diff options
Diffstat (limited to 'gcc/doc/tm.texi.in')
| -rw-r--r-- | gcc/doc/tm.texi.in | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in index 9d10844..c53cbe8 100644 --- a/gcc/doc/tm.texi.in +++ b/gcc/doc/tm.texi.in @@ -6357,10 +6357,15 @@ Define this macro if a non-short-circuit operation produced by This target hook describes the relative costs of RTL expressions. The cost may depend on the precise form of the expression, which is -available for examination in @var{x}, and the rtx code of the expression -in which it is contained, found in @var{outer_code}. @var{code} is the -expression code---redundant, since it can be obtained with -@code{GET_CODE (@var{x})}. +available for examination in @var{x}, and the fact that @var{x} appears +as operand @var{opno} of an expression with rtx code @var{outer_code}. +That is, the hook can assume that there is some rtx @var{y} such +that @samp{GET_CODE (@var{y}) == @var{outer_code}} and such that +either (a) @samp{XEXP (@var{y}, @var{opno}) == @var{x}} or +(b) @samp{XVEC (@var{y}, @var{opno})} contains @var{x}. + +@var{code} is @var{x}'s expression code---redundant, since it can be +obtained with @code{GET_CODE (@var{x})}. In implementing this hook, you can use the construct @code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast |