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Diffstat (limited to 'gcc/doc/tm.texi')
| -rw-r--r-- | gcc/doc/tm.texi | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index 76a7b7e..fd2b370 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -5666,23 +5666,23 @@ insns with indexes greater than given index. @deftypefn {Target Hook} bool IS_COSTLY_DEPENDENCE (rtx @var{insn1}, rtx @var{insn2}, rtx @var{dep_link}, int @var{dep_cost}, int @var{distance}) This hook is used to define which dependences are considered costly by -the target, so costly that it is not advisable to schedule the insns that +the target, so costly that it is not advisable to schedule the insns that are involved in the dependence too close to one another. The parameters -to this hook are as follows: The second parameter @var{insn2} is dependent -upon the first parameter @var{insn1}. The dependence between @var{insn1} -and @var{insn2} is represented by the third parameter @var{dep_link}. The -fourth parameter @var{cost} is the cost of the dependence, and the fifth -parameter @var{distance} is the distance in cycles between the two insns. +to this hook are as follows: The second parameter @var{insn2} is dependent +upon the first parameter @var{insn1}. The dependence between @var{insn1} +and @var{insn2} is represented by the third parameter @var{dep_link}. The +fourth parameter @var{cost} is the cost of the dependence, and the fifth +parameter @var{distance} is the distance in cycles between the two insns. The hook returns @code{true} if considering the distance between the two insns the dependence between them is considered costly by the target, and @code{false} otherwise. Defining this hook can be useful in multiple-issue out-of-order machines, -where (a) it's practically hopeless to predict the actual data/resource +where (a) it's practically hopeless to predict the actual data/resource delays, however: (b) there's a better chance to predict the actual grouping -that will be formed, and (c) correctly emulating the grouping can be very +that will be formed, and (c) correctly emulating the grouping can be very important. In such targets one may want to allow issuing dependent insns -closer to one another - i.e, closer than the dependence distance; however, +closer to one another - i.e, closer than the dependence distance; however, not in cases of "costly dependences", which this hooks allows to define. @end deftypefn |