[PATCH] D13505: [X86] Fix bad treatment of multi-lane blends in BUILD_VECTORtoBlendMask()

[Filipe Cabecinhas via llvm-commits]

filcab added a comment.

I have a question:
This looks like it's to generate BLENDI nodes, in order to match the Intel instructions for blends with immediates...
But there are no byte-shuffles with immediates, AFAICT.

What did I miss?

P.S: If I change that function to bail out on ElemType == MVT::i8, I see the masks reversed (but both lanes are equal)...


================
Comment at: test/CodeGen/X86/vector-blend.ll:664
@@ +663,3 @@
+; AVX1-NEXT:    vextractf128    $1, %ymm0, %xmm3
+; AVX1-NEXT:    vmovdqa .LCPI18_0(%rip), %xmm4  # xmm4 = [255,255,0,255,0,0,0,255,255,255,0,255,0,0,0,255]
+; AVX1-NEXT:    vpblendvb       %xmm4, %xmm2, %xmm3, %xmm2
----------------
Why are the "first lanes" changing here? Either it was completely wrong, and you're fixing it, or the replacement is wrong (the "second lane" was always wrong).


http://reviews.llvm.org/D13505