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From: "z.zhanghaijian at huawei dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/94665] missed minmax optimization opportunity
 for if/else structure.
Date: Mon, 20 Apr 2020 08:12:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94665

--- Comment #6 from z.zhanghaijian at huawei dot com <z.zhanghaijian at hua=
wei dot com> ---
(In reply to Segher Boessenkool from comment #5)
> Can you show the  -fdump-rtl-combine-all  dump where that insn is
> created?
>=20
> It is fine to generate min or max insns here; but you need to handle the=
=20
> case where vara is NaN: you should return that NaN then.  Other than that
> your function is just the max of vara, varb, varc.

The dump info=EF=BC=9A

Trying 39 -> 40:
   39: cc:CCFPE=3Dcmp(r94:SF,r93:SF)
   40: r94:SF=3D{(cc:CCFPE<0)?r94:SF:r93:SF}
      REG_DEAD r93:SF
      REG_DEAD cc:CCFPE
Successfully matched this instruction:
(set (reg:SF 94 [ _4 ])
    (smin:SF (reg:SF 94 [ _4 ])
        (reg:SF 93 [ _2 ])))
allowing combination of insns 39 and 40
original costs 4 + 4 =3D 8
replacement cost 8
deferring deletion of insn with uid =3D 39.
modifying insn i3    40: r94:SF=3Dsmin(r94:SF,r93:SF)
      REG_DEAD r93:SF
deferring rescan insn with uid =3D 40.=