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Re: [BENCHMARK]-mfpmath=sse should disable x387 intrinsics
- From: Roger Sayle <roger at eyesopen dot com>
- To: Richard Guenther <richard dot guenther at gmail dot com>
- Cc: Uros Bizjak <uros at kss-loka dot si>, <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 25 Nov 2004 09:40:12 -0700 (MST)
- Subject: Re: [BENCHMARK]-mfpmath=sse should disable x387 intrinsics
On Thu, 25 Nov 2004, Richard Guenther wrote:
> Also, out IP optimization could change the ABI for static functions to
> not have the penalty of returning on the FP stack, testcase (compile
> with -fno-inline -mfpmath=sse):
> static double foo(double x)
> return x*x;
> double bar(double y)
> y = 2*y+foo(y);
> return y;
You could try -mno-fp-ret-in-387 which produces much prettier code but
breaks standard ABIs. Indeed, the 386.c backend could probably be tweaked
to implictly perform the equivalent of "-mno-fp-ret-in-387" when using
"-mfpmath=sse" for static functions within a single compilation unit.
Alternatively, it could also perform the equivalent of a hypothetical
"-mfp-ret-in-sse" in exactly these cases too.