diff options
Diffstat (limited to 'gcc/doc/tm.texi')
| -rw-r--r-- | gcc/doc/tm.texi | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index 0ec10c5949d..a913b8058c6 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -5897,12 +5897,30 @@ will be used. Defaults to 1 if @code{move_by_pieces_ninsns} returns less than @code{CLEAR_RATIO}. @end defmac +@defmac SET_RATIO +The threshold of number of scalar move insns, @emph{below} which a sequence +of insns should be generated to set memory to a constant value, instead of +a block set insn or a library call. +Increasing the value will always make code faster, but +eventually incurs high cost in increased code size. + +If you don't define this, it defaults to the value of @code{MOVE_RATIO}. +@end defmac + +@defmac SET_BY_PIECES_P (@var{size}, @var{alignment}) +A C expression used to determine whether @code{store_by_pieces} will be +used to set a chunk of memory to a constant value, or whether some +other mechanism will be used. Used by @code{__builtin_memset} when +storing values other than constant zero. +Defaults to 1 if @code{move_by_pieces_ninsns} returns less +than @code{SET_RATIO}. +@end defmac + @defmac STORE_BY_PIECES_P (@var{size}, @var{alignment}) A C expression used to determine whether @code{store_by_pieces} will be -used to set a chunk of memory to a constant value, or whether some other -mechanism will be used. Used by @code{__builtin_memset} when storing -values other than constant zero and by @code{__builtin_strcpy} when -when called with a constant source string. +used to set a chunk of memory to a constant string value, or whether some +other mechanism will be used. Used by @code{__builtin_strcpy} when +called with a constant source string. Defaults to 1 if @code{move_by_pieces_ninsns} returns less than @code{MOVE_RATIO}. @end defmac |