[PATCH] D14901: [X86][SSE] Improve i16 splatting shuffles

Quentin Colombet via llvm-commits llvm-commits at lists.llvm.org
Wed Dec 16 10:44:36 PST 2015

qcolombet added inline comments.

Comment at: test/CodeGen/X86/avx-splat.ll:18
@@ -18,1 +17,3 @@
+; CHECK-NEXT:    vpshufhw {{.*#+}} xmm0 = xmm0[0,1,2,3,5,5,5,5]
+; CHECK-NEXT:    vpshufd {{.*#+}} xmm0 = xmm0[2,2,3,3]
 ; CHECK-NEXT:    vinsertf128 $1, %xmm0, %ymm0, %ymm0
I am missing something.

You said:
> Note this has the side effect of a lot of SSSE3 test cases no longer needing to use PSHUFB, as it falls below the 3 op combine threshold for when PSHUFB is typically worth it.

But isn’t pshufb always better than two other pshufX instructions?



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