[PATCH] D55787: [X86] Use UADDSAT/USUBSAT instead of ADDUS/SUBUS

Mon Dec 17 16:26:43 PST 2018

craig.topper added inline comments.

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Comment at: test/CodeGen/X86/uadd_sat_vec.ll:614
+;
+; AVX512-LABEL: v16i1:
+; AVX512:       # %bb.0:
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nikic wrote:
> This expansion is pretty crazy...
Yeah I wouldn't expect vXi1 to be good, but this is even worse than I imagined. Its definitely being scalarized and then promoted. But the scalarization looks weird. But I'm not sure how much we care.

We can pretty easily replace with vXi1 ADDUSAT with OR X,Y and SUBUSAT with X & ~Y if we care.

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Comment at: test/CodeGen/X86/uadd_sat_vec.ll:619
+; AVX512-NEXT:    pushq %r15
+; AVX512-NEXT:    .cfi_def_cfa_offset 24
+; AVX512-NEXT:    pushq %r14
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Can you add nounwind to the test case to drop the .cfi directives

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55787/new/

https://reviews.llvm.org/D55787