[Bug target/56560] New: [4.7 regression] vzeroupper clobbers argument with AVX

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56560



             Bug #: 56560

           Summary: [4.7 regression] vzeroupper clobbers argument with AVX

    Classification: Unclassified

           Product: gcc

           Version: 4.7.3

            Status: UNCONFIRMED

          Keywords: wrong-code

          Severity: normal

          Priority: P3

         Component: target

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: ebotca...@gcc.gnu.org

            Target: x86_64-*-*





The vzeroupper optimization pass can go awry on the 4.7 branch and clobbers

arguments passed to functions:



eric@polaris:~> cat t.c

/* { dg-do compile } */

/* { dg-options "-O2 -mavx" } */



extern void abort (void);



typedef double vec_t __attribute__((vector_size(32)));



struct S { int i1; int i2; int i3; };



extern int bar (vec_t, int, int, int, int, int, struct S);



void foo (vec_t v, struct S s)

{

  int i = bar (v, 1, 2, 3, 4, 5, s);

  if (i == 0)

    abort ();

}



/* { dg-final { scan-assembler-not "vzeroupper" } } */

eric@polaris:~> ~/install/gcc-4_7-branch/bin/gcc -S -O2 -mavx t.c

eric@polaris:~> cat t.s

        .file   "t.c"

        .text

        .p2align 4,,15

        .globl  foo

        .type   foo, @function

foo:

.LFB0:

        .cfi_startproc

        pushq   %rbp

        .cfi_def_cfa_offset 16

        .cfi_offset 6, -16

        movl    $5, %r8d

        movl    $4, %ecx

        movl    $3, %edx

        movq    %rsp, %rbp

        .cfi_def_cfa_register 6

        andq    $-32, %rsp

        subq    $64, %rsp

        movq    %rdi, (%rsp)

        movl    %esi, 8(%rsp)

        movl    $1, %edi

        movl    $2, %esi

        vzeroupper

        call    bar

        testl   %eax, %eax

        je      .L5

        leave

        .cfi_remember_state

        .cfi_def_cfa 7, 8

        ret

.L5:

        .cfi_restore_state

        .p2align 4,,9

        call    abort

        .cfi_endproc