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| author | Roger Sayle <roger@eyesopen.com> | 2004-05-19 13:54:15 +0000 |
|---|---|---|
| committer | Roger Sayle <sayle@gcc.gnu.org> | 2004-05-19 13:54:15 +0000 |
| commit | 31a52b868a209f0c8f3ade10a91148664526dc9b (patch) | |
| tree | 2708e7bc3111a8f768bf18005fc086587b092f1b /gcc | |
| parent | d28f752bd30791925d7c6fbf08cf426026cd3279 (diff) | |
| download | gcc-31a52b868a209f0c8f3ade10a91148664526dc9b.zip gcc-31a52b868a209f0c8f3ade10a91148664526dc9b.tar.gz gcc-31a52b868a209f0c8f3ade10a91148664526dc9b.tar.bz2 | |
tm.texi (TARGET_RTX_COSTS): Document that instruction costs should be based on code size when...
* doc/tm.texi (TARGET_RTX_COSTS): Document that instruction
costs should be based on code size when optimizing for size.
From-SVN: r82025
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/tm.texi | 8 |
2 files changed, 12 insertions, 1 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 3b61615..ca2069d 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2004-05-19 Roger Sayle <roger@eyesopen.com> + + * doc/tm.texi (TARGET_RTX_COSTS): Document that instruction + costs should be based on code size when optimizing for size. + 2004-05-19 Paolo Bonzini <bonzini@gnu.org> * fold-const.c: Remove non-printable character 160. diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index 43543a8..67f4b76 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -5456,7 +5456,13 @@ instructions. On entry to the hook, @code{*@var{total}} contains a default estimate for the cost of the expression. The hook should modify this value as -necessary. +necessary. Traditionally, the default costs are @code{COSTS_N_INSNS (5)} +for multiplications, @code{COSTS_N_INSNS (7)} for division and modulus +operations, and @code{COSTS_N_INSNS (1)} for all other operations. + +When optimizing for code size, i.e@. when @code{optimize_size} is +non-zero, this target hook should be used to estimate the relative +size cost of an expression, again relative to @code{COSTS_N_INSNS}. The hook returns true when all subexpressions of @var{x} have been processed, and false when @code{rtx_cost} should recurse. |