[llvm-bugs] [Bug 36761] New: [X86] Missed opportunities to use vcvtdq2pd %xmm0, %xmm0 under AVX

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36761

            Bug ID: 36761
           Summary: [X86] Missed opportunities to use vcvtdq2pd %xmm0,
                    %xmm0 under AVX
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: craig.topper at gmail.com
                CC: llvm-bugs at lists.llvm.org

For this IR under AVX, we should be able to use "vcvtdq2pd %xmm0, %xmm0".

define <2 x double> @sitofp_4i32_to_2f64(<4 x i32> %a) {
  ; SSE-LABEL: sitofp_4i32_to_2f64:
  ; SSE:       # %bb.0:
  ; SSE-NEXT:    cvtdq2pd %xmm0, %xmm0
  ; SSE-NEXT:    retq
  ;
  ; AVX-LABEL: sitofp_4i32_to_2f64:
  ; AVX:       # %bb.0:
  ; AVX-NEXT:    vcvtdq2pd %xmm0, %ymm0
  ; AVX-NEXT:    # kill: def $xmm0 killed $xmm0 killed $ymm0
  ; AVX-NEXT:    vzeroupper
  ; AVX-NEXT:    retq
  %cvt = sitofp <4 x i32> %a to <4 x double>
  %shuf = shufflevector <4 x double> %cvt, <4 x double> undef, <2 x i32> <i32
0, i32 1>
   ret <2 x double> %shuf
}


We probably need a DAG combine to merge the extract_subvector we get from the
shuffle.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20180315/65054ca5/attachment.html>