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From: Philipp Tomsich <ptomsich@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/vendors/vrull/heads/for-upstream)] ifcombine: fold two bit tests with different polarity Date: Thu, 17 Nov 2022 22:25:32 +0000 (GMT) [thread overview] Message-ID: <20221117222532.F0F393854568@sourceware.org> (raw) https://gcc.gnu.org/g:05980169d616eca7a17d3cac91d98437198bbcdb commit 05980169d616eca7a17d3cac91d98437198bbcdb Author: Philipp Tomsich <philipp.tomsich@vrull.eu> 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 <rguenther@suse.de> Series-cc: Tamar Christina <tamar.christina@arm.com> Series-cc: Jiang-Ning Liu <jiangning.liu@amperecomputing.com> Series-cc: Christoph Muellner <christoph.muellner@vrull.eu> Series-cc: Jeff Law <jlaw@ventanamicro.com> 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. */
next reply other threads:[~2022-11-17 22:25 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-17 22:25 Philipp Tomsich [this message] -- strict thread matches above, loose matches on Subject: below -- 2022-11-18 20:25 Philipp Tomsich 2022-11-18 20:22 Philipp Tomsich 2022-11-18 11:34 Philipp Tomsich 2022-11-15 14:01 Philipp Tomsich
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