[PATCH 0/3] Rework early return and hot/cold label predictors

[marxin]

Hello.

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%

to:

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
statement.

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?
Martin

marxin (3):
  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(-)

-- 
2.13.0