[Bug rtl-optimization/109052] Unnecessary reload with -mfpmath=both

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109052

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
The original testcase is:

double foo (double a, double b)
{
  double z = __builtin_fmod (a, 3.14);
  return z * b;
}

-O2 -fno-math-errno:

foo:
        fldl    .LC0(%rip)
        movsd   %xmm0, -8(%rsp)
        fldl    -8(%rsp)
.L2:
        fprem
        fnstsw  %ax
        testb   $4, %ah
        jne     .L2
        fstp    %st(1)
        fstpl   -8(%rsp)
-->     movsd   -8(%rsp), %xmm0
        mulsd   %xmm1, %xmm0
        ret

and with -mavx:

foo:
        fldl    .LC0(%rip)
        vmovsd  %xmm0, -8(%rsp)
        fldl    -8(%rsp)
.L2:
        fprem
        fnstsw  %ax
        testb   $4, %ah
        jne     .L2
        fstp    %st(1)
        fstpl   -8(%rsp)
-->     vmovsd  -8(%rsp), %xmm0
        vmulsd  %xmm1, %xmm0, %xmm0
        ret