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

From: John Pavel (jrp_at_[hidden])
Date: 2007-11-16 13:44:04

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.