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"
/* List of basic blocks in if-conversion-suitable order. */
static basic_block *ifc_bbs;
-/* Make a new temp variable of type TYPE. Add GIMPLE_ASSIGN to assign EXP
- to the new variable. */
+/* 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 gimple
ifc_temp_var (tree type, tree exp)
SSA_NAME_DEF_STMT (new_name) = stmt;
update_stmt (stmt);
- return stmt;
-}
-
-/* Add condition NEW_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;
-}
-
-/* And condition COND to the previous condition PREV_COND and add this
- to the predicate list of the destination of edge E. GSI is the
- place where the gimplification of the resulting condition should
- output code. LOOP is the loop to be if-converted. */
-
-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-conversion is not appropriate for all loops. First, check if
+ loop is if-convertible or not. */
+ if (!if_convertible_loop_p (loop, for_vectorizer))
{
tree tmp;
gimple tmp_stmt = NULL;
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. */
+ /* Add the condition COND to the e->aux field. In case the edge
+ destination is a PHI node, this condition will be added to
+ the block predicate to construct a complete condition. */
e->aux = cond;
tmp = build2 (TRUTH_AND_EXPR, boolean_type_node,
return new_cond;
}
-/* Return true if one of the basic block BB edge is exit of LOOP. */
+/* Return true if one of the successor edges of BB exits LOOP. */
static bool
bb_with_exit_edge_p (struct loop *loop, basic_block bb)
{
edge e;
edge_iterator ei;
- bool exit_edge_found = false;
FOR_EACH_EDGE (e, ei, bb->succs)
if (loop_exit_edge_p (loop, e))
- {
- exit_edge_found = true;
- break;
- }
+ return true;
- return exit_edge_found;
+ return false;
}
-/* 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. */
+ /* 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;
static void
tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
tree c = fold_build2_loc (loc, 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);
+ /* Now, all statements are if-converted and basic blocks are
+ annotated appropriately. Combine all basic block into one huge
+ basic block. */
+ combine_blocks (loop);
/* Add new condition into destination's predicate list. */
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. */
+ /* Now this conditional statement is redundant. Remove it. But, do
+ not remove the exit condition! Update the exit condition using
+ the 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.
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;
+ location_t loc = gimple_location (stmt);
+
+ gcc_assert (gimple_code (stmt) == GIMPLE_COND);
+
+ c = fold_build2_loc (loc, 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_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;
+}
+
/* 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
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,
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)
switch (gimple_code (stmt))
{
case GIMPLE_LABEL:
- break;
-
case GIMPLE_DEBUG:
- break;
+ 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. */
(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");
+ 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. */
+/* 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)
return blocks;
}
-/* Return true, iff LOOP is if-convertible.
+/* Return true when LOOP is if-convertible.
LOOP is if-convertible if:
- it is innermost,
- it has two or more basic blocks,
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_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
+ {
+ 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.
Also clean aux field of successor edges, used to hold true and false
{
*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);
+ gcc_assert (gimple_code (phi) == GIMPLE_PHI
+ && gimple_phi_num_args (phi) == 2);
- /* If this is not filtered earlier, then now it is too late. */
- gcc_assert (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);
}
set_phi_nodes (bb, NULL);
}
- return;
}
/* Combine all the basic blocks from LOOP into one or two super basic
/* 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);
}
merge_blocks (loop->header, exit_bb);
}
-/* Main entry point. Apply if-conversion to the LOOP. Return true if
- successful otherwise return false. If false is returned then loop
- remains unchanged. */
+/* 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. */
static bool
tree_if_conversion (struct loop *loop)
{
+ 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;
- gimple_stmt_iterator itr;
- unsigned int i;
+ 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);
ifc_bbs = NULL;
/* If-conversion is not appropriate for all loops. First, check if
- loop is if-convertible or not. */
+ the loop is if-convertible. */
if (!if_convertible_loop_p (loop))
{
if (dump_file && (dump_flags & TDF_DETAILS))
free (ifc_bbs);
ifc_bbs = NULL;
}
- 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 (!bitmap_bit_p (visited, bb->index))
{
gimple t = gsi_stmt (itr);
cond = tree_if_convert_stmt (loop, t, cond, &itr);
gsi_next (&itr);
}
- /* 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);
-
- /* 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;
+ index++;
- add_to_predicate_list (bb_n, cond);
- }
+ if (index == loop->num_nodes
+ && visited_count != loop->num_nodes)
+ /* Not done yet. */
+ index = 0;
}
/* Now, all statements are if-converted and basic blocks are
- annotated appropriately. Combine all basic block into one huge
- basic block. */
+ annotated appropriately. Combine all the basic blocks into one
+ huge basic block. */
combine_blocks (loop);
/* clean up */