[PATCH] D18850: [X86]: Fix for PR27251

[Smith, Kevin B via llvm-commits]

>-----Original Message-----
>From: David Kreitzer [mailto:david.l.kreitzer at intel.com]
>Sent: Thursday, April 07, 2016 8:22 AM
>To: Smith, Kevin B <kevin.b.smith at intel.com>;
>ahmed.bougacha at gmail.com; Kreitzer, David L <david.l.kreitzer at intel.com>
>Cc: llvm-commits at lists.llvm.org
>Subject: Re: [PATCH] D18850: [X86]: Fix for PR27251
>
>DavidKreitzer added a comment.
>
>LGTM, Kevin.
>
>
>================
>Comment at: test/CodeGen/X86/vector-blend.ll:1011
>@@ -1010,3 +1010,3 @@
> ; SSE2-NEXT:    pslld $31, %xmm1
> ; SSE2-NEXT:    psrad $31, %xmm1
> ; SSE2-NEXT:    pxor %xmm1, %xmm0
>----------------
>I know this isn't related to your change, but the redundant shifts here are
>pretty gross.

Why are the shifts redundant?  One is a shift left by 31, and the other is a arithmetic shift right by 31.
This has the effect of propagating bit 0 through all 32 bits of the vector element.

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>http://reviews.llvm.org/D18850
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