diff options
Diffstat (limited to 'gcc/tree-ssa-pre.c')
| -rw-r--r-- | gcc/tree-ssa-pre.c | 93 |
1 files changed, 88 insertions, 5 deletions
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c index ed326e40303..54770c8eea9 100644 --- a/gcc/tree-ssa-pre.c +++ b/gcc/tree-ssa-pre.c @@ -2597,6 +2597,7 @@ can_PRE_operation (tree op) for performing quick dead code elimination of insertions we made that didn't turn out to be necessary. */ static VEC(gimple,heap) *inserted_exprs; +static bitmap inserted_phi_names; /* Pool allocated fake store expressions are placed onto this worklist, which, after performing dead code elimination, is walked @@ -3242,6 +3243,8 @@ insert_into_preds_of_block (basic_block block, unsigned int exprnum, VN_INFO_GET (gimple_phi_result (phi))->valnum = gimple_phi_result (phi); VN_INFO (gimple_phi_result (phi))->value_id = val; VEC_safe_push (gimple, heap, inserted_exprs, phi); + bitmap_set_bit (inserted_phi_names, + SSA_NAME_VERSION (gimple_phi_result (phi))); FOR_EACH_EDGE (pred, ei, block->preds) { pre_expr ae = avail[pred->src->index]; @@ -4129,16 +4132,95 @@ eliminate (void) } } } + + for (gsi = gsi_start_phis (b); !gsi_end_p (gsi);) + { + gimple stmt, phi = gsi_stmt (gsi); + tree sprime = NULL_TREE, res = PHI_RESULT (phi); + pre_expr sprimeexpr, resexpr; + gimple_stmt_iterator gsi2; + + /* We want to perform redundant PHI elimination. Do so by + replacing the PHI with a single copy if possible. + Do not touch inserted, single-argument or virtual PHIs. */ + if (gimple_phi_num_args (phi) == 1 + || !is_gimple_reg (res) + || bitmap_bit_p (inserted_phi_names, SSA_NAME_VERSION (res))) + { + gsi_next (&gsi); + continue; + } + + resexpr = get_or_alloc_expr_for_name (res); + sprimeexpr = bitmap_find_leader (AVAIL_OUT (b), + get_expr_value_id (resexpr), NULL); + if (sprimeexpr) + { + if (sprimeexpr->kind == CONSTANT) + sprime = PRE_EXPR_CONSTANT (sprimeexpr); + else if (sprimeexpr->kind == NAME) + sprime = PRE_EXPR_NAME (sprimeexpr); + else + gcc_unreachable (); + } + if (!sprimeexpr + || sprime == res) + { + gsi_next (&gsi); + continue; + } + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Replaced redundant PHI node defining "); + print_generic_expr (dump_file, res, 0); + fprintf (dump_file, " with "); + print_generic_expr (dump_file, sprime, 0); + fprintf (dump_file, "\n"); + } + + remove_phi_node (&gsi, false); + + stmt = gimple_build_assign (res, sprime); + SSA_NAME_DEF_STMT (res) = stmt; + if (TREE_CODE (sprime) == SSA_NAME) + gimple_set_plf (SSA_NAME_DEF_STMT (sprime), + NECESSARY, true); + gsi2 = gsi_after_labels (b); + gsi_insert_before (&gsi2, stmt, GSI_NEW_STMT); + /* Queue the copy for eventual removal. */ + VEC_safe_push (gimple, heap, to_remove, stmt); + pre_stats.eliminations++; + } } /* We cannot remove stmts during BB walk, especially not release SSA - names there as this confuses the VN machinery. */ + names there as this confuses the VN machinery. The stmts ending + up in to_remove are either stores or simple copies. */ for (i = 0; VEC_iterate (gimple, to_remove, i, stmt); ++i) { - gsi = gsi_for_stmt (stmt); - unlink_stmt_vdef (stmt); - gsi_remove (&gsi, true); - release_defs (stmt); + tree lhs = gimple_assign_lhs (stmt); + use_operand_p use_p; + gimple use_stmt; + + /* If there is a single use only, propagate the equivalency + instead of keeping the copy. */ + if (TREE_CODE (lhs) == SSA_NAME + && single_imm_use (lhs, &use_p, &use_stmt)) + { + SET_USE (use_p, gimple_assign_rhs1 (stmt)); + update_stmt (use_stmt); + } + + /* If this is a store or a now unused copy, remove it. */ + if (TREE_CODE (lhs) != SSA_NAME + || has_zero_uses (lhs)) + { + gsi = gsi_for_stmt (stmt); + unlink_stmt_vdef (stmt); + gsi_remove (&gsi, true); + release_defs (stmt); + } } VEC_free (gimple, heap, to_remove); @@ -4296,6 +4378,7 @@ init_pre (bool do_fre) calculate_dominance_info (CDI_DOMINATORS); bitmap_obstack_initialize (&grand_bitmap_obstack); + inserted_phi_names = BITMAP_ALLOC (&grand_bitmap_obstack); phi_translate_table = htab_create (5110, expr_pred_trans_hash, expr_pred_trans_eq, free); expression_to_id = htab_create (num_ssa_names * 3, |