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Re: A new patch for floating point conditional mov on PPo
- To: john at feith dot com (John Wehle)
- Subject: Re: A new patch for floating point conditional mov on PPo
- From: hjl at lucon dot org (H.J. Lu)
- Date: Wed, 10 Jun 1998 09:16:58 -0700 (PDT)
- Cc: law at cygnus dot com, egcs-patches at cygnus dot com
>
> Another output_int_test_compare_fcmov issue is that it clobbers cc0.
>
> Consider:
>
> int a;
> int b;
> double d;
> double e;
> int g;
> int h;
>
> if (a < b)
> d = f;
>
> if (a < b)
> g = h;
>
It seems to me that the second (a < b) is never deleted even for
int
foo (int x, int i, int y, int z)
{
if (y > z)
x = 0;
if (y > z)
i = 0;
return x * i;
}
I think it is a good thing since the compiler may not know if
the body of if_then_else will clobber cc0. If there is a way
to tell the compiler about clobbering cc0, we just tell the
compiler that the fp conditional move may clobber cc0.
My signed int comparison patch looks ok to me :-).
H.J.