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Diffstat (limited to 'contrib/gcc/tree-ssa-phiopt.c')
| -rw-r--r-- | contrib/gcc/tree-ssa-phiopt.c | 1022 |
1 files changed, 1022 insertions, 0 deletions
diff --git a/contrib/gcc/tree-ssa-phiopt.c b/contrib/gcc/tree-ssa-phiopt.c new file mode 100644 index 0000000..edad768 --- /dev/null +++ b/contrib/gcc/tree-ssa-phiopt.c @@ -0,0 +1,1022 @@ +/* Optimization of PHI nodes by converting them into straightline code. + Copyright (C) 2004, 2005 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it +under the terms of the GNU General Public License as published by the +Free Software Foundation; either version 2, or (at your option) any +later version. + +GCC is distributed in the hope that it will be useful, but WITHOUT +ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING. If not, write to the Free +Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301, USA. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "ggc.h" +#include "tree.h" +#include "rtl.h" +#include "flags.h" +#include "tm_p.h" +#include "basic-block.h" +#include "timevar.h" +#include "diagnostic.h" +#include "tree-flow.h" +#include "tree-pass.h" +#include "tree-dump.h" +#include "langhooks.h" + +static unsigned int tree_ssa_phiopt (void); +static bool conditional_replacement (basic_block, basic_block, + edge, edge, tree, tree, tree); +static bool value_replacement (basic_block, basic_block, + edge, edge, tree, tree, tree); +static bool minmax_replacement (basic_block, basic_block, + edge, edge, tree, tree, tree); +static bool abs_replacement (basic_block, basic_block, + edge, edge, tree, tree, tree); +static void replace_phi_edge_with_variable (basic_block, edge, tree, tree); +static basic_block *blocks_in_phiopt_order (void); + +/* This pass tries to replaces an if-then-else block with an + assignment. We have four kinds of transformations. Some of these + transformations are also performed by the ifcvt RTL optimizer. + + Conditional Replacement + ----------------------- + + This transformation, implemented in conditional_replacement, + replaces + + bb0: + if (cond) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <0 (bb1), 1 (bb0), ...>; + + with + + bb0: + x' = cond; + goto bb2; + bb2: + x = PHI <x' (bb0), ...>; + + We remove bb1 as it becomes unreachable. This occurs often due to + gimplification of conditionals. + + Value Replacement + ----------------- + + This transformation, implemented in value_replacement, replaces + + bb0: + if (a != b) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <a (bb1), b (bb0), ...>; + + with + + bb0: + bb2: + x = PHI <b (bb0), ...>; + + This opportunity can sometimes occur as a result of other + optimizations. + + ABS Replacement + --------------- + + This transformation, implemented in abs_replacement, replaces + + bb0: + if (a >= 0) goto bb2; else goto bb1; + bb1: + x = -a; + bb2: + x = PHI <x (bb1), a (bb0), ...>; + + with + + bb0: + x' = ABS_EXPR< a >; + bb2: + x = PHI <x' (bb0), ...>; + + MIN/MAX Replacement + ------------------- + + This transformation, minmax_replacement replaces + + bb0: + if (a <= b) goto bb2; else goto bb1; + bb1: + bb2: + x = PHI <b (bb1), a (bb0), ...>; + + with + + bb0: + x' = MIN_EXPR (a, b) + bb2: + x = PHI <x' (bb0), ...>; + + A similar transformation is done for MAX_EXPR. */ + +static unsigned int +tree_ssa_phiopt (void) +{ + basic_block bb; + basic_block *bb_order; + unsigned n, i; + bool cfgchanged = false; + + /* Search every basic block for COND_EXPR we may be able to optimize. + + We walk the blocks in order that guarantees that a block with + a single predecessor is processed before the predecessor. + This ensures that we collapse inner ifs before visiting the + outer ones, and also that we do not try to visit a removed + block. */ + bb_order = blocks_in_phiopt_order (); + n = n_basic_blocks - NUM_FIXED_BLOCKS; + + for (i = 0; i < n; i++) + { + tree cond_expr; + tree phi; + basic_block bb1, bb2; + edge e1, e2; + tree arg0, arg1; + + bb = bb_order[i]; + + cond_expr = last_stmt (bb); + /* Check to see if the last statement is a COND_EXPR. */ + if (!cond_expr + || TREE_CODE (cond_expr) != COND_EXPR) + continue; + + e1 = EDGE_SUCC (bb, 0); + bb1 = e1->dest; + e2 = EDGE_SUCC (bb, 1); + bb2 = e2->dest; + + /* We cannot do the optimization on abnormal edges. */ + if ((e1->flags & EDGE_ABNORMAL) != 0 + || (e2->flags & EDGE_ABNORMAL) != 0) + continue; + + /* If either bb1's succ or bb2 or bb2's succ is non NULL. */ + if (EDGE_COUNT (bb1->succs) == 0 + || bb2 == NULL + || EDGE_COUNT (bb2->succs) == 0) + continue; + + /* Find the bb which is the fall through to the other. */ + if (EDGE_SUCC (bb1, 0)->dest == bb2) + ; + else if (EDGE_SUCC (bb2, 0)->dest == bb1) + { + basic_block bb_tmp = bb1; + edge e_tmp = e1; + bb1 = bb2; + bb2 = bb_tmp; + e1 = e2; + e2 = e_tmp; + } + else + continue; + + e1 = EDGE_SUCC (bb1, 0); + + /* Make sure that bb1 is just a fall through. */ + if (!single_succ_p (bb1) + || (e1->flags & EDGE_FALLTHRU) == 0) + continue; + + /* Also make sure that bb1 only have one predecessor and that it + is bb. */ + if (!single_pred_p (bb1) + || single_pred (bb1) != bb) + continue; + + phi = phi_nodes (bb2); + + /* Check to make sure that there is only one PHI node. + TODO: we could do it with more than one iff the other PHI nodes + have the same elements for these two edges. */ + if (!phi || PHI_CHAIN (phi) != NULL) + continue; + + arg0 = PHI_ARG_DEF_TREE (phi, e1->dest_idx); + arg1 = PHI_ARG_DEF_TREE (phi, e2->dest_idx); + + /* Something is wrong if we cannot find the arguments in the PHI + node. */ + gcc_assert (arg0 != NULL && arg1 != NULL); + + /* Do the replacement of conditional if it can be done. */ + if (conditional_replacement (bb, bb1, e1, e2, phi, arg0, arg1)) + cfgchanged = true; + else if (value_replacement (bb, bb1, e1, e2, phi, arg0, arg1)) + cfgchanged = true; + else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1)) + cfgchanged = true; + else if (minmax_replacement (bb, bb1, e1, e2, phi, arg0, arg1)) + cfgchanged = true; + } + + free (bb_order); + + /* If the CFG has changed, we should cleanup the CFG. */ + return cfgchanged ? TODO_cleanup_cfg : 0; +} + +/* Returns the list of basic blocks in the function in an order that guarantees + that if a block X has just a single predecessor Y, then Y is after X in the + ordering. */ + +static basic_block * +blocks_in_phiopt_order (void) +{ + basic_block x, y; + basic_block *order = XNEWVEC (basic_block, n_basic_blocks); + unsigned n = n_basic_blocks - NUM_FIXED_BLOCKS; + unsigned np, i; + sbitmap visited = sbitmap_alloc (last_basic_block); + +#define MARK_VISITED(BB) (SET_BIT (visited, (BB)->index)) +#define VISITED_P(BB) (TEST_BIT (visited, (BB)->index)) + + sbitmap_zero (visited); + + MARK_VISITED (ENTRY_BLOCK_PTR); + FOR_EACH_BB (x) + { + if (VISITED_P (x)) + continue; + + /* Walk the predecessors of x as long as they have precisely one + predecessor and add them to the list, so that they get stored + after x. */ + for (y = x, np = 1; + single_pred_p (y) && !VISITED_P (single_pred (y)); + y = single_pred (y)) + np++; + for (y = x, i = n - np; + single_pred_p (y) && !VISITED_P (single_pred (y)); + y = single_pred (y), i++) + { + order[i] = y; + MARK_VISITED (y); + } + order[i] = y; + MARK_VISITED (y); + + gcc_assert (i == n - 1); + n -= np; + } + + sbitmap_free (visited); + gcc_assert (n == 0); + return order; + +#undef MARK_VISITED +#undef VISITED_P +} + +/* Return TRUE if block BB has no executable statements, otherwise return + FALSE. */ +bool +empty_block_p (basic_block bb) +{ + block_stmt_iterator bsi; + + /* BB must have no executable statements. */ + bsi = bsi_start (bb); + while (!bsi_end_p (bsi) + && (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR + || IS_EMPTY_STMT (bsi_stmt (bsi)))) + bsi_next (&bsi); + + if (!bsi_end_p (bsi)) + return false; + + return true; +} + +/* Replace PHI node element whose edge is E in block BB with variable NEW. + Remove the edge from COND_BLOCK which does not lead to BB (COND_BLOCK + is known to have two edges, one of which must reach BB). */ + +static void +replace_phi_edge_with_variable (basic_block cond_block, + edge e, tree phi, tree new) +{ + basic_block bb = bb_for_stmt (phi); + basic_block block_to_remove; + block_stmt_iterator bsi; + + /* Change the PHI argument to new. */ + SET_USE (PHI_ARG_DEF_PTR (phi, e->dest_idx), new); + + /* Remove the empty basic block. */ + if (EDGE_SUCC (cond_block, 0)->dest == bb) + { + EDGE_SUCC (cond_block, 0)->flags |= EDGE_FALLTHRU; + EDGE_SUCC (cond_block, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + EDGE_SUCC (cond_block, 0)->probability = REG_BR_PROB_BASE; + EDGE_SUCC (cond_block, 0)->count += EDGE_SUCC (cond_block, 1)->count; + + block_to_remove = EDGE_SUCC (cond_block, 1)->dest; + } + else + { + EDGE_SUCC (cond_block, 1)->flags |= EDGE_FALLTHRU; + EDGE_SUCC (cond_block, 1)->flags + &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE); + EDGE_SUCC (cond_block, 1)->probability = REG_BR_PROB_BASE; + EDGE_SUCC (cond_block, 1)->count += EDGE_SUCC (cond_block, 0)->count; + + block_to_remove = EDGE_SUCC (cond_block, 0)->dest; + } + delete_basic_block (block_to_remove); + + /* Eliminate the COND_EXPR at the end of COND_BLOCK. */ + bsi = bsi_last (cond_block); + bsi_remove (&bsi, true); + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "COND_EXPR in block %d and PHI in block %d converted to straightline code.\n", + cond_block->index, + bb->index); +} + +/* The function conditional_replacement does the main work of doing the + conditional replacement. Return true if the replacement is done. + Otherwise return false. + BB is the basic block where the replacement is going to be done on. ARG0 + is argument 0 from PHI. Likewise for ARG1. */ + +static bool +conditional_replacement (basic_block cond_bb, basic_block middle_bb, + edge e0, edge e1, tree phi, + tree arg0, tree arg1) +{ + tree result; + tree old_result = NULL; + tree new, cond; + block_stmt_iterator bsi; + edge true_edge, false_edge; + tree new_var = NULL; + tree new_var1; + + /* The PHI arguments have the constants 0 and 1, then convert + it to the conditional. */ + if ((integer_zerop (arg0) && integer_onep (arg1)) + || (integer_zerop (arg1) && integer_onep (arg0))) + ; + else + return false; + + if (!empty_block_p (middle_bb)) + return false; + + /* If the condition is not a naked SSA_NAME and its type does not + match the type of the result, then we have to create a new + variable to optimize this case as it would likely create + non-gimple code when the condition was converted to the + result's type. */ + cond = COND_EXPR_COND (last_stmt (cond_bb)); + result = PHI_RESULT (phi); + if (TREE_CODE (cond) != SSA_NAME + && !lang_hooks.types_compatible_p (TREE_TYPE (cond), TREE_TYPE (result))) + { + tree tmp; + + if (!COMPARISON_CLASS_P (cond)) + return false; + + tmp = create_tmp_var (TREE_TYPE (cond), NULL); + add_referenced_var (tmp); + new_var = make_ssa_name (tmp, NULL); + old_result = cond; + cond = new_var; + } + + /* If the condition was a naked SSA_NAME and the type is not the + same as the type of the result, then convert the type of the + condition. */ + if (!lang_hooks.types_compatible_p (TREE_TYPE (cond), TREE_TYPE (result))) + cond = fold_convert (TREE_TYPE (result), cond); + + /* We need to know which is the true edge and which is the false + edge so that we know when to invert the condition below. */ + extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge); + + /* Insert our new statement at the end of conditional block before the + COND_EXPR. */ + bsi = bsi_last (cond_bb); + bsi_insert_before (&bsi, build_empty_stmt (), BSI_NEW_STMT); + + if (old_result) + { + tree new1; + + new1 = build2 (TREE_CODE (old_result), TREE_TYPE (old_result), + TREE_OPERAND (old_result, 0), + TREE_OPERAND (old_result, 1)); + + new1 = build2 (MODIFY_EXPR, TREE_TYPE (old_result), new_var, new1); + SSA_NAME_DEF_STMT (new_var) = new1; + + bsi_insert_after (&bsi, new1, BSI_NEW_STMT); + } + + new_var1 = duplicate_ssa_name (PHI_RESULT (phi), NULL); + + + /* At this point we know we have a COND_EXPR with two successors. + One successor is BB, the other successor is an empty block which + falls through into BB. + + There is a single PHI node at the join point (BB) and its arguments + are constants (0, 1). + + So, given the condition COND, and the two PHI arguments, we can + rewrite this PHI into non-branching code: + + dest = (COND) or dest = COND' + + We use the condition as-is if the argument associated with the + true edge has the value one or the argument associated with the + false edge as the value zero. Note that those conditions are not + the same since only one of the outgoing edges from the COND_EXPR + will directly reach BB and thus be associated with an argument. */ + if ((e0 == true_edge && integer_onep (arg0)) + || (e0 == false_edge && integer_zerop (arg0)) + || (e1 == true_edge && integer_onep (arg1)) + || (e1 == false_edge && integer_zerop (arg1))) + { + new = build2 (MODIFY_EXPR, TREE_TYPE (new_var1), new_var1, cond); + } + else + { + tree cond1 = invert_truthvalue (cond); + + cond = cond1; + + /* If what we get back is a conditional expression, there is no + way that it can be gimple. */ + if (TREE_CODE (cond) == COND_EXPR) + { + release_ssa_name (new_var1); + return false; + } + + /* If COND is not something we can expect to be reducible to a GIMPLE + condition, return early. */ + if (is_gimple_cast (cond)) + cond1 = TREE_OPERAND (cond, 0); + if (TREE_CODE (cond1) == TRUTH_NOT_EXPR + && !is_gimple_val (TREE_OPERAND (cond1, 0))) + { + release_ssa_name (new_var1); + return false; + } + + /* If what we get back is not gimple try to create it as gimple by + using a temporary variable. */ + if (is_gimple_cast (cond) + && !is_gimple_val (TREE_OPERAND (cond, 0))) + { + tree op0, tmp, cond_tmp; + + /* Only "real" casts are OK here, not everything that is + acceptable to is_gimple_cast. Make sure we don't do + anything stupid here. */ + gcc_assert (TREE_CODE (cond) == NOP_EXPR + || TREE_CODE (cond) == CONVERT_EXPR); + + op0 = TREE_OPERAND (cond, 0); + tmp = create_tmp_var (TREE_TYPE (op0), NULL); + add_referenced_var (tmp); + cond_tmp = make_ssa_name (tmp, NULL); + new = build2 (MODIFY_EXPR, TREE_TYPE (cond_tmp), cond_tmp, op0); + SSA_NAME_DEF_STMT (cond_tmp) = new; + + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + cond = fold_convert (TREE_TYPE (result), cond_tmp); + } + + new = build2 (MODIFY_EXPR, TREE_TYPE (new_var1), new_var1, cond); + } + + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + + SSA_NAME_DEF_STMT (new_var1) = new; + + replace_phi_edge_with_variable (cond_bb, e1, phi, new_var1); + + /* Note that we optimized this PHI. */ + return true; +} + +/* The function value_replacement does the main work of doing the value + replacement. Return true if the replacement is done. Otherwise return + false. + BB is the basic block where the replacement is going to be done on. ARG0 + is argument 0 from the PHI. Likewise for ARG1. */ + +static bool +value_replacement (basic_block cond_bb, basic_block middle_bb, + edge e0, edge e1, tree phi, + tree arg0, tree arg1) +{ + tree cond; + edge true_edge, false_edge; + + /* If the type says honor signed zeros we cannot do this + optimization. */ + if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1)))) + return false; + + if (!empty_block_p (middle_bb)) + return false; + + cond = COND_EXPR_COND (last_stmt (cond_bb)); + + /* This transformation is only valid for equality comparisons. */ + if (TREE_CODE (cond) != NE_EXPR && TREE_CODE (cond) != EQ_EXPR) + return false; + + /* We need to know which is the true edge and which is the false + edge so that we know if have abs or negative abs. */ + extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge); + + /* At this point we know we have a COND_EXPR with two successors. + One successor is BB, the other successor is an empty block which + falls through into BB. + + The condition for the COND_EXPR is known to be NE_EXPR or EQ_EXPR. + + There is a single PHI node at the join point (BB) with two arguments. + + We now need to verify that the two arguments in the PHI node match + the two arguments to the equality comparison. */ + + if ((operand_equal_for_phi_arg_p (arg0, TREE_OPERAND (cond, 0)) + && operand_equal_for_phi_arg_p (arg1, TREE_OPERAND (cond, 1))) + || (operand_equal_for_phi_arg_p (arg1, TREE_OPERAND (cond, 0)) + && operand_equal_for_phi_arg_p (arg0, TREE_OPERAND (cond, 1)))) + { + edge e; + tree arg; + + /* For NE_EXPR, we want to build an assignment result = arg where + arg is the PHI argument associated with the true edge. For + EQ_EXPR we want the PHI argument associated with the false edge. */ + e = (TREE_CODE (cond) == NE_EXPR ? true_edge : false_edge); + + /* Unfortunately, E may not reach BB (it may instead have gone to + OTHER_BLOCK). If that is the case, then we want the single outgoing + edge from OTHER_BLOCK which reaches BB and represents the desired + path from COND_BLOCK. */ + if (e->dest == middle_bb) + e = single_succ_edge (e->dest); + + /* Now we know the incoming edge to BB that has the argument for the + RHS of our new assignment statement. */ + if (e0 == e) + arg = arg0; + else + arg = arg1; + + replace_phi_edge_with_variable (cond_bb, e1, phi, arg); + + /* Note that we optimized this PHI. */ + return true; + } + return false; +} + +/* The function minmax_replacement does the main work of doing the minmax + replacement. Return true if the replacement is done. Otherwise return + false. + BB is the basic block where the replacement is going to be done on. ARG0 + is argument 0 from the PHI. Likewise for ARG1. */ + +static bool +minmax_replacement (basic_block cond_bb, basic_block middle_bb, + edge e0, edge e1, tree phi, + tree arg0, tree arg1) +{ + tree result, type; + tree cond, new; + edge true_edge, false_edge; + enum tree_code cmp, minmax, ass_code; + tree smaller, larger, arg_true, arg_false; + block_stmt_iterator bsi, bsi_from; + + type = TREE_TYPE (PHI_RESULT (phi)); + + /* The optimization may be unsafe due to NaNs. */ + if (HONOR_NANS (TYPE_MODE (type))) + return false; + + cond = COND_EXPR_COND (last_stmt (cond_bb)); + cmp = TREE_CODE (cond); + result = PHI_RESULT (phi); + + /* This transformation is only valid for order comparisons. Record which + operand is smaller/larger if the result of the comparison is true. */ + if (cmp == LT_EXPR || cmp == LE_EXPR) + { + smaller = TREE_OPERAND (cond, 0); + larger = TREE_OPERAND (cond, 1); + } + else if (cmp == GT_EXPR || cmp == GE_EXPR) + { + smaller = TREE_OPERAND (cond, 1); + larger = TREE_OPERAND (cond, 0); + } + else + return false; + + /* We need to know which is the true edge and which is the false + edge so that we know if have abs or negative abs. */ + extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge); + + /* Forward the edges over the middle basic block. */ + if (true_edge->dest == middle_bb) + true_edge = EDGE_SUCC (true_edge->dest, 0); + if (false_edge->dest == middle_bb) + false_edge = EDGE_SUCC (false_edge->dest, 0); + + if (true_edge == e0) + { + gcc_assert (false_edge == e1); + arg_true = arg0; + arg_false = arg1; + } + else + { + gcc_assert (false_edge == e0); + gcc_assert (true_edge == e1); + arg_true = arg1; + arg_false = arg0; + } + + if (empty_block_p (middle_bb)) + { + if (operand_equal_for_phi_arg_p (arg_true, smaller) + && operand_equal_for_phi_arg_p (arg_false, larger)) + { + /* Case + + if (smaller < larger) + rslt = smaller; + else + rslt = larger; */ + minmax = MIN_EXPR; + } + else if (operand_equal_for_phi_arg_p (arg_false, smaller) + && operand_equal_for_phi_arg_p (arg_true, larger)) + minmax = MAX_EXPR; + else + return false; + } + else + { + /* Recognize the following case, assuming d <= u: + + if (a <= u) + b = MAX (a, d); + x = PHI <b, u> + + This is equivalent to + + b = MAX (a, d); + x = MIN (b, u); */ + + tree assign = last_and_only_stmt (middle_bb); + tree lhs, rhs, op0, op1, bound; + + if (!assign + || TREE_CODE (assign) != MODIFY_EXPR) + return false; + + lhs = TREE_OPERAND (assign, 0); + rhs = TREE_OPERAND (assign, 1); + ass_code = TREE_CODE (rhs); + if (ass_code != MAX_EXPR && ass_code != MIN_EXPR) + return false; + op0 = TREE_OPERAND (rhs, 0); + op1 = TREE_OPERAND (rhs, 1); + + if (true_edge->src == middle_bb) + { + /* We got here if the condition is true, i.e., SMALLER < LARGER. */ + if (!operand_equal_for_phi_arg_p (lhs, arg_true)) + return false; + + if (operand_equal_for_phi_arg_p (arg_false, larger)) + { + /* Case + + if (smaller < larger) + { + r' = MAX_EXPR (smaller, bound) + } + r = PHI <r', larger> --> to be turned to MIN_EXPR. */ + if (ass_code != MAX_EXPR) + return false; + + minmax = MIN_EXPR; + if (operand_equal_for_phi_arg_p (op0, smaller)) + bound = op1; + else if (operand_equal_for_phi_arg_p (op1, smaller)) + bound = op0; + else + return false; + + /* We need BOUND <= LARGER. */ + if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node, + bound, larger))) + return false; + } + else if (operand_equal_for_phi_arg_p (arg_false, smaller)) + { + /* Case + + if (smaller < larger) + { + r' = MIN_EXPR (larger, bound) + } + r = PHI <r', smaller> --> to be turned to MAX_EXPR. */ + if (ass_code != MIN_EXPR) + return false; + + minmax = MAX_EXPR; + if (operand_equal_for_phi_arg_p (op0, larger)) + bound = op1; + else if (operand_equal_for_phi_arg_p (op1, larger)) + bound = op0; + else + return false; + + /* We need BOUND >= SMALLER. */ + if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node, + bound, smaller))) + return false; + } + else + return false; + } + else + { + /* We got here if the condition is false, i.e., SMALLER > LARGER. */ + if (!operand_equal_for_phi_arg_p (lhs, arg_false)) + return false; + + if (operand_equal_for_phi_arg_p (arg_true, larger)) + { + /* Case + + if (smaller > larger) + { + r' = MIN_EXPR (smaller, bound) + } + r = PHI <r', larger> --> to be turned to MAX_EXPR. */ + if (ass_code != MIN_EXPR) + return false; + + minmax = MAX_EXPR; + if (operand_equal_for_phi_arg_p (op0, smaller)) + bound = op1; + else if (operand_equal_for_phi_arg_p (op1, smaller)) + bound = op0; + else + return false; + + /* We need BOUND >= LARGER. */ + if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node, + bound, larger))) + return false; + } + else if (operand_equal_for_phi_arg_p (arg_true, smaller)) + { + /* Case + + if (smaller > larger) + { + r' = MAX_EXPR (larger, bound) + } + r = PHI <r', smaller> --> to be turned to MIN_EXPR. */ + if (ass_code != MAX_EXPR) + return false; + + minmax = MIN_EXPR; + if (operand_equal_for_phi_arg_p (op0, larger)) + bound = op1; + else if (operand_equal_for_phi_arg_p (op1, larger)) + bound = op0; + else + return false; + + /* We need BOUND <= SMALLER. */ + if (!integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node, + bound, smaller))) + return false; + } + else + return false; + } + + /* Move the statement from the middle block. */ + bsi = bsi_last (cond_bb); + bsi_from = bsi_last (middle_bb); + bsi_move_before (&bsi_from, &bsi); + } + + /* Emit the statement to compute min/max. */ + result = duplicate_ssa_name (PHI_RESULT (phi), NULL); + new = build2 (MODIFY_EXPR, type, result, + build2 (minmax, type, arg0, arg1)); + SSA_NAME_DEF_STMT (result) = new; + bsi = bsi_last (cond_bb); + bsi_insert_before (&bsi, new, BSI_NEW_STMT); + + replace_phi_edge_with_variable (cond_bb, e1, phi, result); + return true; +} + +/* The function absolute_replacement does the main work of doing the absolute + replacement. Return true if the replacement is done. Otherwise return + false. + bb is the basic block where the replacement is going to be done on. arg0 + is argument 0 from the phi. Likewise for arg1. */ + +static bool +abs_replacement (basic_block cond_bb, basic_block middle_bb, + edge e0 ATTRIBUTE_UNUSED, edge e1, + tree phi, tree arg0, tree arg1) +{ + tree result; + tree new, cond; + block_stmt_iterator bsi; + edge true_edge, false_edge; + tree assign; + edge e; + tree rhs, lhs; + bool negate; + enum tree_code cond_code; + + /* If the type says honor signed zeros we cannot do this + optimization. */ + if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1)))) + return false; + + /* OTHER_BLOCK must have only one executable statement which must have the + form arg0 = -arg1 or arg1 = -arg0. */ + + assign = last_and_only_stmt (middle_bb); + /* If we did not find the proper negation assignment, then we can not + optimize. */ + if (assign == NULL) + return false; + + /* If we got here, then we have found the only executable statement + in OTHER_BLOCK. If it is anything other than arg = -arg1 or + arg1 = -arg0, then we can not optimize. */ + if (TREE_CODE (assign) != MODIFY_EXPR) + return false; + + lhs = TREE_OPERAND (assign, 0); + rhs = TREE_OPERAND (assign, 1); + + if (TREE_CODE (rhs) != NEGATE_EXPR) + return false; + + rhs = TREE_OPERAND (rhs, 0); + + /* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */ + if (!(lhs == arg0 && rhs == arg1) + && !(lhs == arg1 && rhs == arg0)) + return false; + + cond = COND_EXPR_COND (last_stmt (cond_bb)); + result = PHI_RESULT (phi); + + /* Only relationals comparing arg[01] against zero are interesting. */ + cond_code = TREE_CODE (cond); + if (cond_code != GT_EXPR && cond_code != GE_EXPR + && cond_code != LT_EXPR && cond_code != LE_EXPR) + return false; + + /* Make sure the conditional is arg[01] OP y. */ + if (TREE_OPERAND (cond, 0) != rhs) + return false; + + if (FLOAT_TYPE_P (TREE_TYPE (TREE_OPERAND (cond, 1))) + ? real_zerop (TREE_OPERAND (cond, 1)) + : integer_zerop (TREE_OPERAND (cond, 1))) + ; + else + return false; + + /* We need to know which is the true edge and which is the false + edge so that we know if have abs or negative abs. */ + extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge); + + /* For GT_EXPR/GE_EXPR, if the true edge goes to OTHER_BLOCK, then we + will need to negate the result. Similarly for LT_EXPR/LE_EXPR if + the false edge goes to OTHER_BLOCK. */ + if (cond_code == GT_EXPR || cond_code == GE_EXPR) + e = true_edge; + else + e = false_edge; + + if (e->dest == middle_bb) + negate = true; + else + negate = false; + + result = duplicate_ssa_name (result, NULL); + + if (negate) + { + tree tmp = create_tmp_var (TREE_TYPE (result), NULL); + add_referenced_var (tmp); + lhs = make_ssa_name (tmp, NULL); + } + else + lhs = result; + + /* Build the modify expression with abs expression. */ + new = build2 (MODIFY_EXPR, TREE_TYPE (lhs), + lhs, build1 (ABS_EXPR, TREE_TYPE (lhs), rhs)); + SSA_NAME_DEF_STMT (lhs) = new; + + bsi = bsi_last (cond_bb); + bsi_insert_before (&bsi, new, BSI_NEW_STMT); + + if (negate) + { + /* Get the right BSI. We want to insert after the recently + added ABS_EXPR statement (which we know is the first statement + in the block. */ + new = build2 (MODIFY_EXPR, TREE_TYPE (result), + result, build1 (NEGATE_EXPR, TREE_TYPE (lhs), lhs)); + SSA_NAME_DEF_STMT (result) = new; + + bsi_insert_after (&bsi, new, BSI_NEW_STMT); + } + + replace_phi_edge_with_variable (cond_bb, e1, phi, result); + + /* Note that we optimized this PHI. */ + return true; +} + + +/* Always do these optimizations if we have SSA + trees to work on. */ +static bool +gate_phiopt (void) +{ + return 1; +} + +struct tree_opt_pass pass_phiopt = +{ + "phiopt", /* name */ + gate_phiopt, /* gate */ + tree_ssa_phiopt, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_TREE_PHIOPT, /* tv_id */ + PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func + | TODO_ggc_collect + | TODO_verify_ssa + | TODO_verify_flow + | TODO_verify_stmts, /* todo_flags_finish */ + 0 /* letter */ +}; |
