/* Dead code elimination pass for the GNU compiler.
- Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ Free Software Foundation, Inc.
Contributed by Ben Elliston <bje@redhat.com>
and Andrew MacLeod <amacleod@redhat.com>
Adapted to use control dependence by Steven Bosscher, SUSE Labs.
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
+Free Software Foundation; either version 3, or (at your option) any
later version.
GCC is distributed in the hope that it will be useful, but WITHOUT
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, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
/* Dead code elimination.
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "errors.h"
#include "ggc.h"
/* These RTL headers are needed for basic-block.h. */
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
+#include "obstack.h"
#include "basic-block.h"
#include "tree.h"
#include "diagnostic.h"
#include "tree-flow.h"
-#include "tree-gimple.h"
+#include "gimple.h"
#include "tree-dump.h"
#include "tree-pass.h"
#include "timevar.h"
#include "flags.h"
-\f
+#include "cfgloop.h"
+#include "tree-scalar-evolution.h"
+
static struct stmt_stats
{
int total;
int removed_phis;
} stats;
-static varray_type worklist;
+#define STMT_NECESSARY GF_PLF_1
+
+static VEC(gimple,heap) *worklist;
/* Vector indicating an SSA name has already been processed and marked
as necessary. */
use a bitmap for each block recording its edges. An array holds the
bitmap. The Ith bit in the bitmap is set if that block is dependent
on the Ith edge. */
-bitmap *control_dependence_map;
-
-/* Execute CODE for each edge (given number EDGE_NUMBER within the CODE)
- for which the block with index N is control dependent. */
-#define EXECUTE_IF_CONTROL_DEPENDENT(N, EDGE_NUMBER, CODE) \
- { \
- bitmap_iterator bi; \
- \
- EXECUTE_IF_SET_IN_BITMAP (control_dependence_map[N], 0, EDGE_NUMBER, bi) \
- { \
- CODE; \
- } \
- }
-
-/* Local function prototypes. */
-static inline void set_control_dependence_map_bit (basic_block, int);
-static inline void clear_control_dependence_bitmap (basic_block);
-static void find_all_control_dependences (struct edge_list *);
-static void find_control_dependence (struct edge_list *, int);
-static inline basic_block find_pdom (basic_block);
-
-static inline void mark_stmt_necessary (tree, bool);
-static inline void mark_operand_necessary (tree, bool);
-
-static void mark_stmt_if_obviously_necessary (tree, bool);
-static void find_obviously_necessary_stmts (struct edge_list *);
-
-static void mark_control_dependent_edges_necessary (basic_block, struct edge_list *);
-static void propagate_necessity (struct edge_list *);
-
-static void eliminate_unnecessary_stmts (void);
-static void remove_dead_phis (basic_block);
-static void remove_dead_stmt (block_stmt_iterator *, basic_block);
-
-static void print_stats (void);
-static void tree_dce_init (bool);
-static void tree_dce_done (bool);
-\f
+static bitmap *control_dependence_map;
+
+/* Vector indicating that a basic block has already had all the edges
+ processed that it is control dependent on. */
+static sbitmap visited_control_parents;
+
+/* TRUE if this pass alters the CFG (by removing control statements).
+ FALSE otherwise.
+
+ If this pass alters the CFG, then it will arrange for the dominators
+ to be recomputed. */
+static bool cfg_altered;
+
+/* Execute code that follows the macro for each edge (given number
+ EDGE_NUMBER within the CODE) for which the block with index N is
+ control dependent. */
+#define EXECUTE_IF_CONTROL_DEPENDENT(BI, N, EDGE_NUMBER) \
+ EXECUTE_IF_SET_IN_BITMAP (control_dependence_map[(N)], 0, \
+ (EDGE_NUMBER), (BI))
+
+
/* Indicate block BB is control dependent on an edge with index EDGE_INDEX. */
static inline void
set_control_dependence_map_bit (basic_block bb, int edge_index)
}
/* Clear all control dependences for block BB. */
-static inline
-void clear_control_dependence_bitmap (basic_block bb)
+static inline void
+clear_control_dependence_bitmap (basic_block bb)
{
bitmap_clear (control_dependence_map[bb->index]);
}
-/* Record all blocks' control dependences on all edges in the edge
- list EL, ala Morgan, Section 3.6. */
-static void
-find_all_control_dependences (struct edge_list *el)
+/* Find the immediate postdominator PDOM of the specified basic block BLOCK.
+ This function is necessary because some blocks have negative numbers. */
+
+static inline basic_block
+find_pdom (basic_block block)
{
- int i;
+ gcc_assert (block != ENTRY_BLOCK_PTR);
- for (i = 0; i < NUM_EDGES (el); ++i)
- find_control_dependence (el, i);
+ if (block == EXIT_BLOCK_PTR)
+ return EXIT_BLOCK_PTR;
+ else
+ {
+ basic_block bb = get_immediate_dominator (CDI_POST_DOMINATORS, block);
+ if (! bb)
+ return EXIT_BLOCK_PTR;
+ return bb;
+ }
}
+
/* Determine all blocks' control dependences on the given edge with edge_list
EL index EDGE_INDEX, ala Morgan, Section 3.6. */
gcc_assert (INDEX_EDGE_PRED_BB (el, edge_index) != EXIT_BLOCK_PTR);
if (INDEX_EDGE_PRED_BB (el, edge_index) == ENTRY_BLOCK_PTR)
- ending_block = ENTRY_BLOCK_PTR->next_bb;
+ ending_block = single_succ (ENTRY_BLOCK_PTR);
else
ending_block = find_pdom (INDEX_EDGE_PRED_BB (el, edge_index));
}
}
-/* Find the immediate postdominator PDOM of the specified basic block BLOCK.
- This function is necessary because some blocks have negative numbers. */
-static inline basic_block
-find_pdom (basic_block block)
+/* Record all blocks' control dependences on all edges in the edge
+ list EL, ala Morgan, Section 3.6. */
+
+static void
+find_all_control_dependences (struct edge_list *el)
{
- gcc_assert (block != ENTRY_BLOCK_PTR);
+ int i;
- if (block == EXIT_BLOCK_PTR)
- return EXIT_BLOCK_PTR;
- else
- {
- basic_block bb = get_immediate_dominator (CDI_POST_DOMINATORS, block);
- if (! bb)
- return EXIT_BLOCK_PTR;
- return bb;
- }
+ for (i = 0; i < NUM_EDGES (el); ++i)
+ find_control_dependence (el, i);
}
-\f
-#define NECESSARY(stmt) stmt->common.asm_written_flag
/* If STMT is not already marked necessary, mark it, and add it to the
worklist if ADD_TO_WORKLIST is true. */
static inline void
-mark_stmt_necessary (tree stmt, bool add_to_worklist)
+mark_stmt_necessary (gimple stmt, bool add_to_worklist)
{
gcc_assert (stmt);
- gcc_assert (stmt != error_mark_node);
- gcc_assert (!DECL_P (stmt));
- if (NECESSARY (stmt))
+ if (gimple_plf (stmt, STMT_NECESSARY))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Marking useful stmt: ");
- print_generic_stmt (dump_file, stmt, TDF_SLIM);
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
- NECESSARY (stmt) = 1;
+ gimple_set_plf (stmt, STMT_NECESSARY, true);
if (add_to_worklist)
- VARRAY_PUSH_TREE (worklist, stmt);
+ VEC_safe_push (gimple, heap, worklist, stmt);
}
-/* Mark the statement defining operand OP as necessary. PHIONLY is true
- if we should only mark it necessary if it is a phi node. */
+
+/* Mark the statement defining operand OP as necessary. */
static inline void
-mark_operand_necessary (tree op, bool phionly)
+mark_operand_necessary (tree op)
{
- tree stmt;
+ gimple stmt;
int ver;
gcc_assert (op);
stmt = SSA_NAME_DEF_STMT (op);
gcc_assert (stmt);
- if (NECESSARY (stmt)
- || IS_EMPTY_STMT (stmt)
- || (phionly && TREE_CODE (stmt) != PHI_NODE))
+ if (gimple_plf (stmt, STMT_NECESSARY) || gimple_nop_p (stmt))
return;
- NECESSARY (stmt) = 1;
- VARRAY_PUSH_TREE (worklist, stmt);
+ gimple_set_plf (stmt, STMT_NECESSARY, true);
+ VEC_safe_push (gimple, heap, worklist, stmt);
}
-\f
-/* Mark STMT as necessary if it is obviously is. Add it to the worklist if
+
+/* Mark STMT as necessary if it obviously is. Add it to the worklist if
it can make other statements necessary.
If AGGRESSIVE is false, control statements are conservatively marked as
necessary. */
static void
-mark_stmt_if_obviously_necessary (tree stmt, bool aggressive)
+mark_stmt_if_obviously_necessary (gimple stmt, bool aggressive)
{
- v_may_def_optype v_may_defs;
- v_must_def_optype v_must_defs;
- stmt_ann_t ann;
- tree op, def;
- ssa_op_iter iter;
-
- /* Statements that are implicitly live. Most function calls, asm and return
- statements are required. Labels and BIND_EXPR nodes are kept because
- they are control flow, and we have no way of knowing whether they can be
- removed. DCE can eliminate all the other statements in a block, and CFG
- can then remove the block and labels. */
- switch (TREE_CODE (stmt))
+ tree lhs = NULL_TREE;
+ /* With non-call exceptions, we have to assume that all statements could
+ throw. If a statement may throw, it is inherently necessary. */
+ if (flag_non_call_exceptions
+ && stmt_could_throw_p (stmt))
{
- case BIND_EXPR:
- case LABEL_EXPR:
- case CASE_LABEL_EXPR:
+ mark_stmt_necessary (stmt, true);
+ return;
+ }
+
+ /* Statements that are implicitly live. Most function calls, asm
+ and return statements are required. Labels and GIMPLE_BIND nodes
+ are kept because they are control flow, and we have no way of
+ knowing whether they can be removed. DCE can eliminate all the
+ other statements in a block, and CFG can then remove the block
+ and labels. */
+ switch (gimple_code (stmt))
+ {
+ case GIMPLE_PREDICT:
+ case GIMPLE_LABEL:
mark_stmt_necessary (stmt, false);
return;
- case ASM_EXPR:
- case RESX_EXPR:
- case RETURN_EXPR:
+ case GIMPLE_ASM:
+ case GIMPLE_RESX:
+ case GIMPLE_RETURN:
+ case GIMPLE_CHANGE_DYNAMIC_TYPE:
mark_stmt_necessary (stmt, true);
return;
- case CALL_EXPR:
+ case GIMPLE_CALL:
/* Most, but not all function calls are required. Function calls that
produce no result and have no side effects (i.e. const pure
functions) are unnecessary. */
- if (TREE_SIDE_EFFECTS (stmt))
- mark_stmt_necessary (stmt, true);
- return;
-
- case MODIFY_EXPR:
- op = get_call_expr_in (stmt);
- if (op && TREE_SIDE_EFFECTS (op))
+ if (gimple_has_side_effects (stmt))
{
mark_stmt_necessary (stmt, true);
return;
}
-
+ if (!gimple_call_lhs (stmt))
+ return;
+ lhs = gimple_call_lhs (stmt);
+ /* Fall through */
+
+ case GIMPLE_ASSIGN:
+ if (!lhs)
+ lhs = gimple_assign_lhs (stmt);
/* These values are mildly magic bits of the EH runtime. We can't
see the entire lifetime of these values until landing pads are
generated. */
- if (TREE_CODE (TREE_OPERAND (stmt, 0)) == EXC_PTR_EXPR
- || TREE_CODE (TREE_OPERAND (stmt, 0)) == FILTER_EXPR)
+ if (TREE_CODE (lhs) == EXC_PTR_EXPR
+ || TREE_CODE (lhs) == FILTER_EXPR)
{
mark_stmt_necessary (stmt, true);
return;
}
break;
- case GOTO_EXPR:
+ case GIMPLE_GOTO:
gcc_assert (!simple_goto_p (stmt));
mark_stmt_necessary (stmt, true);
return;
- case COND_EXPR:
- gcc_assert (EDGE_COUNT (bb_for_stmt (stmt)->succs) == 2);
+ case GIMPLE_COND:
+ gcc_assert (EDGE_COUNT (gimple_bb (stmt)->succs) == 2);
/* Fall through. */
- case SWITCH_EXPR:
+ case GIMPLE_SWITCH:
if (! aggressive)
mark_stmt_necessary (stmt, true);
break;
break;
}
- ann = stmt_ann (stmt);
-
/* If the statement has volatile operands, it needs to be preserved.
Same for statements that can alter control flow in unpredictable
ways. */
- if (ann->has_volatile_ops || is_ctrl_altering_stmt (stmt))
+ if (gimple_has_volatile_ops (stmt) || is_ctrl_altering_stmt (stmt))
{
mark_stmt_necessary (stmt, true);
return;
}
- get_stmt_operands (stmt);
-
- FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
+ if (is_hidden_global_store (stmt))
{
- if (is_global_var (SSA_NAME_VAR (def)))
- {
- mark_stmt_necessary (stmt, true);
- return;
- }
+ mark_stmt_necessary (stmt, true);
+ return;
}
- /* Check virtual definitions. If we get here, the only virtual
- definitions we should see are those generated by assignment
- statements. */
- v_may_defs = V_MAY_DEF_OPS (ann);
- v_must_defs = V_MUST_DEF_OPS (ann);
- if (NUM_V_MAY_DEFS (v_may_defs) > 0 || NUM_V_MUST_DEFS (v_must_defs) > 0)
- {
- tree lhs;
-
- gcc_assert (TREE_CODE (stmt) == MODIFY_EXPR);
+ return;
+}
- /* Note that we must not check the individual virtual operands
- here. In particular, if this is an aliased store, we could
- end up with something like the following (SSA notation
- redacted for brevity):
- foo (int *p, int i)
- {
- int x;
- p_1 = (i_2 > 3) ? &x : p_1;
+/* Make corresponding control dependent edges necessary. We only
+ have to do this once for each basic block, so we clear the bitmap
+ after we're done. */
+static void
+mark_control_dependent_edges_necessary (basic_block bb, struct edge_list *el)
+{
+ bitmap_iterator bi;
+ unsigned edge_number;
- # x_4 = V_MAY_DEF <x_3>
- *p_1 = 5;
+ gcc_assert (bb != EXIT_BLOCK_PTR);
- return 2;
- }
+ if (bb == ENTRY_BLOCK_PTR)
+ return;
- Notice that the store to '*p_1' should be preserved, if we
- were to check the virtual definitions in that store, we would
- not mark it needed. This is because 'x' is not a global
- variable.
+ EXECUTE_IF_CONTROL_DEPENDENT (bi, bb->index, edge_number)
+ {
+ gimple stmt;
+ basic_block cd_bb = INDEX_EDGE_PRED_BB (el, edge_number);
- Therefore, we check the base address of the LHS. If the
- address is a pointer, we check if its name tag or type tag is
- a global variable. Otherwise, we check if the base variable
- is a global. */
- lhs = TREE_OPERAND (stmt, 0);
- if (REFERENCE_CLASS_P (lhs))
- lhs = get_base_address (lhs);
+ if (TEST_BIT (last_stmt_necessary, cd_bb->index))
+ continue;
+ SET_BIT (last_stmt_necessary, cd_bb->index);
- if (lhs == NULL_TREE)
- {
- /* If LHS is NULL, it means that we couldn't get the base
- address of the reference. In which case, we should not
- remove this store. */
- mark_stmt_necessary (stmt, true);
- }
- else if (DECL_P (lhs))
- {
- /* If the store is to a global symbol, we need to keep it. */
- if (is_global_var (lhs))
- mark_stmt_necessary (stmt, true);
- }
- else if (INDIRECT_REF_P (lhs))
- {
- tree ptr = TREE_OPERAND (lhs, 0);
- struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
- tree nmt = (pi) ? pi->name_mem_tag : NULL_TREE;
- tree tmt = var_ann (SSA_NAME_VAR (ptr))->type_mem_tag;
-
- /* If either the name tag or the type tag for PTR is a
- global variable, then the store is necessary. */
- if ((nmt && is_global_var (nmt))
- || (tmt && is_global_var (tmt)))
- {
- mark_stmt_necessary (stmt, true);
- return;
- }
- }
- else
- gcc_unreachable ();
+ stmt = last_stmt (cd_bb);
+ if (stmt && is_ctrl_stmt (stmt))
+ mark_stmt_necessary (stmt, true);
}
-
- return;
}
-\f
+
+
/* Find obviously necessary statements. These are things like most function
calls, and stores to file level variables.
find_obviously_necessary_stmts (struct edge_list *el)
{
basic_block bb;
- block_stmt_iterator i;
+ gimple_stmt_iterator gsi;
edge e;
+ gimple phi, stmt;
FOR_EACH_BB (bb)
{
- tree phi;
-
- /* Check any PHI nodes in the block. */
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ /* PHI nodes are never inherently necessary. */
+ for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
- NECESSARY (phi) = 0;
-
- /* PHIs for virtual variables do not directly affect code
- generation and need not be considered inherently necessary
- regardless of the bits set in their decl.
-
- Thus, we only need to mark PHIs for real variables which
- need their result preserved as being inherently necessary. */
- if (is_gimple_reg (PHI_RESULT (phi))
- && is_global_var (SSA_NAME_VAR (PHI_RESULT (phi))))
- mark_stmt_necessary (phi, true);
- }
+ phi = gsi_stmt (gsi);
+ gimple_set_plf (phi, STMT_NECESSARY, false);
+ }
/* Check all statements in the block. */
- for (i = bsi_start (bb); ! bsi_end_p (i); bsi_next (&i))
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
- tree stmt = bsi_stmt (i);
- NECESSARY (stmt) = 0;
+ stmt = gsi_stmt (gsi);
+ gimple_set_plf (stmt, STMT_NECESSARY, false);
mark_stmt_if_obviously_necessary (stmt, el != NULL);
}
-
- /* Mark this basic block as `not visited'. A block will be marked
- visited when the edges that it is control dependent on have been
- marked. */
- bb->flags &= ~BB_VISITED;
}
if (el)
}
}
}
-\f
-/* Make corresponding control dependent edges necessary. We only
- have to do this once for each basic block, so we clear the bitmap
- after we're done. */
-static void
-mark_control_dependent_edges_necessary (basic_block bb, struct edge_list *el)
-{
- int edge_number;
- gcc_assert (bb != EXIT_BLOCK_PTR);
- if (bb == ENTRY_BLOCK_PTR)
- return;
-
- EXECUTE_IF_CONTROL_DEPENDENT (bb->index, edge_number,
- {
- tree t;
- basic_block cd_bb = INDEX_EDGE_PRED_BB (el, edge_number);
-
- if (TEST_BIT (last_stmt_necessary, cd_bb->index))
- continue;
- SET_BIT (last_stmt_necessary, cd_bb->index);
-
- t = last_stmt (cd_bb);
- if (t && is_ctrl_stmt (t))
- mark_stmt_necessary (t, true);
- });
-}
-\f
-/* Propagate necessity using the operands of necessary statements. Process
- the uses on each statement in the worklist, and add all feeding statements
- which contribute to the calculation of this value to the worklist.
+/* Propagate necessity using the operands of necessary statements.
+ Process the uses on each statement in the worklist, and add all
+ feeding statements which contribute to the calculation of this
+ value to the worklist.
In conservative mode, EL is NULL. */
static void
propagate_necessity (struct edge_list *el)
{
- tree i;
+ gimple stmt;
bool aggressive = (el ? true : false);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\nProcessing worklist:\n");
- while (VARRAY_ACTIVE_SIZE (worklist) > 0)
+ while (VEC_length (gimple, worklist) > 0)
{
- /* Take `i' from worklist. */
- i = VARRAY_TOP_TREE (worklist);
- VARRAY_POP (worklist);
+ /* Take STMT from worklist. */
+ stmt = VEC_pop (gimple, worklist);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "processing: ");
- print_generic_stmt (dump_file, i, TDF_SLIM);
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
if (aggressive)
{
/* Mark the last statements of the basic blocks that the block
- containing `i' is control dependent on, but only if we haven't
+ containing STMT is control dependent on, but only if we haven't
already done so. */
- basic_block bb = bb_for_stmt (i);
- if (! (bb->flags & BB_VISITED))
+ basic_block bb = gimple_bb (stmt);
+ if (bb != ENTRY_BLOCK_PTR
+ && ! TEST_BIT (visited_control_parents, bb->index))
{
- bb->flags |= BB_VISITED;
+ SET_BIT (visited_control_parents, bb->index);
mark_control_dependent_edges_necessary (bb, el);
}
}
- if (TREE_CODE (i) == PHI_NODE)
+ if (gimple_code (stmt) == GIMPLE_PHI)
{
/* PHI nodes are somewhat special in that each PHI alternative has
data and control dependencies. All the statements feeding the
we also consider the control dependent edges leading to the
predecessor block associated with each PHI alternative as
necessary. */
- int k;
- for (k = 0; k < PHI_NUM_ARGS (i); k++)
+ size_t k;
+
+ for (k = 0; k < gimple_phi_num_args (stmt); k++)
{
- tree arg = PHI_ARG_DEF (i, k);
+ tree arg = PHI_ARG_DEF (stmt, k);
if (TREE_CODE (arg) == SSA_NAME)
- mark_operand_necessary (arg, false);
+ mark_operand_necessary (arg);
}
if (aggressive)
{
- for (k = 0; k < PHI_NUM_ARGS (i); k++)
+ for (k = 0; k < gimple_phi_num_args (stmt); k++)
{
- basic_block arg_bb = PHI_ARG_EDGE (i, k)->src;
- if (! (arg_bb->flags & BB_VISITED))
+ basic_block arg_bb = gimple_phi_arg_edge (stmt, k)->src;
+ if (arg_bb != ENTRY_BLOCK_PTR
+ && ! TEST_BIT (visited_control_parents, arg_bb->index))
{
- arg_bb->flags |= BB_VISITED;
+ SET_BIT (visited_control_parents, arg_bb->index);
mark_control_dependent_edges_necessary (arg_bb, el);
}
}
else
{
/* Propagate through the operands. Examine all the USE, VUSE and
- V_MAY_DEF operands in this statement. Mark all the statements
- which feed this statement's uses as necessary. */
- ssa_op_iter iter;
- tree use;
-
- get_stmt_operands (i);
-
- /* The operands of V_MAY_DEF expressions are also needed as they
+ VDEF operands in this statement. Mark all the statements
+ which feed this statement's uses as necessary. The
+ operands of VDEF expressions are also needed as they
represent potential definitions that may reach this
- statement (V_MAY_DEF operands allow us to follow def-def
+ statement (VDEF operands allow us to follow def-def
links). */
+ ssa_op_iter iter;
+ tree use;
- FOR_EACH_SSA_TREE_OPERAND (use, i, iter, SSA_OP_ALL_USES)
- mark_operand_necessary (use, false);
- }
- }
-}
-
-
-/* Propagate necessity around virtual phi nodes used in kill operands.
- The reason this isn't done during propagate_necessity is because we don't
- want to keep phis around that are just there for must-defs, unless we
- absolutely have to. After we've rewritten the reaching definitions to be
- correct in the previous part of the fixup routine, we can simply propagate
- around the information about which of these virtual phi nodes are really
- used, and set the NECESSARY flag accordingly.
- Note that we do the minimum here to ensure that we keep alive the phis that
- are actually used in the corrected SSA form. In particular, some of these
- phis may now have all of the same operand, and will be deleted by some
- other pass. */
-
-static void
-mark_really_necessary_kill_operand_phis (void)
-{
- basic_block bb;
- int i;
-
- /* Seed the worklist with the new virtual phi arguments and virtual
- uses */
- FOR_EACH_BB (bb)
- {
- block_stmt_iterator bsi;
- tree phi;
-
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
- {
- if (!is_gimple_reg (PHI_RESULT (phi)) && NECESSARY (phi))
- {
- for (i = 0; i < PHI_NUM_ARGS (phi); i++)
- mark_operand_necessary (PHI_ARG_DEF (phi, i), true);
- }
- }
-
- for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_prev (&bsi))
- {
- tree stmt = bsi_stmt (bsi);
-
- if (NECESSARY (stmt))
- {
- use_operand_p use_p;
- ssa_op_iter iter;
- FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
- SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS)
- {
- tree use = USE_FROM_PTR (use_p);
- mark_operand_necessary (use, true);
- }
- }
+ FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_ALL_USES)
+ mark_operand_necessary (use);
}
}
-
- /* Mark all virtual phis still in use as necessary, and all of their
- arguments that are phis as necessary. */
- while (VARRAY_ACTIVE_SIZE (worklist) > 0)
- {
- tree use = VARRAY_TOP_TREE (worklist);
- VARRAY_POP (worklist);
-
- for (i = 0; i < PHI_NUM_ARGS (use); i++)
- mark_operand_necessary (PHI_ARG_DEF (use, i), true);
- }
}
-\f
-
-/* Eliminate unnecessary statements. Any instruction not marked as necessary
- contributes nothing to the program, and can be deleted. */
-
-static void
-eliminate_unnecessary_stmts (void)
-{
- basic_block bb;
- block_stmt_iterator i;
-
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "\nEliminating unnecessary statements:\n");
-
- clear_special_calls ();
- FOR_EACH_BB (bb)
- {
- /* Remove dead PHI nodes. */
- remove_dead_phis (bb);
-
- /* Remove dead statements. */
- for (i = bsi_start (bb); ! bsi_end_p (i) ; )
- {
- tree t = bsi_stmt (i);
-
- stats.total++;
-
- /* If `i' is not necessary then remove it. */
- if (! NECESSARY (t))
- remove_dead_stmt (&i, bb);
- else
- {
- tree call = get_call_expr_in (t);
- if (call)
- notice_special_calls (call);
- bsi_next (&i);
- }
- }
- }
- }
-\f
/* Remove dead PHI nodes from block BB. */
-static void
+static bool
remove_dead_phis (basic_block bb)
{
- tree prev, phi;
+ bool something_changed = false;
+ gimple_seq phis;
+ gimple phi;
+ gimple_stmt_iterator gsi;
+ phis = phi_nodes (bb);
- prev = NULL_TREE;
- phi = phi_nodes (bb);
- while (phi)
+ for (gsi = gsi_start (phis); !gsi_end_p (gsi);)
{
stats.total_phis++;
+ phi = gsi_stmt (gsi);
- if (! NECESSARY (phi))
+ if (!gimple_plf (phi, STMT_NECESSARY))
{
- tree next = PHI_CHAIN (phi);
-
+ something_changed = true;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleting : ");
- print_generic_stmt (dump_file, phi, TDF_SLIM);
+ print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
- remove_phi_node (phi, prev, bb);
+ remove_phi_node (&gsi, true);
stats.removed_phis++;
- phi = next;
}
else
{
- prev = phi;
- phi = PHI_CHAIN (phi);
+ gsi_next (&gsi);
}
}
+ return something_changed;
}
-\f
-/* Remove dead statement pointed by iterator I. Receives the basic block BB
+
+
+/* Remove dead statement pointed to by iterator I. Receives the basic block BB
containing I so that we don't have to look it up. */
static void
-remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
+remove_dead_stmt (gimple_stmt_iterator *i, basic_block bb)
{
- tree t = bsi_stmt (*i);
- def_operand_p def_p;
-
- ssa_op_iter iter;
+ gimple stmt = gsi_stmt (*i);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Deleting : ");
- print_generic_stmt (dump_file, t, TDF_SLIM);
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
nothing to the program, then we not only remove it, but we also change
the flow graph so that the current block will simply fall-thru to its
immediate post-dominator. The blocks we are circumventing will be
- removed by cleaup_cfg if this change in the flow graph makes them
+ removed by cleanup_tree_cfg if this change in the flow graph makes them
unreachable. */
- if (is_ctrl_stmt (t))
+ if (is_ctrl_stmt (stmt))
{
basic_block post_dom_bb;
+
/* The post dominance info has to be up-to-date. */
- gcc_assert (dom_computed[CDI_POST_DOMINATORS] == DOM_OK);
+ gcc_assert (dom_info_state (CDI_POST_DOMINATORS) == DOM_OK);
/* Get the immediate post dominator of bb. */
post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
- /* Some blocks don't have an immediate post dominator. This can happen
- for example with infinite loops. Removing an infinite loop is an
- inappropriate transformation anyway... */
- if (! post_dom_bb)
+
+ /* There are three particularly problematical cases.
+
+ 1. Blocks that do not have an immediate post dominator. This
+ can happen with infinite loops.
+
+ 2. Blocks that are only post dominated by the exit block. These
+ can also happen for infinite loops as we create fake edges
+ in the dominator tree.
+
+ 3. If the post dominator has PHI nodes we may be able to compute
+ the right PHI args for them.
+
+ In each of these cases we must remove the control statement
+ as it may reference SSA_NAMEs which are going to be removed and
+ we remove all but one outgoing edge from the block. */
+ if (! post_dom_bb
+ || post_dom_bb == EXIT_BLOCK_PTR
+ || phi_nodes (post_dom_bb))
+ ;
+ else
{
- bsi_next (i);
- return;
+ /* Redirect the first edge out of BB to reach POST_DOM_BB. */
+ redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
+ PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
+
+ /* It is not sufficient to set cfg_altered below during edge
+ removal, in case BB has two successors and one of them
+ is POST_DOM_BB. */
+ cfg_altered = true;
}
-
- /* Redirect the first edge out of BB to reach POST_DOM_BB. */
- redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
- PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
EDGE_SUCC (bb, 0)->count = bb->count;
not have TRUE/FALSE flags. */
EDGE_SUCC (bb, 0)->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
- /* If the edge reaches any block other than the exit, then it is a
- fallthru edge; if it reaches the exit, then it is not a fallthru
- edge. */
- if (post_dom_bb != EXIT_BLOCK_PTR)
- EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU;
- else
- EDGE_SUCC (bb, 0)->flags &= ~EDGE_FALLTHRU;
+ /* The lone outgoing edge from BB will be a fallthru edge. */
+ EDGE_SUCC (bb, 0)->flags |= EDGE_FALLTHRU;
/* Remove the remaining the outgoing edges. */
- while (EDGE_COUNT (bb->succs) != 1)
- remove_edge (EDGE_SUCC (bb, 1));
+ while (!single_succ_p (bb))
+ {
+ /* FIXME. When we remove the edge, we modify the CFG, which
+ in turn modifies the dominator and post-dominator tree.
+ Is it safe to postpone recomputing the dominator and
+ post-dominator tree until the end of this pass given that
+ the post-dominators are used above? */
+ cfg_altered = true;
+ remove_edge (EDGE_SUCC (bb, 1));
+ }
}
- FOR_EACH_SSA_DEF_OPERAND (def_p, t, iter,
- SSA_OP_VIRTUAL_DEFS | SSA_OP_VIRTUAL_KILLS)
+ gsi_remove (i, true);
+ release_defs (stmt);
+}
+
+
+/* Eliminate unnecessary statements. Any instruction not marked as necessary
+ contributes nothing to the program, and can be deleted. */
+
+static bool
+eliminate_unnecessary_stmts (void)
+{
+ bool something_changed = false;
+ basic_block bb;
+ gimple_stmt_iterator gsi;
+ gimple stmt;
+ tree call;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "\nEliminating unnecessary statements:\n");
+
+ clear_special_calls ();
+ FOR_EACH_BB (bb)
{
- tree def = DEF_FROM_PTR (def_p);
- bitmap_set_bit (vars_to_rename,
- var_ann (SSA_NAME_VAR (def))->uid);
+ /* Remove dead PHI nodes. */
+ something_changed |= remove_dead_phis (bb);
}
- bsi_remove (i);
- release_defs (t);
+
+ FOR_EACH_BB (bb)
+ {
+ /* Remove dead statements. */
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
+ {
+ stmt = gsi_stmt (gsi);
+
+ stats.total++;
+
+ /* If GSI is not necessary then remove it. */
+ if (!gimple_plf (stmt, STMT_NECESSARY))
+ {
+ remove_dead_stmt (&gsi, bb);
+ something_changed = true;
+ }
+ else if (is_gimple_call (stmt))
+ {
+ call = gimple_call_fndecl (stmt);
+ if (call)
+ {
+ tree name;
+ gimple g;
+
+ /* When LHS of var = call (); is dead, simplify it into
+ call (); saving one operand. */
+ name = gimple_call_lhs (stmt);
+ if (name && TREE_CODE (name) == SSA_NAME
+ && !TEST_BIT (processed, SSA_NAME_VERSION (name)))
+ {
+ something_changed = true;
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Deleting LHS of call: ");
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
+ fprintf (dump_file, "\n");
+ }
+
+ push_stmt_changes (gsi_stmt_ptr (&gsi));
+ g = gimple_copy (stmt);
+ gimple_call_set_lhs (g, NULL_TREE);
+ gsi_replace (&gsi, g, false);
+ maybe_clean_or_replace_eh_stmt (stmt, g);
+ mark_symbols_for_renaming (g);
+ pop_stmt_changes (gsi_stmt_ptr (&gsi));
+ release_ssa_name (name);
+ }
+ notice_special_calls (stmt);
+ }
+ gsi_next (&gsi);
+ }
+ else
+ {
+ gsi_next (&gsi);
+ }
+ }
+ }
+
+ return something_changed;
}
-\f
+
+
/* Print out removed statement statistics. */
static void
print_stats (void)
{
- if (dump_file && (dump_flags & (TDF_STATS|TDF_DETAILS)))
- {
- float percg;
+ float percg;
- percg = ((float) stats.removed / (float) stats.total) * 100;
- fprintf (dump_file, "Removed %d of %d statements (%d%%)\n",
- stats.removed, stats.total, (int) percg);
+ percg = ((float) stats.removed / (float) stats.total) * 100;
+ fprintf (dump_file, "Removed %d of %d statements (%d%%)\n",
+ stats.removed, stats.total, (int) percg);
- if (stats.total_phis == 0)
- percg = 0;
- else
- percg = ((float) stats.removed_phis / (float) stats.total_phis) * 100;
+ if (stats.total_phis == 0)
+ percg = 0;
+ else
+ percg = ((float) stats.removed_phis / (float) stats.total_phis) * 100;
- fprintf (dump_file, "Removed %d of %d PHI nodes (%d%%)\n",
- stats.removed_phis, stats.total_phis, (int) percg);
- }
+ fprintf (dump_file, "Removed %d of %d PHI nodes (%d%%)\n",
+ stats.removed_phis, stats.total_phis, (int) percg);
}
-\f
+
/* Initialization for this pass. Set up the used data structures. */
static void
{
int i;
- control_dependence_map
- = xmalloc (last_basic_block * sizeof (bitmap));
+ control_dependence_map = XNEWVEC (bitmap, last_basic_block);
for (i = 0; i < last_basic_block; ++i)
- control_dependence_map[i] = BITMAP_XMALLOC ();
+ control_dependence_map[i] = BITMAP_ALLOC (NULL);
last_stmt_necessary = sbitmap_alloc (last_basic_block);
sbitmap_zero (last_stmt_necessary);
processed = sbitmap_alloc (num_ssa_names + 1);
sbitmap_zero (processed);
- VARRAY_TREE_INIT (worklist, 64, "work list");
+ worklist = VEC_alloc (gimple, heap, 64);
+ cfg_altered = false;
}
/* Cleanup after this pass. */
int i;
for (i = 0; i < last_basic_block; ++i)
- BITMAP_XFREE (control_dependence_map[i]);
+ BITMAP_FREE (control_dependence_map[i]);
free (control_dependence_map);
+ sbitmap_free (visited_control_parents);
sbitmap_free (last_stmt_necessary);
}
sbitmap_free (processed);
+
+ VEC_free (gimple, heap, worklist);
}
-\f
+
/* Main routine to eliminate dead code.
AGGRESSIVE controls the aggressiveness of the algorithm.
as the last tree SSA pass, but keep this in mind when you
start experimenting with pass ordering. */
-static void
+static unsigned int
perform_tree_ssa_dce (bool aggressive)
{
struct edge_list *el = NULL;
+ bool something_changed = 0;
tree_dce_init (aggressive);
find_all_control_dependences (el);
timevar_pop (TV_CONTROL_DEPENDENCES);
+ visited_control_parents = sbitmap_alloc (last_basic_block);
+ sbitmap_zero (visited_control_parents);
+
mark_dfs_back_edges ();
}
propagate_necessity (el);
- mark_really_necessary_kill_operand_phis ();
- eliminate_unnecessary_stmts ();
+ something_changed |= eliminate_unnecessary_stmts ();
+ something_changed |= cfg_altered;
- if (aggressive)
- free_dominance_info (CDI_POST_DOMINATORS);
+ /* We do not update postdominators, so free them unconditionally. */
+ free_dominance_info (CDI_POST_DOMINATORS);
- cleanup_tree_cfg ();
+ /* If we removed paths in the CFG, then we need to update
+ dominators as well. I haven't investigated the possibility
+ of incrementally updating dominators. */
+ if (cfg_altered)
+ free_dominance_info (CDI_DOMINATORS);
+
+ statistics_counter_event (cfun, "Statements deleted", stats.removed);
+ statistics_counter_event (cfun, "PHI nodes deleted", stats.removed_phis);
/* Debugging dumps. */
- if (dump_file)
- {
- dump_function_to_file (current_function_decl, dump_file, dump_flags);
- print_stats ();
- }
+ if (dump_file && (dump_flags & (TDF_STATS|TDF_DETAILS)))
+ print_stats ();
tree_dce_done (aggressive);
free_edge_list (el);
+
+ if (something_changed)
+ return (TODO_update_ssa | TODO_cleanup_cfg | TODO_ggc_collect
+ | TODO_remove_unused_locals);
+ else
+ return 0;
}
/* Pass entry points. */
-static void
+static unsigned int
tree_ssa_dce (void)
{
- perform_tree_ssa_dce (/*aggressive=*/false);
+ return perform_tree_ssa_dce (/*aggressive=*/false);
}
-static void
+static unsigned int
+tree_ssa_dce_loop (void)
+{
+ unsigned int todo;
+ todo = perform_tree_ssa_dce (/*aggressive=*/false);
+ if (todo)
+ {
+ free_numbers_of_iterations_estimates ();
+ scev_reset ();
+ }
+ return todo;
+}
+
+static unsigned int
tree_ssa_cd_dce (void)
{
- perform_tree_ssa_dce (/*aggressive=*/optimize >= 2);
+ return perform_tree_ssa_dce (/*aggressive=*/optimize >= 2);
}
static bool
return flag_tree_dce != 0;
}
-struct tree_opt_pass pass_dce =
+struct gimple_opt_pass pass_dce =
{
+ {
+ GIMPLE_PASS,
"dce", /* name */
gate_dce, /* gate */
tree_ssa_dce, /* execute */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_DCE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_fix_def_def_chains |TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
- 0 /* letter */
+ TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ }
};
-struct tree_opt_pass pass_cd_dce =
+struct gimple_opt_pass pass_dce_loop =
{
+ {
+ GIMPLE_PASS,
+ "dceloop", /* name */
+ gate_dce, /* gate */
+ tree_ssa_dce_loop, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_TREE_DCE, /* tv_id */
+ PROP_cfg | PROP_ssa, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ }
+};
+
+struct gimple_opt_pass pass_cd_dce =
+{
+ {
+ GIMPLE_PASS,
"cddce", /* name */
gate_dce, /* gate */
tree_ssa_cd_dce, /* execute */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_CD_DCE, /* tv_id */
- PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ PROP_cfg | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_fix_def_def_chains | TODO_ggc_collect | TODO_verify_ssa | TODO_verify_flow,
- /* todo_flags_finish */
- 0 /* letter */
+ TODO_dump_func | TODO_verify_ssa
+ | TODO_verify_flow /* todo_flags_finish */
+ }
};
-
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