vpopcntq %ymm0, %ymm0
-; CHECK-AVX512-NEXT:    vpcmpneqq {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to4}, %ymm0, %k1
+; CHECK-AVX512-NEXT:    vpcmpgtq {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to4}, %ymm0, %k1
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goldsteinn wrote:

noticing, this is probably not profitable for vectors on x86-64. Particularly if there is no avx512

https://github.com/llvm/llvm-project/pull/111998