[v3] combine: perform jump threading at the end

Message ID	20180910105919.19602-1-iii@linux.ibm.com
State	New
Headers	show Return-Path: <gcc-patches-return-485392-incoming=patchwork.ozlabs.org@gcc.gnu.org> DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:cc:subject:date:message-id; q=dns; s=default; b=g1KfbvwK/hun xUizmVSIScqPaAiKxHRfkakZ077Xuv1SUdvxKWTfVpjPOQNKvPJSQM/3XcEkEbnj YmFoa4/gmEOS2xzXI9/ijOA/yXFelj3v6bnw0i960XOSTGz0b4vCIoGCAVZB1Aff BsThH34F5vbWgKIRFUmiPLqif6wyc+s= Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk Sender: gcc-patches-owner@gcc.gnu.org Gateway: Authorized Use Only! Violators will be prosecuted for <gcc-patches@gcc.gnu.org> from <iii@linux.ibm.com>; Mon, 10 Sep 2018 11:59:28 +0100 Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 10 Sep 2018 11:59:26 +0100 From: Ilya Leoshkevich <iii@linux.ibm.com> To: gcc-patches@gcc.gnu.org Cc: krebbel@linux.ibm.com, rdapp@linux.ibm.com, richard.guenther@gmail.com, segher@kernel.crashing.org, Ilya Leoshkevich <iii@linux.ibm.com> Subject: [PATCH v3] combine: perform jump threading at the end Date: Mon, 10 Sep 2018 12:59:19 +0200 Message-Id: <20180910105919.19602-1-iii@linux.ibm.com>
Series	[v3] combine: perform jump threading at the end \| expand [v3] combine: perform jump threading at the end

diff --git a/gcc/combine.c b/gcc/combine.c index a2649b6d5a1..65f5d7d092b 100644 --- a/gcc/combine.c +++ b/gcc/combine.c @@ -1139,13 +1139,42 @@ insn_a_feeds_b (rtx_insn *a, rtx_insn *b) return false; } +/* Return true iff the only side effect of BB is its trailing jump_insn. */ + +static bool +is_single_jump_bb (basic_block bb) +{ + rtx_insn *end = BB_END (bb); + rtx_insn *insn; + + if (!JUMP_P (end)) + return false; + + for (insn = BB_HEAD (bb); insn != end; insn = NEXT_INSN (insn)) + if (INSN_P (insn) && side_effects_p (PATTERN (insn))) + return false; + return true; +} + +/* Summary of changes performed by the combiner. */ +struct combine_summary { + /* True if the combiner has turned an indirect jump instruction into a direct + jump. */ + bool new_direct_jump_p; + + /* True if the combiner changed at least one basic block in a way that it + ended up containing a single jump_insn. */ + bool new_single_jump_p; +}; + /* Main entry point for combiner. F is the first insn of the function. NREGS is the first unused pseudo-reg number. - Return nonzero if the combiner has turned an indirect jump - instruction into a direct jump. */ -static int -combine_instructions (rtx_insn *f, unsigned int nregs) + If performed changes satisfy certain criteria, set the corresponding fields + of SUMMARY to true. */ +static void +combine_instructions (rtx_insn *f, unsigned int nregs, + struct combine_summary *summary) { rtx_insn *insn, *next; rtx_insn *prev; @@ -1158,7 +1187,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) for (first = f; first && !NONDEBUG_INSN_P (first); ) first = NEXT_INSN (first); if (!first) - return 0; + return; combine_attempts = 0; combine_merges = 0; @@ -1251,6 +1280,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) FOR_EACH_BB_FN (this_basic_block, cfun) { rtx_insn *last_combined_insn = NULL; + bool bb_changed = false; /* Ignore instruction combination in basic blocks that are going to be removed as unreachable anyway. See PR82386. */ @@ -1302,6 +1332,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "two-insn combine", 1); + bb_changed = true; goto retry; } @@ -1323,6 +1354,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "three-insn combine", 1); + bb_changed = true; goto retry; } } @@ -1349,7 +1381,10 @@ combine_instructions (rtx_insn *f, unsigned int nregs) if ((next = try_combine (insn, prev, nextlinks->insn, NULL, &new_direct_jump_p, last_combined_insn)) != 0) - goto retry; + { + bb_changed = true; + goto retry; + } } /* Do the same for an insn that explicitly references CC0. */ @@ -1363,13 +1398,19 @@ combine_instructions (rtx_insn *f, unsigned int nregs) if ((next = try_combine (insn, prev, NULL, NULL, &new_direct_jump_p, last_combined_insn)) != 0) - goto retry; + { + bb_changed = true; + goto retry; + } FOR_EACH_LOG_LINK (nextlinks, prev) if ((next = try_combine (insn, prev, nextlinks->insn, NULL, &new_direct_jump_p, last_combined_insn)) != 0) + { + bb_changed = true; goto retry; + } } /* Finally, see if any of the insns that this insn links to @@ -1387,7 +1428,10 @@ combine_instructions (rtx_insn *f, unsigned int nregs) && (next = try_combine (insn, links->insn, prev, NULL, &new_direct_jump_p, last_combined_insn)) != 0) - goto retry; + { + bb_changed = true; + goto retry; + } } /* Try combining an insn with two different insns whose results it @@ -1403,6 +1447,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) { statistics_counter_event (cfun, "three-insn combine", 1); + bb_changed = true; goto retry; } @@ -1431,6 +1476,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "four-insn combine", 1); + bb_changed = true; goto retry; } /* I0, I1 -> I2, I2 -> I3. */ @@ -1442,6 +1488,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "four-insn combine", 1); + bb_changed = true; goto retry; } } @@ -1459,6 +1506,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "four-insn combine", 1); + bb_changed = true; goto retry; } /* I0 -> I1; I1, I2 -> I3. */ @@ -1469,6 +1517,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) last_combined_insn)) != 0) { statistics_counter_event (cfun, "four-insn combine", 1); + bb_changed = true; goto retry; } } @@ -1510,6 +1559,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs) if (next) { statistics_counter_event (cfun, "insn-with-note combine", 1); + bb_changed = true; goto retry; } SET_SRC (set) = orig_src; @@ -1523,6 +1573,10 @@ combine_instructions (rtx_insn *f, unsigned int nregs) retry: ; } + + if (flag_thread_jumps) + summary->new_single_jump_p + |= bb_changed && is_single_jump_bb (this_basic_block); } default_rtl_profile (); @@ -1557,7 +1611,7 @@ retry: /* Make recognizer allow volatile MEMs again. */ init_recog (); - return new_direct_jump_p; + summary->new_direct_jump_p = new_direct_jump_p; } /* Wipe the last_xxx fields of reg_stat in preparation for another pass. */ @@ -14939,7 +14993,7 @@ dump_combine_total_stats (FILE *file) static unsigned int rest_of_handle_combine (void) { - int rebuild_jump_labels_after_combine; + struct combine_summary summary; df_set_flags (DF_LR_RUN_DCE + DF_DEFER_INSN_RESCAN); df_note_add_problem (); @@ -14948,22 +15002,25 @@ rest_of_handle_combine (void) regstat_init_n_sets_and_refs (); reg_n_sets_max = max_reg_num (); - rebuild_jump_labels_after_combine - = combine_instructions (get_insns (), max_reg_num ()); + memset (&summary, 0, sizeof (summary)); + combine_instructions (get_insns (), max_reg_num (), &summary); /* Combining insns may have turned an indirect jump into a direct jump. Rebuild the JUMP_LABEL fields of jumping instructions. */ - if (rebuild_jump_labels_after_combine) + if (summary.new_direct_jump_p) { if (dom_info_available_p (CDI_DOMINATORS)) free_dominance_info (CDI_DOMINATORS); - timevar_push (TV_JUMP); rebuild_jump_labels (get_insns ()); - cleanup_cfg (0); - timevar_pop (TV_JUMP); } + /* Combining insns can change basic blocks in a way that they end up + containing a single jump_insn. This creates an opportunity to improve + code with jump threading. */ + if (summary.new_direct_jump_p || summary.new_single_jump_p) + cleanup_cfg (summary.new_single_jump_p ? CLEANUP_THREADING : 0); + regstat_free_n_sets_and_refs (); return 0; } diff --git a/gcc/testsuite/gcc.target/s390/pr80080-4.c b/gcc/testsuite/gcc.target/s390/pr80080-4.c new file mode 100644 index 00000000000..91d31ec7845 --- /dev/null +++ b/gcc/testsuite/gcc.target/s390/pr80080-4.c @@ -0,0 +1,16 @@ +/* { dg-do compile } */ +/* { dg-options "-march=z196 -O2" } */ + +extern void bar(int *mem); + +void foo4(int *mem) +{ + int oldval = 0; + if (!__atomic_compare_exchange_n (mem, (void *) &oldval, 1, + 1, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) + { + bar (mem); + } +} + +/* { dg-final { scan-assembler "\n\tlt\t.*\n\tjne\t(\\.L\\d+)\n(.*\n)*\tcs\t.*\n\tber\t%r14\n\\1:\n\tjg\tbar\n" } } */

[v3] combine: perform jump threading at the end

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