diff options
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 b5cb240..0abf394 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -8800,6 +8800,25 @@ Define this macro on machine that have comparison operations that return floating-point values. If there are no such operations, do not define this macro. +@findex CLZ_DEFINED_VALUE_AT_ZERO +@findex CTZ_DEFINED_VALUE_AT_ZERO +@item CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) +@itemx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value}) +A C expression that evaluates to true if the architecture defines a value +for @code{clz} or @code{ctz} with a zero operand. If so, @var{value} +should be set to this value. If this macro is not defined, the value of +@code{clz} or @code{ctz} is assumed to be undefined. + +This macro must be defined if the target's expansion for @code{ffs} +relies on a particular value to get correct results. Otherwise it +is not necessary, though it may be used to optimize some corner cases. + +Note that regardless of this macro the ``definedness'' of @code{clz} +and @code{ctz} at zero do @emph{not} extend to the builtin functions +visible to the user. Thus one may be free to adjust the value at will +to match the target expansion of these operations without fear of +breaking the API. + @findex Pmode @item Pmode An alias for the machine mode for pointers. On most machines, define |