[Bug target/58110] New: Useless GPR push and pop when only xmm registers are used.

["neleai at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58110

            Bug ID: 58110
           Summary: Useless GPR push and pop when only xmm registers are
                    used.
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: neleai at seznam dot cz

Hi,attached code generates extra push/pop rbx pair while there is no gpr
register assigned in segment between them.
This was generated by head xgcc -O3. A gcc-4.7 has similar issues with attached
program.

  pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        movdqu  (%rsi), %xmm15
        movdqu  -16(%rsi,%rdx), %xmm14
        movdqu  16(%rsi), %xmm13
        movdqu  -32(%rsi,%rdx), %xmm12
        movdqu  32(%rsi), %xmm11
        movdqu  -48(%rsi,%rdx), %xmm10
        movdqu  48(%rsi), %xmm9
        movdqu  -64(%rsi,%rdx), %xmm8
        movdqu  64(%rsi), %xmm7
        movdqu  -80(%rsi,%rdx), %xmm6
        movdqu  80(%rsi), %xmm5
        movdqu  -96(%rsi,%rdx), %xmm4
        movdqu  96(%rsi), %xmm3
        movdqu  -112(%rsi,%rdx), %xmm2
        movdqu  112(%rsi), %xmm1
        movdqu  -128(%rsi,%rdx), %xmm0
        movdqu  %xmm15, (%rdi)
        movdqu  %xmm14, -16(%rdi,%rdx)
        movdqu  %xmm13, 16(%rdi)
        movdqu  %xmm12, -32(%rdi,%rdx)
        movdqu  %xmm11, 32(%rdi)
        movdqu  %xmm10, -48(%rdi,%rdx)
        movdqu  %xmm9, 48(%rdi)
        movdqu  %xmm8, -64(%rdi,%rdx)
        movdqu  %xmm7, 64(%rdi)
        movdqu  %xmm6, -80(%rdi,%rdx)
        movdqu  %xmm5, 80(%rdi)
        movdqu  %xmm4, -96(%rdi,%rdx)
        movdqu  %xmm3, 96(%rdi)
        movdqu  %xmm2, -112(%rdi,%rdx)
        movdqu  %xmm1, 112(%rdi)
        movdqu  %xmm0, -128(%rdi,%rdx)
        popq    %rbx