From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1923) id F0F393854568; Thu, 17 Nov 2022 22:25:32 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F0F393854568 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1668723932; bh=EM7m5+ARoRFM2vbdxkWDcUqAzmM54FcNL3tf7bLS06g=; h=From:To:Subject:Date:From; b=Yxa1IoMIVkob0b8mu9sLJCvFU7v6YY70LIiuMYDBePPli7L+wCaJKxYD1TD+YbNhZ La6QnsnaKAIytZ3OdeM7ZWsp28l45VqKlC4I9N0FFDn8PQcoMBRJwITYgs0bmKX6oQ QUYSEAT1ZEPJsdi8+fVGAmsVSwSB6FXWw0B+PSHk= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Philipp Tomsich To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/vendors/vrull/heads/for-upstream)] ifcombine: fold two bit tests with different polarity X-Act-Checkin: gcc X-Git-Author: Philipp Tomsich X-Git-Refname: refs/vendors/vrull/heads/for-upstream X-Git-Oldrev: 8b07e6237fc161def658c1d26d17d631c14309af X-Git-Newrev: 05980169d616eca7a17d3cac91d98437198bbcdb Message-Id: <20221117222532.F0F393854568@sourceware.org> Date: Thu, 17 Nov 2022 22:25:32 +0000 (GMT) List-Id: https://gcc.gnu.org/g:05980169d616eca7a17d3cac91d98437198bbcdb commit 05980169d616eca7a17d3cac91d98437198bbcdb Author: Philipp Tomsich Date: Sun Oct 16 22:35:08 2022 +0200 ifcombine: fold two bit tests with different polarity Our ifcombine pass combines 2 single-bit tests into a single test of the form "(a & T) == T", requiring the same polarity (i.e., tests for bit set/cleared) for both bit-tests. However some applications test against two bits expecting one set and the other cleared. This adds support for the case "(a & T) == C" where T is a constant with 2 bits set and C has only one of those bits set. gcc/ChangeLog: * tree-ssa-ifcombine.cc (ifcombine_ifandif): Add support for combining two bit-tests that test for bits of different polarity. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/ssa-ifcombine-15.c: New test. Series-to: gcc-patches@gcc.gnu.org Series-cc: Richard Biener Series-cc: Tamar Christina Series-cc: Jiang-Ning Liu Series-cc: Christoph Muellner Series-cc: Jeff Law Diff: --- gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-15.c | 14 ++++++ gcc/tree-ssa-ifcombine.cc | 56 ++++++++++++++++++++++++ 2 files changed, 70 insertions(+) diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-15.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-15.c new file mode 100644 index 00000000000..081faa39628 --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-ifcombine-15.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-ifcombine-details-blocks" } */ + +void sink(); + +void reversed(unsigned char *a) +{ + if (*a & 0x60) + if (!(*a & 0x02)) + g(); +} + +/* { dg-final { scan-tree-dump "optimizing double bit test" } } */ + diff --git a/gcc/tree-ssa-ifcombine.cc b/gcc/tree-ssa-ifcombine.cc index cd6331f84db..ea49cc2bff1 100644 --- a/gcc/tree-ssa-ifcombine.cc +++ b/gcc/tree-ssa-ifcombine.cc @@ -498,6 +498,62 @@ ifcombine_ifandif (basic_block inner_cond_bb, bool inner_inv, return true; } + /* See if we test polarity-reversed single bits of the same name in + both tests. In that case remove the outer test, merging both + else edges, and change the inner one to test for + name & (bit1 | bit2) == (bit2). */ + else if ((recognize_single_bit_test (inner_cond, &name1, &bit1, !inner_inv) + && recognize_single_bit_test (outer_cond, &name2, &bit2, outer_inv) + && name1 == name2) + || (recognize_single_bit_test (inner_cond, &name2, &bit2, inner_inv) + && recognize_single_bit_test (outer_cond, &name1, &bit1, !outer_inv) + && name1 == name2)) + { + tree t, t2, t3; + + /* Do it. */ + gsi = gsi_for_stmt (inner_cond); + t = fold_build2 (LSHIFT_EXPR, TREE_TYPE (name1), + build_int_cst (TREE_TYPE (name1), 1), bit1); + t2 = fold_build2 (LSHIFT_EXPR, TREE_TYPE (name1), + build_int_cst (TREE_TYPE (name1), 1), bit2); + t = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (name1), t, t2); + t = force_gimple_operand_gsi (&gsi, t, true, NULL_TREE, + true, GSI_SAME_STMT); + t3 = fold_build2 (BIT_AND_EXPR, TREE_TYPE (name1), name1, t); + t3 = force_gimple_operand_gsi (&gsi, t3, true, NULL_TREE, + true, GSI_SAME_STMT); + t = fold_build2 (result_inv ? NE_EXPR : EQ_EXPR, + boolean_type_node, t2, t3); + t = canonicalize_cond_expr_cond (t); + if (!t) + return false; + gimple_cond_set_condition_from_tree (inner_cond, t); + update_stmt (inner_cond); + + /* Leave CFG optimization to cfg_cleanup. */ + gimple_cond_set_condition_from_tree (outer_cond, + outer_inv ? boolean_false_node : boolean_true_node); + update_stmt (outer_cond); + + update_profile_after_ifcombine (inner_cond_bb, outer_cond_bb); + + if (dump_file) + { + fprintf (dump_file, "optimizing double bit test to "); + print_generic_expr (dump_file, name1); + fprintf (dump_file, " & T == C\nwith temporary T = (1 << "); + print_generic_expr (dump_file, bit1); + fprintf (dump_file, ") | (1 << "); + print_generic_expr (dump_file, bit2); + fprintf (dump_file, ")\nand temporary C = (1 << "); + print_generic_expr (dump_file, bit2); + fprintf (dump_file, ")\n"); + } + + return true; + } + /* See if we have two bit tests of the same name in both tests. In that case remove the outer test and change the inner one to test for name & (bits1 | bits2) != 0. */