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From: "neleai at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug other/56631] New: duplicated sse code in switch
Date: Sat, 16 Mar 2013 11:35:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56631

             Bug #: 56631
           Summary: duplicated sse code in switch
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: neleai@seznam.cz


Consider attached testcase. When compiled with -Os,-O2,-O3 it duplicates
zeroing xmm1 register across all branches. Moving zeroing before braches will
save space.

Relevant assembly at -Os is

  jmp *.L19(,%rax,8)
  .section  .rodata
  .align 8
  .align 4
.L19:
  .quad .L21
  .quad .L4
  .quad .L5
snip 

.L21:
  xorps %xmm1, %xmm1
.L38:
  movaps  %xmm0, %xmm2
  pcmpeqb %xmm1, %xmm2
  pmovmskb  %xmm2, %eax
  testl %eax, %eax
  jne .L1
.L2:
  movdqu  %xmm0, (%rdi)
  addq  $64, %rdi
  movups  64(%rsi), %xmm0
  addq  $64, %rsi
  jmp .L38
.L4:
  xorps %xmm1, %xmm1
  incq  %rdi
.L23:
snip
.L5:
  xorps %xmm1, %xmm1
  addq  $2, %rdi