https://gcc.gnu.org/g:bae9c5e7c6efc0cbed9ea98c4c58bf7ed341f68d
commit r16-4164-gbae9c5e7c6efc0cbed9ea98c4c58bf7ed341f68d Author: Jan Hubicka <[email protected]> Date: Wed Oct 1 16:51:26 2025 +0200 Propagate unlikely executed BBs even on measured profiles While looking into AutoFDO porfiles I noticed that sometimes we lost precise zero counts due to inlining and merging basic blocks. Propagating precise zero counts should be safe even for measured profiles and thus this patch enables it. gcc/ChangeLog: * predict.cc (unlikely_executed_stmt_p): Remove redundant check. (rebuild_frequencies): Also recompute unlikely bbs when profile is present or consistent. Diff: --- gcc/predict.cc | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/gcc/predict.cc b/gcc/predict.cc index 5639d81d2770..895c5f959d02 100644 --- a/gcc/predict.cc +++ b/gcc/predict.cc @@ -852,7 +852,7 @@ unlikely_executed_stmt_p (gimple *stmt) heuristics. */ if (gimple_bb (stmt)->count.reliable_p () && gimple_bb (stmt)->count.nonzero_p ()) - return gimple_bb (stmt)->count == profile_count::zero (); + return false; /* NORETURN attribute alone is not strong enough: exit() may be quite likely executed once during program run. */ if (gimple_call_fntype (stmt) @@ -4521,6 +4521,9 @@ rebuild_frequencies (void) && (!uninitialized_count_found || uninitialized_probablity_found) && !cfun->cfg->count_max.very_large_p ()) { + /* Propagating zero counts should be safe and may + help hot/cold splitting. */ + determine_unlikely_bbs (); if (dump_file) fprintf (dump_file, "Profile is consistent\n"); return; @@ -4545,6 +4548,9 @@ rebuild_frequencies (void) for a given run, we would only propagate the error further. */ if (feedback_found && !uninitialized_count_found) { + /* Propagating zero counts should be safe and may + help hot/cold splitting. */ + determine_unlikely_bbs (); if (dump_file) fprintf (dump_file, "Profile is inconsistent but read from profile feedback;"
