-fast

Optimize for speed of execution using a selection of options.

SPARC: 77/90 x86:77

Select options that optimize for speed of execution without excessive compilation time. This option provides close-to-the-maximum performance for many applications.

If you compile and link in separate steps, and you compile with -fast, then be sure to link with -fast.

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Note -

This option is defined as a particular selection of other options that is subject to change from one release to another, and between compilers. Also, some of the options selected by -fast may not be available on some platforms.

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Table 3-15 -fast selections across platforms

SPARC	x86
-dalign	--
-depend	--
-fns	-fns
-fsimple=1	--
-ftrap=%none	-ftrap=%none
-libmil (f77) -f      (f90)	-libmil
-native	-native
--	-nofstore
-O4	-O4
-xlibmopt	-xlibmopt

Details about the options selected by -fast:

• The -native hardware target. If the program is intended to run on a different target than the compilation machine, follow the -fast with a code-generator option. For example: f77 -fast xtarget=ultra ...

• The -O4 optimization level option.

• The -depend option (SPARC only).

• The -libmil option for system-supplied inline expansion templates. For C functions that depend on exception handling, follow -fast by -nolibmil: -fast -nolibmil. With -libmil, exceptions cannot be detected with errno or matherr(3m).

• The -fsimple=1 option for a simple floating-point model. -fsimple is unsuitable if strict IEEE 754 standards compliance is required.

• The -dalign option to generate double loads and stores (SPARC only). Using this option may generate nonstandard Fortran data alignment.

• The -xlibmopt option (SPARC only)

• -nofstore (x86 only)

• -fns -ftrap=%none to turn off all trapping.

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  Note -

  With f90, the -f option is substituted for -libmil  on SPARC.

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It is possible to add or subtract from this list by following the -fast option with other options, as in:

f77 -fast -fsimple=2 -xnolibmopt ...

which overrides the -fsimple=1 option and disables the -xlibmopt selected by -fast.