[Bug rtl-optimization/80799] New: [7 Regression] x86-32 bits generates MMX without EMMS

[gregory.hainaut at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80799

            Bug ID: 80799
           Summary: [7 Regression] x86-32 bits generates MMX without EMMS
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gregory.hainaut at gmail dot com
  Target Milestone: ---

Created attachment 41373
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41373&action=edit
MMX without EMMS instead of SSE2

Dear GCC developers,

GCC7 breaks the build of the project PCSX2. We found that MMX opcodes are
generated without any EMMS opcode on the 32 bits build (compiled from x86-64).
Note: it would likely be better to use the SSE2 equivalent opcode.

Please find a small example attached. Compiled with : g++  -msse -msse2 -O2
-m32 -g -c gcc7_mmx.cpp

Here the generated code

GIFRegHandlerTRXPOS(GIFRegTRXPOS const&):
        push    ebx
        sub     esp, 8
        mov     ebx, DWORD PTR [esp+16]
        movq    xmm0, QWORD PTR TRXPOS

        movq    mm0, QWORD PTR [ebx]
        movq2dq xmm1, mm0

        pcmpeqd xmm0, xmm1
        pmovmskb        eax, xmm0
        cmp     eax, 65535
        je      .L2
        call    dummy_call()

        movq    mm0, QWORD PTR [ebx]
.L2:
        movq    QWORD PTR TRXPOS, mm0

        add     esp, 8
        pop     ebx
        ret

Best Regards,
Gregory