/* 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
+/* Create a new temp variable of type TYPE. Add GIMPLE_ASSIGN to assign EXP
to the new variable. */
static gimple
return stmt;
}
-/* Add condition COND into predicate list of basic block BB. */
+/* Add condition NEW_COND to the predicate list of basic block BB. */
static void
add_to_predicate_list (basic_block bb, tree new_cond)
if (cond)
cond = fold_build2_loc (EXPR_LOCATION (cond),
- TRUTH_OR_EXPR, boolean_type_node,
- unshare_expr (cond), new_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. */
+/* Add the 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,
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. */
+ Remove COND_EXPR, if it is not the exit condition of LOOP.
+ Otherwise update the exit condition of LOOP appropriately. GSI
+ points to the statement STMT. */
static void
tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
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.
- 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. */
+
+ If T is a GIMPLE_ASSIGN then it is converted into a conditional
+ modify expression using COND. For conditional expressions, add
+ a condition in the destination basic block's predicate list and
+ remove the conditional expression itself. GSI points to the
+ statement T. */
static tree
tree_if_convert_stmt (struct loop *loop, gimple t, tree cond,
default:
gcc_unreachable ();
}
+
return cond;
}
-/* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
+/* Return true when 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,
+
+ 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. */
- it is not movable,
- it could trap,
- LHS is not var decl.
+
GIMPLE_ASSIGN is part of block BB, which is inside loop LOOP. */
static bool
return true;
}
-/* 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.
- STMT is inside block BB, which is inside loop LOOP. */
+/* Return true when STMT is if-convertible.
+
+ A statement is if-convertible if:
+ - it is an if-convertible GIMPLE_ASSGIN,
+ - it is a GIMPLE_LABEL or a GIMPLE_COND.
+
+ STMT is inside BB, which is inside loop LOOP. */
static bool
if_convertible_stmt_p (struct loop *loop, basic_block bb, gimple stmt)
return true;
}
-/* 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.
- EXIT_BB_SEEN is true if basic block with exit edge is already seen.
- BB is inside loop LOOP. */
+/* Return true when BB is if-convertible. This routine does not check
+ basic block's statements and phis.
+
+ A basic block is not if-convertible if:
+ - it is non-empty and it is after the exit block (in BFS order),
+ - it is after the exit block but before the latch,
+ - its edges are not normal.
+
+ EXIT_BB is the basic block containing the exit of the LOOP. BB is
+ inside LOOP. */
static bool
if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
(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. */
-
-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). */
+/* Return true when all predecessor blocks of BB are visited. The
+ VISITED bitmap keeps track of the visited blocks. */
static bool
pred_blocks_visited_p (basic_block bb, bitmap *visited)
return true;
}
-/* 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
- condition from conditional expression. */
+/* During if-conversion, the bb->aux field is used to hold a predicate
+ list. This function cleans for all the basic blocks in the given
+ LOOP their predicate list. It also cleans up the e->aux field of
+ all the successor edges: e->aux is used to hold the true and false
+ conditions for conditional expressions. */
static void
clean_predicate_lists (struct loop *loop)
free (bb);
}
-/* Basic block BB has two predecessors. Using predecessor's aux field, set
- appropriate condition COND for the PHI node replacement. Return true block
- whose phi arguments are selected when cond is true. */
+/* Basic block BB has two predecessors. Using predecessor's bb->aux
+ field, set appropriate condition COND for the PHI node replacement.
+ Return true block whose phi arguments are selected when cond is
+ true. LOOP is the loop containing the if-converted region, GSI is
+ the place to insert the code for the if-conversion. */
static basic_block
find_phi_replacement_condition (struct loop *loop,
delete_basic_block (bb);
}
- /* Now if possible, merge loop header and block with exit edge.
- This reduces number of basic blocks to 2. Auto vectorizer addresses
- loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
+ /* If possible, merge loop header to the block with the exit edge.
+ This reduces the number of basic blocks to two, to please the
+ vectorizer that handles only loops with two nodes.
+
+ FIXME: Call cleanup_tree_cfg. */
if (exit_bb
&& exit_bb != loop->header
&& can_merge_blocks_p (loop->header, exit_bb))
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. 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). */
+/* Main entry point: return true when LOOP is if-converted, otherwise
+ the loop remains unchanged. */
static bool
-tree_if_conversion (struct loop *loop, bool for_vectorizer)
+tree_if_conversion (struct loop *loop)
{
- basic_block bb;
gimple_stmt_iterator itr;
unsigned int i;
ifc_bbs = NULL;
/* 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))
+ the loop is if-convertible. */
+ if (!if_convertible_loop_p (loop))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,"-------------------------\n");
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;
+ basic_block bb = ifc_bbs [i];
+ tree cond = (tree) bb->aux;
- /* Process all statements in this basic block.
+ /* Process all the 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 */)
{
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. */
+ /* The successor bb inherits the predicate of its
+ predecessor. If there is no predicate in the predecessor
+ bb, then consider the successor bb as always executed. */
if (cond == NULL_TREE)
cond = boolean_true_node;
}
/* 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 */
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