Re: GCC's -ffast-math behavior

[Andrew Haley <aph@xxxxxxxxxx>]

On 02/09/2012 10:20 AM, xunxun wrote:
> I use the code main.c (test sin speed)
> 
> On Win7 64bit, gcc 4.6.2 32bit
> 
> gcc -O3 -ffast-math main.c -o main.exe
> 
> run main.exe will cost 6.853s.
> 
> When linking with intel libM no fastmath
> 
> gcc -O3 main.c -o main.exe libmmt.lib libircmt.lib
> 
> run main.exe will cost 4.367s.

Ah okay, I get it now, its sin, not exp.  I suspect that it's the
argument reduction step that's slowing you down.

Andrew.