Re: [Boost-build] Suggestions for additional features / options for compiler toolsets: special instructions and floating point

From: Vladimir Prus (ghost_at_[hidden])
Date: 2007-12-01 13:34:51

On Friday 16 November 2007 21:44:04 John Pavel wrote:
> Just as it is possible to invoke, eg, async exceptions by means of
> 
> project
>   : requirements 
>     <toolset>msvc:<asynch-exceptions>on
>   ; 
> 
> it would be helpful to be able to set a few other flags, notably for
> different types of special instruction and floating point handling:
> 
> 
> More specifically, could we invoke the use of SSE instructions?
> 
> In gcc, this is done by the -mssse, -mssse2, etc, flags.  gcc 4.3.0 also
> provides 
> . Support for SSSE3 built-in functions and code generation are available via
> -mssse3 (which also comes with the core2 architecture)
> . Support for SSE4.1 built-in functions and code generation are available
> via -msse4.1. 
> . Support for SSE4.2 built-in functions and code generation are available
> via -msse4.2. 
> 
> (see http://gcc.gnu.org/gcc-4.3/changes.html)
> 
> VC++ has the /arch option (see
> http://msdn2.microsoft.com/en-gb/library/7t5yh4fd(VS.90).aspx) Intel has
> similar.
> 
> 
> Could we also invoke different types of floating point handling:
> 
> For recent versions of VC++ (and Intel compilers) we have /fp:[precise |
> except[-] | fast | strict ] (see
> http://msdn2.microsoft.com/en-gb/library/e7s85ffb(VS.90).aspx)
> 
> Gcc has a similar, if more finely grained, set of options.
> 
> These options would be even more useful if combined with the ability to time
> the running of tests, as it would allow the user to test the impact of using
> faster v more accurate fp handling.

I'm not sure. Are those options present in other compilers, in basically
same form. It's probably not worth adding a feature if it's easy to
accomplish using explicit options, and there are just two compilers of interest.

- Volodya