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| author | Martin Liska <mliska@suse.cz> | 2019-07-09 11:22:30 +0200 |
|---|---|---|
| committer | Martin Liska <marxin@gcc.gnu.org> | 2019-07-09 09:22:30 +0000 |
| commit | b52db15861e60f5ca82b63caabed6a00da98c7d7 (patch) | |
| tree | 857cb570588eecc0f1aa364494278c4b04ce7318 /gcc | |
| parent | c2851dc2896bfc0d27b32c90cafc873f67cd6727 (diff) | |
| download | gcc-b52db15861e60f5ca82b63caabed6a00da98c7d7.zip gcc-b52db15861e60f5ca82b63caabed6a00da98c7d7.tar.gz gcc-b52db15861e60f5ca82b63caabed6a00da98c7d7.tar.bz2 | |
Document and test __builtin_expect_with_probability.
2019-07-09 Martin Liska <mliska@suse.cz>
* doc/extend.texi: Document influence on loop
optimizers.
2019-07-09 Martin Liska <mliska@suse.cz>
* gcc.dg/predict-17.c: Test loop optimizer assumption
about loop iterations.
From-SVN: r273295
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/extend.texi | 5 | ||||
| -rw-r--r-- | gcc/testsuite/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/predict-17.c | 4 |
4 files changed, 17 insertions, 2 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 8fccc6b..5072a03 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -8,6 +8,11 @@ 2019-07-09 Martin Liska <mliska@suse.cz> + * doc/extend.texi: Document influence on loop + optimizers. + +2019-07-09 Martin Liska <mliska@suse.cz> + * lto-compress.c (lto_normalized_zstd_level): Do not use ZSTD_CLEVEL_DEFAULT as it is not default in old releases of libzstd. One can use 0 as a default compression level. diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index f2619e1..0616074 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -13045,8 +13045,11 @@ when testing pointer or floating-point values. For the purposes of branch prediction optimizations, the probability that a @code{__builtin_expect} expression is @code{true} is controlled by GCC's @code{builtin-expect-probability} parameter, which defaults to 90%. + You can also use @code{__builtin_expect_with_probability} to explicitly -assign a probability value to individual expressions. +assign a probability value to individual expressions. If the built-in +is used in a loop construct, the provided probability will influence +the expected number of iterations made by loop optimizations. @end deftypefn @deftypefn {Built-in Function} long __builtin_expect_with_probability diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index e9d0195..ce78f77 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2019-07-09 Martin Liska <mliska@suse.cz> + + * gcc.dg/predict-17.c: Test loop optimizer assumption + about loop iterations. + 2019-07-09 Richard Biener <rguenther@suse.de> * gcc.dg/tree-ssa/alias-access-path-1.c: Scan fre1 dump. diff --git a/gcc/testsuite/gcc.dg/predict-17.c b/gcc/testsuite/gcc.dg/predict-17.c index 5069aa4..45b618a 100644 --- a/gcc/testsuite/gcc.dg/predict-17.c +++ b/gcc/testsuite/gcc.dg/predict-17.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -fdump-tree-profile_estimate" } */ +/* { dg-options "-O2 -fdump-tree-profile_estimate-details" } */ extern int global; @@ -11,3 +11,5 @@ void foo (int base) /* { dg-final { scan-tree-dump "first match heuristics: 5.00%" "profile_estimate"} } */ /* { dg-final { scan-tree-dump "__builtin_expect_with_probability heuristics of edge .*->.*: 5.00%" "profile_estimate"} } */ +/* { dg-final { scan-tree-dump "is probably executed at most 19" "profile_estimate"} } */ + |