From 7b1ff60122fda6e106e54b792713f8eb16424cf2 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Mon, 10 Dec 2018 21:56:54 -0700 Subject: re PR tree-optimization/80520 (Performance regression from missing if-conversion) PR tree-optimization/80520 * gimple-ssa-split-paths.c (is_feasible_trace): Recognize half diamonds that are likely if convertable. * gcc.dg/tree-ssa/split-path-5.c: Update expected output. * gcc.dg/tree-ssa/split-path-11.c: New test. From-SVN: r266971 --- gcc/gimple-ssa-split-paths.c | 92 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) (limited to 'gcc/gimple-ssa-split-paths.c') diff --git a/gcc/gimple-ssa-split-paths.c b/gcc/gimple-ssa-split-paths.c index a851511..9159652 100644 --- a/gcc/gimple-ssa-split-paths.c +++ b/gcc/gimple-ssa-split-paths.c @@ -203,6 +203,98 @@ is_feasible_trace (basic_block bb) } } + /* Canonicalize the form. */ + if (num_stmts_in_pred1 == 0 && num_stmts_in_pred2 == 1) + { + std::swap (pred1, pred2); + std::swap (num_stmts_in_pred1, num_stmts_in_pred2); + } + + /* Another variant. This one is half-diamond. */ + if (num_stmts_in_pred1 == 1 && num_stmts_in_pred2 == 0 + && dominated_by_p (CDI_DOMINATORS, pred1, pred2)) + { + gimple *stmt1 = last_and_only_stmt (pred1); + + /* The only statement in PRED1 must be an assignment that is + not a good candidate for if-conversion. This may need some + generalization. */ + if (stmt1 && gimple_code (stmt1) == GIMPLE_ASSIGN) + { + enum tree_code code1 = gimple_assign_rhs_code (stmt1); + + if (!poor_ifcvt_candidate_code (code1)) + { + tree lhs1 = gimple_assign_lhs (stmt1); + tree rhs1 = gimple_assign_rhs1 (stmt1); + + gimple_stmt_iterator gsi; + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple *phi = gsi_stmt (gsi); + if ((gimple_phi_arg_def (phi, 0) == lhs1 + && gimple_phi_arg_def (phi, 1) == rhs1) + || (gimple_phi_arg_def (phi, 1) == lhs1 + && gimple_phi_arg_def (phi, 0) == rhs1)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Block %d appears to be a join point for " + "if-convertable half-diamond.\n", + bb->index); + return false; + } + } + } + } + } + + /* Canonicalize the form. */ + if (num_stmts_in_pred1 == 0 && num_stmts_in_pred2 == 1) + { + std::swap (pred1, pred2); + std::swap (num_stmts_in_pred1, num_stmts_in_pred2); + } + + /* Another variant. This one is half-diamond. */ + if (num_stmts_in_pred1 == 1 && num_stmts_in_pred2 == 0 + && dominated_by_p (CDI_DOMINATORS, pred1, pred2)) + { + gimple *stmt1 = last_and_only_stmt (pred1); + + /* The only statement in PRED1 must be an assignment that is + not a good candidate for if-conversion. This may need some + generalization. */ + if (stmt1 && gimple_code (stmt1) == GIMPLE_ASSIGN) + { + enum tree_code code1 = gimple_assign_rhs_code (stmt1); + + if (!poor_ifcvt_candidate_code (code1)) + { + tree lhs1 = gimple_assign_lhs (stmt1); + tree rhs1 = gimple_assign_rhs1 (stmt1); + + gimple_stmt_iterator gsi; + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple *phi = gsi_stmt (gsi); + if ((gimple_phi_arg_def (phi, 0) == lhs1 + && gimple_phi_arg_def (phi, 1) == rhs1) + || (gimple_phi_arg_def (phi, 1) == lhs1 + && gimple_phi_arg_def (phi, 0) == rhs1)) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Block %d appears to be a join point for " + "if-convertable half-diamond.\n", + bb->index); + return false; + } + } + } + } + } + /* If the joiner has no PHIs with useful uses there is zero chance of CSE/DCE/jump-threading possibilities exposed by duplicating it. */ bool found_useful_phi = false; -- cgit v1.1