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[PATCH 0/3] Rework early return and hot/cold label predictors
- From: marxin <mliska at suse dot cz>
- To: gcc-patches at gcc dot gnu dot org
- Cc: hubicka at ucw dot cz
- Date: Tue, 6 Jun 2017 10:59:32 +0200
- Subject: [PATCH 0/3] Rework early return and hot/cold label predictors
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As mentioned in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79489#c1
early-return predictors is currenty not much precise. I decided to
come up with GIMPLE_PREDICT statement that I put early and thus
more precise numbers can be seen.
For SPEC 2017 we can improve the predictor from:
HEURISTICS BRANCHES (REL) BR. HITRATE HITRATE COVERAGE COVERAGE (REL) predict.def (REL)
early return (on trees) 17804 11.7% 63.54% 55.14% / 85.46% 38154989508 38.15G 5.4% 54% 1.1%
early return (on trees) 3692 4.1% 79.55% 66.22% / 76.14% 15778842701 15.78G 2.4% 66% 0.2%
For tests I had to change couple of tailrecursion tests, where recursion
happens in tailr2 pass. It's not done in tailr1 due to GIMPLE_PREDICT
Apart from that I would like to add a sanity unit tests for values
of predictors. And finally, I was asked by Honza to transform cold/hot
label predictors to GIMPLE_PREDICT as well.
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
Ready to be installed?
Come up with selftests for predict.c.
Make early return predictor more precise.
Rework cold and hot label attributes in predict.c.
gcc/gimple-low.c | 3 +
gcc/gimple-predict.h | 8 ++
gcc/gimplify.c | 26 +++++-
gcc/predict.c | 103 +++++++++---------------
gcc/predict.def | 15 +---
gcc/selftest-run-tests.c | 1 +
gcc/selftest.h | 1 +
gcc/testsuite/gcc.dg/tree-ssa/attr-hotcold-2.c | 4 +-
gcc/testsuite/gcc.dg/tree-ssa/tailrecursion-1.c | 4 +-
gcc/testsuite/gcc.dg/tree-ssa/tailrecursion-2.c | 4 +-
gcc/testsuite/gcc.dg/tree-ssa/tailrecursion-6.c | 4 +-
gcc/tree-inline.c | 7 ++
12 files changed, 95 insertions(+), 85 deletions(-)