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From: Alexandre Oliva <aoliva@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/aoliva/heads/testme)] [PR105455] Set edge probabilities when hardening conditionals Date: Wed, 11 May 2022 09:36:12 +0000 (GMT) [thread overview] Message-ID: <20220511093612.265DA395B432@sourceware.org> (raw) https://gcc.gnu.org/g:bd8212013e1f74d7c84add7cfa70c6d79a84e02a commit bd8212013e1f74d7c84add7cfa70c6d79a84e02a Author: Alexandre Oliva <oliva@adacore.com> Date: Wed May 11 04:27:42 2022 -0300 [PR105455] Set edge probabilities when hardening conditionals When turning unconditional edges into conditional, as in gimple-harden-conditionals.cc:insert_check_and_trap, the newly-created edge's probability comes out uninitialized, while the previously unconditional edge's probability is presumably profile_probability::always. Mixing initialized and uninitialized probabilities before expand breaks predict.cc:force_edge_cold: the initialized probability may end up copied to a REG_BR_PROB note in a conditional branch insn, but if force_edge_cold is called on that edge, it will find another edge with uninitialized probability and assume the note is absent. Later on, rtl_verify_edges complains that the note does not match the probability modified by force_edge_cold in the edge. This patch sets probabilities for edges affected by hardening of conditionals, both the newly-created edges to trap blocks and the previously-unconditional edges, so that the former are considered never taken, while the latter are confirmed as always taken. for gcc/ChangeLog PR rtl-optimization/105455 * gimple-harden-conditionals.cc (insert_check_and_trap): Set probabilities for newly-conditional edges. for gcc/testsuite/ChangeLog PR rtl-optimization/105455 * gcc.dg/pr105455.c: New. Diff: --- gcc/gimple-harden-conditionals.cc | 2 ++ gcc/testsuite/gcc.dg/pr105455.c | 17 +++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/gcc/gimple-harden-conditionals.cc b/gcc/gimple-harden-conditionals.cc index 28c4810f0a7..240d0e5acd8 100644 --- a/gcc/gimple-harden-conditionals.cc +++ b/gcc/gimple-harden-conditionals.cc @@ -254,8 +254,10 @@ insert_check_and_trap (location_t loc, gimple_stmt_iterator *gsip, equality. */ single_succ_edge (chk)->flags &= ~EDGE_FALLTHRU; single_succ_edge (chk)->flags |= neg_true_false_flag; + single_succ_edge (chk)->probability = profile_probability::always (); edge e = make_edge (chk, trp, true_false_flag); e->goto_locus = loc; + e->probability = profile_probability::never (); if (dom_info_available_p (CDI_DOMINATORS)) set_immediate_dominator (CDI_DOMINATORS, trp, chk); diff --git a/gcc/testsuite/gcc.dg/pr105455.c b/gcc/testsuite/gcc.dg/pr105455.c new file mode 100644 index 00000000000..81e9154baa1 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr105455.c @@ -0,0 +1,17 @@ +/* { dg-do compile } */ +/* { dg-options "-O1 -fharden-conditional-branches -funroll-loops --param max-loop-header-insns=1" } */ + +__attribute__ ((cold)) void +bar (void); + +void +foo (int x) +{ + if (x) + { + int i; + + for (i = 0; i < 101; ++i) + bar (); + } +}
next reply other threads:[~2022-05-11 9:36 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-11 9:36 Alexandre Oliva [this message] -- strict thread matches above, loose matches on Subject: below -- 2022-05-11 7:32 Alexandre Oliva
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