[Bug target/52933] SH Target: Use div0s for integer sign comparisons

[olegendo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52933

--- Comment #4 from Oleg Endo <olegendo at gcc dot gnu.org> ---
The div0s insn can also be used to do floating point sign comparisons.  For
example:

bool test3 (float x, float y)
{
  return __builtin_signbitf (x) ^ __builtin_signbitf (y);
}

currently compiles to:

        flds    fr4,fpul
        sts     fpul,r2
        flds    fr5,fpul
        sts     fpul,r3
        mov.l   .L7,r1
        and     r1,r2
        and     r3,r1
        cmp/eq  r1,r2
        movt    r0
        rts
        xor     #1,r0
.L8:
        .align 2
.L7:
        .long   -2147483648

better:
        flds    fr4,fpul
        sts     fpul,r2
        flds    fr5,fpul
        sts     fpul,r3
        div0s   r2,r3
        rts
        movt    r0


The same goes for negated result value of the sign comparison:

bool test3_1 (float x, float y)
{
  return !(__builtin_signbitf (x) ^ __builtin_signbitf (y));
}

Currently compiles to:

        flds    fr4,fpul
        sts     fpul,r2
        flds    fr5,fpul
        sts     fpul,r3
        mov.l   .L11,r1
        and     r1,r2
        and     r3,r1
        cmp/eq  r1,r2
        rts
        movt    r0
.L12:
        .align 2
.L11:
        .long   -2147483648

better:
        flds    fr4,fpul
        sts     fpul,r2
        flds    fr5,fpul
        sts     fpul,r3
        div0s   r2,r3
        mov     #-1,r0    // on SH2A should use movrt
        rts
        negc    r0,r0