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Diffstat (limited to 'gcc/doc/tm.texi')
| -rw-r--r-- | gcc/doc/tm.texi | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index d3d9c1e..78f2f2f 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -842,6 +842,25 @@ pointer. If this macro is defined, GCC will turn on the @option{-fomit-frame-pointer} option whenever @option{-O} is specified. @end defmac +@defmac SWITCHABLE_TARGET +Some targets need to switch between substantially different subtargets +during compilation. For example, the MIPS target has one subtarget for +the traditional MIPS architecture and another for MIPS16. Source code +can switch between these two subarchitectures using the @code{mips16} +and @code{nomips16} attributes. + +Such subtargets can differ in things like the set of available +registers, the set of available instructions, the costs of various +operations, and so on. GCC caches a lot of this type of information +in global variables, and recomputing them for each subtarget takes a +significant amount of time. The compiler therefore provides a facility +for maintaining several versions of the global variables and quickly +switching between them; see @file{target-globals.h} for details. + +Define this macro to 1 if your target needs this facility. The default +is 0. +@end defmac + @node Per-Function Data @section Defining data structures for per-function information. @cindex per-function data |