along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
-/* This pass implements tree level if-conversion transformation of loops.
- Initial goal is to help vectorizer vectorize loops with conditions.
+/* This pass implements a tree level if-conversion of loops. Its
+ initial goal is to help the vectorizer to vectorize loops with
+ conditions.
A short description of if-conversion:
#include "tree.h"
#include "flags.h"
#include "timevar.h"
-#include "varray.h"
#include "rtl.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "tree-pass.h"
#include "target.h"
-
-/* local function prototypes */
-static unsigned int main_tree_if_conversion (void);
-static tree tree_if_convert_stmt (struct loop *loop, gimple, tree,
- gimple_stmt_iterator *);
-static void tree_if_convert_cond_stmt (struct loop *, gimple, tree,
- gimple_stmt_iterator *);
-static bool if_convertible_phi_p (struct loop *, basic_block, gimple);
-static bool if_convertible_gimple_assign_stmt_p (struct loop *, basic_block,
- gimple);
-static bool if_convertible_stmt_p (struct loop *, basic_block, gimple);
-static bool if_convertible_bb_p (struct loop *, basic_block, basic_block);
-static bool if_convertible_loop_p (struct loop *, bool);
-static void add_to_predicate_list (basic_block, tree);
-static tree add_to_dst_predicate_list (struct loop * loop, edge,
- tree, tree,
- gimple_stmt_iterator *);
-static void clean_predicate_lists (struct loop *loop);
-static basic_block find_phi_replacement_condition (struct loop *loop,
- basic_block, tree *,
- gimple_stmt_iterator *);
-static void replace_phi_with_cond_gimple_assign_stmt (gimple, tree,
- basic_block,
- gimple_stmt_iterator *);
-static void process_phi_nodes (struct loop *);
-static void combine_blocks (struct loop *);
-static gimple ifc_temp_var (tree, tree);
-static bool pred_blocks_visited_p (basic_block, bitmap *);
-static basic_block * get_loop_body_in_if_conv_order (const struct loop *loop);
-static bool bb_with_exit_edge_p (struct loop *, basic_block);
-
/* List of basic blocks in if-conversion-suitable order. */
static basic_block *ifc_bbs;
-/* Main entry point.
- Apply if-conversion to the LOOP. Return true if successful otherwise return
- false. If false is returned then loop remains unchanged.
- FOR_VECTORIZER is a boolean flag. It indicates whether if-conversion is used
- for vectorizer or not. If it is used for vectorizer, additional checks are
- used. (Vectorization checks are not yet implemented). */
+/* Make a new temp variable of type TYPE. Add GIMPLE_ASSIGN to assign EXP
+ to the new variable. */
-static bool
-tree_if_conversion (struct loop *loop, bool for_vectorizer)
+static gimple
+ifc_temp_var (tree type, tree exp)
{
- basic_block bb;
- gimple_stmt_iterator itr;
- unsigned int i;
+ const char *name = "_ifc_";
+ tree var, new_name;
+ gimple stmt;
- ifc_bbs = NULL;
+ /* Create new temporary variable. */
+ var = create_tmp_var (type, name);
+ add_referenced_var (var);
- /* if-conversion is not appropriate for all loops. First, check if loop is
- if-convertible or not. */
- if (!if_convertible_loop_p (loop, for_vectorizer))
+ /* Build new statement to assign EXP to new variable. */
+ stmt = gimple_build_assign (var, exp);
+
+ /* Get SSA name for the new variable and set make new statement
+ its definition statement. */
+ new_name = make_ssa_name (var, stmt);
+ gimple_assign_set_lhs (stmt, new_name);
+ SSA_NAME_DEF_STMT (new_name) = stmt;
+ update_stmt (stmt);
+
+ return stmt;
+}
+
+/* Add condition COND into predicate list of basic block BB. */
+
+static void
+add_to_predicate_list (basic_block bb, tree new_cond)
+{
+ tree cond = (tree) bb->aux;
+
+ if (cond)
+ cond = fold_build2_loc (EXPR_LOCATION (cond),
+ TRUTH_OR_EXPR, boolean_type_node,
+ unshare_expr (cond), new_cond);
+ else
+ cond = new_cond;
+
+ bb->aux = cond;
+}
+
+/* Add condition COND into BB's predicate list. PREV_COND is
+ existing condition. */
+
+static tree
+add_to_dst_predicate_list (struct loop *loop, edge e,
+ tree prev_cond, tree cond,
+ gimple_stmt_iterator *gsi)
+{
+ tree new_cond = NULL_TREE;
+
+ if (!flow_bb_inside_loop_p (loop, e->dest))
+ return NULL_TREE;
+
+ if (prev_cond == boolean_true_node || !prev_cond)
+ new_cond = unshare_expr (cond);
+ else
{
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file,"-------------------------\n");
- if (ifc_bbs)
- {
- free (ifc_bbs);
- ifc_bbs = NULL;
- }
- free_dominance_info (CDI_POST_DOMINATORS);
- return false;
+ tree tmp;
+ gimple tmp_stmt = NULL;
+
+ prev_cond = force_gimple_operand_gsi (gsi, unshare_expr (prev_cond),
+ true, NULL, true, GSI_SAME_STMT);
+
+ cond = force_gimple_operand_gsi (gsi, unshare_expr (cond),
+ true, NULL, true, GSI_SAME_STMT);
+
+ /* Add the condition to aux field of the edge. In case edge
+ destination is a PHI node, this condition will be ANDed with
+ block predicate to construct complete condition. */
+ e->aux = cond;
+
+ tmp = build2 (TRUTH_AND_EXPR, boolean_type_node,
+ unshare_expr (prev_cond), cond);
+ tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
+ gsi_insert_before (gsi, tmp_stmt, GSI_SAME_STMT);
+ new_cond = gimple_assign_lhs (tmp_stmt);
}
- /* Do actual work now. */
- for (i = 0; i < loop->num_nodes; i++)
- {
- tree cond;
+ add_to_predicate_list (e->dest, new_cond);
+ return new_cond;
+}
- bb = ifc_bbs [i];
+/* Return true if one of the basic block BB edge is exit of LOOP. */
- /* Update condition using predicate list. */
- cond = (tree) bb->aux;
+static bool
+bb_with_exit_edge_p (struct loop *loop, basic_block bb)
+{
+ edge e;
+ edge_iterator ei;
+ bool exit_edge_found = false;
- /* Process all statements in this basic block.
- Remove conditional expression, if any, and annotate
- destination basic block(s) appropriately. */
- for (itr = gsi_start_bb (bb); !gsi_end_p (itr); /* empty */)
- {
- gimple t = gsi_stmt (itr);
- cond = tree_if_convert_stmt (loop, t, cond, &itr);
- if (!gsi_end_p (itr))
- gsi_next (&itr);
- }
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (loop_exit_edge_p (loop, e))
+ {
+ exit_edge_found = true;
+ break;
+ }
- /* If current bb has only one successor, then consider it as an
- unconditional goto. */
- if (single_succ_p (bb))
- {
- basic_block bb_n = single_succ (bb);
+ return exit_edge_found;
+}
- /* Successor bb inherits predicate of its predecessor. If there
- is no predicate in predecessor bb, then consider successor bb
- as always executed. */
- if (cond == NULL_TREE)
- cond = boolean_true_node;
+/* STMT is a GIMPLE_COND. Update two destination's predicate list.
+ Remove COND_EXPR, if it is not the loop exit condition. Otherwise
+ update loop exit condition appropriately. GSI is the iterator
+ used to traverse statement list. STMT is part of loop LOOP. */
- add_to_predicate_list (bb_n, cond);
- }
- }
+static void
+tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
+ gimple_stmt_iterator *gsi)
+{
+ tree c2;
+ edge true_edge, false_edge;
+ location_t loc = gimple_location (stmt);
+ tree c = fold_build2_loc (loc, gimple_cond_code (stmt), boolean_type_node,
+ gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
- /* Now, all statements are if-converted and basic blocks are
- annotated appropriately. Combine all basic block into one huge
- basic block. */
- combine_blocks (loop);
+ extract_true_false_edges_from_block (gimple_bb (stmt),
+ &true_edge, &false_edge);
- /* clean up */
- clean_predicate_lists (loop);
- free (ifc_bbs);
- ifc_bbs = NULL;
+ /* Add new condition into destination's predicate list. */
- return true;
+ /* If C is true, then TRUE_EDGE is taken. */
+ add_to_dst_predicate_list (loop, true_edge, cond, c, gsi);
+
+ /* If C is false, then FALSE_EDGE is taken. */
+ c2 = invert_truthvalue_loc (loc, unshare_expr (c));
+ add_to_dst_predicate_list (loop, false_edge, cond, c2, gsi);
+
+ /* Now this conditional statement is redundant. Remove it.
+ But, do not remove exit condition! Update exit condition
+ using new condition. */
+ if (!bb_with_exit_edge_p (loop, gimple_bb (stmt)))
+ {
+ gsi_remove (gsi, true);
+ cond = NULL_TREE;
+ }
+ return;
}
-/* if-convert stmt T which is part of LOOP.
+/* If-convert stmt T which is part of LOOP.
If T is a GIMPLE_ASSIGN then it is converted into conditional modify
expression using COND. For conditional expressions, add condition in the
destination basic block's predicate list and remove conditional
- expression itself. BSI is the iterator used to traverse statements of
- loop. It is used here when it is required to delete current statement. */
+ expression itself. BSI is the iterator used to traverse statements of
+ loop. It is used here when it is required to delete current statement. */
static tree
-tree_if_convert_stmt (struct loop * loop, gimple t, tree cond,
+tree_if_convert_stmt (struct loop *loop, gimple t, tree cond,
gimple_stmt_iterator *gsi)
{
if (dump_file && (dump_flags & TDF_DETAILS))
case GIMPLE_LABEL:
break;
+ case GIMPLE_DEBUG:
+ /* ??? Should there be conditional GIMPLE_DEBUG_BINDs? */
+ if (gimple_debug_bind_p (gsi_stmt (*gsi)))
+ {
+ gimple_debug_bind_reset_value (gsi_stmt (*gsi));
+ update_stmt (gsi_stmt (*gsi));
+ }
+ break;
+
case GIMPLE_ASSIGN:
- /* This GIMPLE_ASSIGN is killing previous value of LHS. Appropriate
- value will be selected by PHI node based on condition. It is possible
+ /* This GIMPLE_ASSIGN is killing previous value of LHS. Appropriate
+ value will be selected by PHI node based on condition. It is possible
that before this transformation, PHI nodes was selecting default
- value and now it will use this new value. This is OK because it does
- not change validity the program. */
+ value and now it will use this new value. This is OK because it does
+ not change the validity of the program. */
break;
case GIMPLE_COND:
return cond;
}
-/* STMT is a GIMPLE_COND. Update two destination's predicate list.
- Remove COND_EXPR, if it is not the loop exit condition. Otherwise
- update loop exit condition appropriately. GSI is the iterator
- used to traverse statement list. STMT is part of loop LOOP. */
-
-static void
-tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
- gimple_stmt_iterator *gsi)
-{
- tree c, c2;
- edge true_edge, false_edge;
-
- gcc_assert (gimple_code (stmt) == GIMPLE_COND);
-
- c = fold_build2 (gimple_cond_code (stmt), boolean_type_node,
- gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
-
- extract_true_false_edges_from_block (gimple_bb (stmt),
- &true_edge, &false_edge);
-
- /* Add new condition into destination's predicate list. */
-
- /* If C is true then TRUE_EDGE is taken. */
- add_to_dst_predicate_list (loop, true_edge, cond, c, gsi);
-
- /* If 'c' is false then FALSE_EDGE is taken. */
- c2 = invert_truthvalue (unshare_expr (c));
- add_to_dst_predicate_list (loop, false_edge, cond, c2, gsi);
-
- /* Now this conditional statement is redundant. Remove it.
- But, do not remove exit condition! Update exit condition
- using new condition. */
- if (!bb_with_exit_edge_p (loop, gimple_bb (stmt)))
- {
- gsi_remove (gsi, true);
- cond = NULL_TREE;
- }
- return;
-}
-
-/* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
+/* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
and it belongs to basic block BB.
PHI is not if-convertible
- - if it has more than 2 arguments.
- - Virtual PHI is immediately used in another PHI node.
- - Virtual PHI on BB other than header. */
+ - if it has more than 2 arguments,
+ - virtual PHI is immediately used in another PHI node,
+ - virtual PHI on BB other than header. */
static bool
if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
return true;
}
-/* Return true, if STMT is if-convertible.
+/* Return true when STMT is if-convertible.
+
GIMPLE_ASSIGN statement is not if-convertible if,
- - It is not movable.
- - It could trap.
+ - it is not movable,
+ - it could trap,
- LHS is not var decl.
- GIMPLE_ASSIGN is part of block BB, which is inside loop LOOP. */
+ GIMPLE_ASSIGN is part of block BB, which is inside loop LOOP. */
static bool
if_convertible_gimple_assign_stmt_p (struct loop *loop, basic_block bb,
gimple stmt)
{
- tree lhs;
-
- if (!is_gimple_assign (stmt))
- return false;
+ tree lhs = gimple_assign_lhs (stmt);
if (dump_file && (dump_flags & TDF_DETAILS))
{
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
- lhs = gimple_assign_lhs (stmt);
-
/* Some of these constrains might be too conservative. */
if (stmt_ends_bb_p (stmt)
|| gimple_has_volatile_ops (stmt)
/* Return true, iff STMT is if-convertible.
Statement is if-convertible if,
- - It is if-convertible GIMPLE_ASSGIN
- - It is GIMPLE_LABEL or GIMPLE_COND.
+ - it is if-convertible GIMPLE_ASSGIN,
+ - it is GIMPLE_LABEL or GIMPLE_COND.
STMT is inside block BB, which is inside loop LOOP. */
static bool
switch (gimple_code (stmt))
{
case GIMPLE_LABEL:
- break;
+ case GIMPLE_DEBUG:
+ case GIMPLE_COND:
+ return true;
case GIMPLE_ASSIGN:
-
- if (!if_convertible_gimple_assign_stmt_p (loop, bb, stmt))
- return false;
- break;
-
- case GIMPLE_COND:
- break;
+ return if_convertible_gimple_assign_stmt_p (loop, bb, stmt);
default:
/* Don't know what to do with 'em so don't do anything. */
/* Return true, iff BB is if-convertible.
Note: This routine does _not_ check basic block statements and phis.
- Basic block is not if-convertible if,
- - Basic block is non-empty and it is after exit block (in BFS order).
- - Basic block is after exit block but before latch.
- - Basic block edge(s) is not normal.
+ Basic block is not if-convertible if:
+ - basic block is non-empty and it is after exit block (in BFS order),
+ - basic block is after exit block but before latch,
+ - basic block edge(s) is not normal.
EXIT_BB_SEEN is true if basic block with exit edge is already seen.
BB is inside loop LOOP. */
{
if (bb != loop->latch)
{
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "basic block after exit bb but before latch\n");
- return false;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "basic block after exit bb but before latch\n");
+ return false;
+ }
+ else if (!empty_block_p (bb))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "non empty basic block after exit bb\n");
+ return false;
+ }
+ else if (bb == loop->latch
+ && bb != exit_bb
+ && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "latch is not dominated by exit_block\n");
+ return false;
+ }
+ }
+
+ /* Be less adventurous and handle only normal edges. */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->flags &
+ (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,"Difficult to handle edges\n");
+ return false;
+ }
+
+ return true;
+}
+
+/* Return TRUE iff, all pred blocks of BB are visited.
+ Bitmap VISITED keeps history of visited blocks. */
+
+static bool
+pred_blocks_visited_p (basic_block bb, bitmap *visited)
+{
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (!bitmap_bit_p (*visited, e->src->index))
+ return false;
+
+ return true;
+}
+
+/* Get body of a LOOP in suitable order for if-conversion. It is
+ caller's responsibility to deallocate basic block list.
+ If-conversion suitable order is, breadth first sort (BFS) order
+ with an additional constraint: select a block only if all its
+ predecessors are already selected. */
+
+static basic_block *
+get_loop_body_in_if_conv_order (const struct loop *loop)
+{
+ basic_block *blocks, *blocks_in_bfs_order;
+ basic_block bb;
+ bitmap visited;
+ unsigned int index = 0;
+ unsigned int visited_count = 0;
+
+ gcc_assert (loop->num_nodes);
+ gcc_assert (loop->latch != EXIT_BLOCK_PTR);
+
+ blocks = XCNEWVEC (basic_block, loop->num_nodes);
+ visited = BITMAP_ALLOC (NULL);
+
+ blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
+
+ index = 0;
+ while (index < loop->num_nodes)
+ {
+ bb = blocks_in_bfs_order [index];
+
+ if (bb->flags & BB_IRREDUCIBLE_LOOP)
+ {
+ free (blocks_in_bfs_order);
+ BITMAP_FREE (visited);
+ free (blocks);
+ return NULL;
+ }
+
+ if (!bitmap_bit_p (visited, bb->index))
+ {
+ if (pred_blocks_visited_p (bb, &visited)
+ || bb == loop->header)
+ {
+ /* This block is now visited. */
+ bitmap_set_bit (visited, bb->index);
+ blocks[visited_count++] = bb;
+ }
+ }
+
+ index++;
+
+ if (index == loop->num_nodes
+ && visited_count != loop->num_nodes)
+ /* Not done yet. */
+ index = 0;
+ }
+ free (blocks_in_bfs_order);
+ BITMAP_FREE (visited);
+ return blocks;
+}
+
+/* Return true, iff LOOP is if-convertible.
+ LOOP is if-convertible if:
+ - it is innermost,
+ - it has two or more basic blocks,
+ - it has only one exit,
+ - loop header is not the exit edge,
+ - if its basic blocks and phi nodes are if convertible. See above for
+ more info.
+ FOR_VECTORIZER enables vectorizer specific checks, for example, support
+ for vector conditions, data dependency checks, etc.
+ (Not implemented yet). */
+
+static bool
+pred_blocks_visited_p (basic_block bb, bitmap *visited)
+{
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (!bitmap_bit_p (*visited, e->src->index))
+ return false;
+
+ return true;
+}
+
+/* Get body of a LOOP in suitable order for if-conversion. It is
+ caller's responsibility to deallocate basic block list.
+ If-conversion suitable order is, breadth first sort (BFS) order
+ with an additional constraint: select a block only if all its
+ predecessors are already selected. */
+
+static basic_block *
+get_loop_body_in_if_conv_order (const struct loop *loop)
+{
+ basic_block *blocks, *blocks_in_bfs_order;
+ basic_block bb;
+ bitmap visited;
+ unsigned int index = 0;
+ unsigned int visited_count = 0;
+
+ gcc_assert (loop->num_nodes);
+ gcc_assert (loop->latch != EXIT_BLOCK_PTR);
+
+ blocks = XCNEWVEC (basic_block, loop->num_nodes);
+ visited = BITMAP_ALLOC (NULL);
+
+ blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
+
+ index = 0;
+ while (index < loop->num_nodes)
+ {
+ bb = blocks_in_bfs_order [index];
+
+ if (bb->flags & BB_IRREDUCIBLE_LOOP)
+ {
+ free (blocks_in_bfs_order);
+ BITMAP_FREE (visited);
+ free (blocks);
+ return NULL;
}
- else if (!empty_block_p (bb))
+
+ if (!bitmap_bit_p (visited, bb->index))
{
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "non empty basic block after exit bb\n");
- return false;
+ if (pred_blocks_visited_p (bb, &visited)
+ || bb == loop->header)
+ {
+ /* This block is now visited. */
+ bitmap_set_bit (visited, bb->index);
+ blocks[visited_count++] = bb;
+ }
}
- else if (bb == loop->latch
- && bb != exit_bb
- && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "latch is not dominated by exit_block\n");
- return false;
- }
- }
- /* Be less adventurous and handle only normal edges. */
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (e->flags &
- (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file,"Difficult to handle edges\n");
- return false;
- }
+ index++;
- return true;
+ if (index == loop->num_nodes
+ && visited_count != loop->num_nodes)
+ /* Not done yet. */
+ index = 0;
+ }
+ free (blocks_in_bfs_order);
+ BITMAP_FREE (visited);
+ return blocks;
}
-/* Return true, iff LOOP is if-convertible.
- LOOP is if-convertible if,
- - It is innermost.
- - It has two or more basic blocks.
- - It has only one exit.
- - Loop header is not the exit edge.
- - If its basic blocks and phi nodes are if convertible. See above for
- more info.
- FOR_VECTORIZER enables vectorizer specific checks. For example, support
- for vector conditions, data dependency checks etc.. (Not implemented yet). */
+/* Return true when LOOP is if-convertible.
+ LOOP is if-convertible if:
+ - it is innermost,
+ - it has two or more basic blocks,
+ - it has only one exit,
+ - loop header is not the exit edge,
+ - if its basic blocks and phi nodes are if convertible. */
static bool
-if_convertible_loop_p (struct loop *loop, bool for_vectorizer ATTRIBUTE_UNUSED)
+if_convertible_loop_p (struct loop *loop)
{
basic_block bb;
gimple_stmt_iterator itr;
if (!if_convertible_bb_p (loop, bb, exit_bb))
return false;
- /* Check statements. */
for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
if (!if_convertible_stmt_p (loop, bb, gsi_stmt (itr)))
return false;
- /* ??? Check data dependency for vectorizer. */
- /* What about phi nodes ? */
itr = gsi_start_phis (bb);
- /* Clear aux field of incoming edges to a bb with a phi node. */
if (!gsi_end_p (itr))
FOR_EACH_EDGE (e, ei, bb->preds)
e->aux = NULL;
- /* Check statements. */
for (; !gsi_end_p (itr); gsi_next (&itr))
if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
return false;
exit_bb = bb;
}
- /* OK. Did not find any potential issues so go ahead in if-convert
- this loop. Now there is no looking back. */
if (dump_file)
fprintf (dump_file,"Applying if-conversion\n");
return true;
}
-/* Add condition COND into predicate list of basic block BB. */
-
-static void
-add_to_predicate_list (basic_block bb, tree new_cond)
-{
- tree cond = (tree) bb->aux;
-
- if (cond)
- cond = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- unshare_expr (cond), new_cond);
- else
- cond = new_cond;
-
- bb->aux = cond;
-}
-
-/* Add condition COND into BB's predicate list. PREV_COND is
- existing condition. */
-
-static tree
-add_to_dst_predicate_list (struct loop * loop, edge e,
- tree prev_cond, tree cond,
- gimple_stmt_iterator *gsi)
-{
- tree new_cond = NULL_TREE;
-
- if (!flow_bb_inside_loop_p (loop, e->dest))
- return NULL_TREE;
-
- if (prev_cond == boolean_true_node || !prev_cond)
- new_cond = unshare_expr (cond);
- else
- {
- tree tmp;
- gimple tmp_stmt = NULL;
-
- prev_cond = force_gimple_operand_gsi (gsi, unshare_expr (prev_cond),
- true, NULL, true, GSI_SAME_STMT);
-
- cond = force_gimple_operand_gsi (gsi, unshare_expr (cond),
- true, NULL, true, GSI_SAME_STMT);
-
- /* Add the condition to aux field of the edge. In case edge
- destination is a PHI node, this condition will be ANDed with
- block predicate to construct complete condition. */
- e->aux = cond;
-
- /* new_cond == prev_cond AND cond */
- tmp = build2 (TRUTH_AND_EXPR, boolean_type_node,
- unshare_expr (prev_cond), cond);
- tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
- gsi_insert_before (gsi, tmp_stmt, GSI_SAME_STMT);
- new_cond = gimple_assign_lhs (tmp_stmt);
- }
- add_to_predicate_list (e->dest, new_cond);
- return new_cond;
-}
-
/* During if-conversion aux field from basic block structure is used to hold
- predicate list. Clean each basic block's predicate list for the given LOOP.
+ predicate list. Clean each basic block's predicate list for the given LOOP.
Also clean aux field of successor edges, used to hold true and false
condition from conditional expression. */
}
/* Basic block BB has two predecessors. Using predecessor's aux field, set
- appropriate condition COND for the PHI node replacement. Return true block
+ appropriate condition COND for the PHI node replacement. Return true block
whose phi arguments are selected when cond is true. */
static basic_block
-find_phi_replacement_condition (struct loop *loop,
+find_phi_replacement_condition (struct loop *loop,
basic_block bb, tree *cond,
gimple_stmt_iterator *gsi)
{
S2: x = c ? b : a;
S2 is preferred over S1. Make 'b' first_bb and use its condition.
-
+
2) Do not make loop header first_bb.
3)
S3: x = (c == d) ? b : a;
- S3 is preferred over S1 and S2*, Make 'b' first_bb and use
+ S3 is preferred over S1 and S2*, Make 'b' first_bb and use
its condition.
4) If pred B is dominated by pred A then use pred B's condition.
{
*cond = (tree) (second_edge->src)->aux;
- /* If there is a condition on an incoming edge,
- AND it with the incoming bb predicate. */
+ /* If there is a condition on an incoming edge, add it to the
+ incoming bb predicate. */
if (second_edge->aux)
*cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
*cond, (tree) second_edge->aux);
if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
- /* We can be smart here and choose inverted
- condition without switching bbs. */
*cond = invert_truthvalue (*cond);
else
/* Select non loop header bb. */
}
else
{
- /* FIRST_BB is not loop header */
*cond = (tree) (first_edge->src)->aux;
- /* If there is a condition on an incoming edge,
- AND it with the incoming bb predicate. */
+ /* If there is a condition on an incoming edge, add it to the
+ incoming bb predicate. */
if (first_edge->aux)
*cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
*cond, (tree) first_edge->aux);
}
- /* Create temp. for the condition. Vectorizer prefers to have gimple
- value as condition. Various targets use different means to communicate
- condition in vector compare operation. Using gimple value allows
- compiler to emit vector compare and select RTL without exposing
- compare's result. */
+ /* Gimplify the condition: the vectorizer prefers to have gimple
+ values as conditions. Various targets use different means to
+ communicate conditions in vector compare operations. Using a
+ gimple value allows the compiler to emit vector compare and
+ select RTL without exposing compare's result. */
*cond = force_gimple_operand_gsi (gsi, unshare_expr (*cond),
false, NULL_TREE,
true, GSI_SAME_STMT);
return first_edge->src;
}
+/* Replace PHI node with conditional modify expr using COND. This
+ routine does not handle PHI nodes with more than two arguments.
-/* Replace PHI node with conditional modify expr using COND.
- This routine does not handle PHI nodes with more than two arguments.
For example,
S1: A = PHI <x1(1), x2(5)
is converted into,
S2: A = cond ? x1 : x2;
- S2 is inserted at the top of basic block's statement list.
- When COND is true, phi arg from TRUE_BB is selected.
-*/
+
+ The generated code is inserted at GSI that points to the top of
+ basic block's statement list. When COND is true, phi arg from
+ TRUE_BB is selected. */
static void
replace_phi_with_cond_gimple_assign_stmt (gimple phi, tree cond,
tree rhs;
tree arg_0, arg_1;
- gcc_assert (gimple_code (phi) == GIMPLE_PHI);
-
- /* If this is not filtered earlier, then now it is too late. */
- gcc_assert (gimple_phi_num_args (phi) == 2);
+ gcc_assert (gimple_code (phi) == GIMPLE_PHI
+ && gimple_phi_num_args (phi) == 2);
- /* Find basic block and initialize iterator. */
bb = gimple_bb (phi);
/* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
unshare_expr (cond), unshare_expr (arg_0),
unshare_expr (arg_1));
- /* Create new GIMPLE_ASSIGN statement using RHS. */
new_stmt = gimple_build_assign (unshare_expr (PHI_RESULT (phi)), rhs);
-
- /* Make new statement definition of the original phi result. */
SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
-
- /* Insert using iterator. */
gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
update_stmt (new_stmt);
}
}
-/* Process phi nodes for the given LOOP. Replace phi nodes with cond
- modify expr. */
+/* Process phi nodes for the given LOOP. Replace phi nodes with
+ conditional modify expressions. */
static void
process_phi_nodes (struct loop *loop)
unsigned int orig_loop_num_nodes = loop->num_nodes;
unsigned int i;
- /* Replace phi nodes with cond. modify expr. */
for (i = 1; i < orig_loop_num_nodes; i++)
{
gimple phi;
phi_gsi = gsi_start_phis (bb);
gsi = gsi_after_labels (bb);
- /* BB has two predecessors. Using predecessor's aux field, set
+ /* BB has two predecessors. Using predecessor's aux field, set
appropriate condition for the PHI node replacement. */
if (!gsi_end_p (phi_gsi))
true_bb = find_phi_replacement_condition (loop, bb, &cond, &gsi);
}
set_phi_nodes (bb, NULL);
}
- return;
}
-/* Combine all basic block from the given LOOP into one or two super
- basic block. Replace PHI nodes with conditional modify expression. */
+/* Combine all the basic blocks from LOOP into one or two super basic
+ blocks. Replace PHI nodes with conditional modify expressions. */
static void
combine_blocks (struct loop *loop)
/* Process phi nodes to prepare blocks for merge. */
process_phi_nodes (loop);
- /* Merge basic blocks. First remove all the edges in the loop, except
- for those from the exit block. */
+ /* Merge basic blocks: first remove all the edges in the loop,
+ except for those from the exit block. */
exit_bb = NULL;
for (i = 0; i < orig_loop_num_nodes; i++)
{
{
if (exit_bb != loop->header)
{
- /* Connect this node with loop header. */
+ /* Connect this node to loop header. */
make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
}
}
else
{
- /* If the loop does not have exit then reconnect header and latch. */
+ /* If the loop does not have an exit, reconnect header and latch. */
make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
}
}
/* Now if possible, merge loop header and block with exit edge.
- This reduces number of basic blocks to 2. Auto vectorizer addresses
+ This reduces number of basic blocks to 2. Auto vectorizer addresses
loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
if (exit_bb
&& exit_bb != loop->header
merge_blocks (loop->header, exit_bb);
}
-/* Make a new temp variable of type TYPE. Add GIMPLE_ASSIGN to assign EXP
- to the new variable. */
-
-static gimple
-ifc_temp_var (tree type, tree exp)
-{
- const char *name = "_ifc_";
- tree var, new_name;
- gimple stmt;
-
- /* Create new temporary variable. */
- var = create_tmp_var (type, name);
- add_referenced_var (var);
-
- /* Build new statement to assign EXP to new variable. */
- stmt = gimple_build_assign (var, exp);
-
- /* Get SSA name for the new variable and set make new statement
- its definition statement. */
- new_name = make_ssa_name (var, stmt);
- gimple_assign_set_lhs (stmt, new_name);
- SSA_NAME_DEF_STMT (new_name) = stmt;
- update_stmt (stmt);
-
- return stmt;
-}
-
-
-/* Return TRUE iff, all pred blocks of BB are visited.
- Bitmap VISITED keeps history of visited blocks. */
+/* Main entry point. Apply if-conversion to the LOOP. Return true if
+ successful otherwise return false. If false is returned then loop
+ remains unchanged. FOR_VECTORIZER is a boolean flag. It indicates
+ whether if-conversion is used for vectorizer or not. If it is used
+ for vectorizer, additional checks are used. (Vectorization checks
+ are not yet implemented). */
static bool
-pred_blocks_visited_p (basic_block bb, bitmap *visited)
-{
- edge e;
- edge_iterator ei;
- FOR_EACH_EDGE (e, ei, bb->preds)
- if (!bitmap_bit_p (*visited, e->src->index))
- return false;
-
- return true;
-}
-
-/* Get body of a LOOP in suitable order for if-conversion.
- It is caller's responsibility to deallocate basic block
- list. If-conversion suitable order is, BFS order with one
- additional constraint. Select block in BFS block, if all
- pred are already selected. */
-
-static basic_block *
-get_loop_body_in_if_conv_order (const struct loop *loop)
+tree_if_conversion (struct loop *loop, bool for_vectorizer)
{
- basic_block *blocks, *blocks_in_bfs_order;
basic_block bb;
- bitmap visited;
- unsigned int index = 0;
- unsigned int visited_count = 0;
-
- gcc_assert (loop->num_nodes);
- gcc_assert (loop->latch != EXIT_BLOCK_PTR);
-
- blocks = XCNEWVEC (basic_block, loop->num_nodes);
- visited = BITMAP_ALLOC (NULL);
+ gimple_stmt_iterator itr;
+ unsigned int i;
- blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
+ ifc_bbs = NULL;
- index = 0;
- while (index < loop->num_nodes)
+ /* If-conversion is not appropriate for all loops. First, check if
+ loop is if-convertible or not. */
+ if (!if_convertible_loop_p (loop, for_vectorizer))
{
- bb = blocks_in_bfs_order [index];
-
- if (bb->flags & BB_IRREDUCIBLE_LOOP)
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,"-------------------------\n");
+ if (ifc_bbs)
{
- free (blocks_in_bfs_order);
- BITMAP_FREE (visited);
- free (blocks);
- return NULL;
+ free (ifc_bbs);
+ ifc_bbs = NULL;
}
- if (!bitmap_bit_p (visited, bb->index))
+ free_dominance_info (CDI_POST_DOMINATORS);
+ return false;
+ }
+
+ /* Do actual work now. */
+ for (i = 0; i < loop->num_nodes; i++)
+ {
+ tree cond;
+
+ bb = ifc_bbs [i];
+
+ /* Update condition using predicate list. */
+ cond = (tree) bb->aux;
+
+ /* Process all statements in this basic block.
+ Remove conditional expression, if any, and annotate
+ destination basic block(s) appropriately. */
+ for (itr = gsi_start_bb (bb); !gsi_end_p (itr); /* empty */)
{
- if (pred_blocks_visited_p (bb, &visited)
- || bb == loop->header)
- {
- /* This block is now visited. */
- bitmap_set_bit (visited, bb->index);
- blocks[visited_count++] = bb;
- }
+ gimple t = gsi_stmt (itr);
+ cond = tree_if_convert_stmt (loop, t, cond, &itr);
+ if (!gsi_end_p (itr))
+ gsi_next (&itr);
}
- index++;
- if (index == loop->num_nodes
- && visited_count != loop->num_nodes)
+
+ /* If current bb has only one successor, then consider it as an
+ unconditional goto. */
+ if (single_succ_p (bb))
{
- /* Not done yet. */
- index = 0;
+ basic_block bb_n = single_succ (bb);
+
+ /* Successor bb inherits predicate of its predecessor. If there
+ is no predicate in predecessor bb, then consider successor bb
+ as always executed. */
+ if (cond == NULL_TREE)
+ cond = boolean_true_node;
+
+ add_to_predicate_list (bb_n, cond);
}
}
- free (blocks_in_bfs_order);
- BITMAP_FREE (visited);
- return blocks;
-}
-
-/* Return true if one of the basic block BB edge is exit of LOOP. */
-static bool
-bb_with_exit_edge_p (struct loop *loop, basic_block bb)
-{
- edge e;
- edge_iterator ei;
- bool exit_edge_found = false;
+ /* Now, all statements are if-converted and basic blocks are
+ annotated appropriately. Combine all basic block into one huge
+ basic block. */
+ combine_blocks (loop);
- FOR_EACH_EDGE (e, ei, bb->succs)
- if (loop_exit_edge_p (loop, e))
- {
- exit_edge_found = true;
- break;
- }
+ /* clean up */
+ clean_predicate_lists (loop);
+ free (ifc_bbs);
+ ifc_bbs = NULL;
- return exit_edge_found;
+ return true;
}
/* Tree if-conversion pass management. */
return 0;
FOR_EACH_LOOP (li, loop, 0)
- {
- tree_if_conversion (loop, true);
- }
+ tree_if_conversion (loop);
+
return 0;
}
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_loops | TODO_verify_stmts | TODO_verify_flow
+ TODO_dump_func | TODO_verify_stmts | TODO_verify_flow
/* todo_flags_finish */
}
};
OSDN Git Service
