[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: unassigned@gcc.gnu.org
        ReportedBy: ebotcazou@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