[LLVMbugs] [Bug 13787] New: unnecessary register spill (AVX)

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http://llvm.org/bugs/show_bug.cgi?id=13787

             Bug #: 13787
           Summary: unnecessary register spill (AVX)
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: matt at pharr.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 9177
  --> http://llvm.org/bugs/attachment.cgi?id=9177
bitcode

The attached test case seems to have some unnecessary register spills.  See,
for example the block LBB0_3, which has the sequence:

    vbroadcastss    (%r9), %ymm7
[...]
    vmovaps    %ymm7, 992(%rsp)
[...] # no other changes to %r9
    addq    $4, %r9
[...] # no uses of %r9
    vmovaps    992(%rsp), %ymm13
    # % ymm13 is now used...

Unless I'm missing something (and this has happened before...), I believe that
this could be more efficiently done as

    vbroadcastss (%r9), %ymm13
    addq    $4, %r9
    # use % ymm13

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