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To: Scott Robert Ladd <coyote@coyotegulch.com>
Cc: Roger Sayle <roger@eyesopen.com>, gcc@gcc.gnu.org
Subject: Re: GCC viciously beaten by ICC in trig test!
References: <Pine.LNX.4.44.0403141713460.12909-100000@www.eyesopen.com>
	<40551459.8050909@coyotegulch.com>
From: Gabriel Dos Reis <gdr@integrable-solutions.net>
In-Reply-To: <40551459.8050909@coyotegulch.com>
Organization: Integrable Solutions
Date: Mon, 15 Mar 2004 03:05:00 -0000
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Scott Robert Ladd <coyote@coyotegulch.com> writes:

| Roger Sayle wrote:
| > Consider the following:
| > #include <math.h>
| > double doit(double a) { return sin(a) * sin(a); }
| > Compiling with gcc -O2 -ffast-math on Linux generates x86 code that's
| >  significantly slower than Intel's compiler output.  However,
| > commenting out the "#include <math.h>" corrects the situation and GCC
| > can then generate *exactly* the same sequence as icc.
| 
| Wonderful! This is *exactly* the insight I was looking for...

Note that it has been reported in the past the the x86 native
instruction fsin yields incorrect results for values outside or a
certain interval (I can't remember which exactly). 

[...]

| Sometimes, I wonder if GCC should ship its own Standard C library, just
| as it ships a Standard C++ template library. However, I suspect the
| suggesting such a move might be a bit controversial... ;)

Yep, but it would make V3 happy ;-)

-- Gaby