diff options
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/config/rs6000/rs6000.c | 7 |
2 files changed, 9 insertions, 3 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 20e16f2..c2df5a0 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2016-01-28 Pat Haugen <pthaugen@us.ibm.com> + + * config/rs6000/rs6000.c (output_cbranch): Don't statically predict + branches if using guessed profile. + 2016-01-28 H.J. Lu <hongjiu.lu@intel.com> * graphite-optimize-isl.c (optimize_isl): Fix dump. diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index e9e12f5..41f53ad 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -21432,14 +21432,15 @@ output_cbranch (rtx op, const char *label, int reversed, rtx_insn *insn) /* PROB is the difference from 50%. */ int prob = XINT (note, 0) - REG_BR_PROB_BASE / 2; - /* Only hint for highly probable/improbable branches on newer - cpus as static prediction overrides processor dynamic - prediction. For older cpus we may as well always hint, but + /* Only hint for highly probable/improbable branches on newer cpus when + we have real profile data, as static prediction overrides processor + dynamic prediction. For older cpus we may as well always hint, but assume not taken for branches that are very close to 50% as a mispredicted taken branch is more expensive than a mispredicted not-taken branch. */ if (rs6000_always_hint || (abs (prob) > REG_BR_PROB_BASE / 100 * 48 + && (profile_status_for_fn (cfun) != PROFILE_GUESSED) && br_prob_note_reliable_p (note))) { if (abs (prob) > REG_BR_PROB_BASE / 20 |