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-rw-r--r--gcc/tree-ssa-dce.c135
1 files changed, 108 insertions, 27 deletions
diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 341b768..2c68861 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -112,7 +112,7 @@ 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);
+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 *);
@@ -234,10 +234,11 @@ mark_stmt_necessary (tree stmt, bool add_to_worklist)
VARRAY_PUSH_TREE (worklist, stmt);
}
-/* Mark the statement defining operand OP as necessary. */
+/* Mark the statement defining operand OP as necessary. PHIONLY is true
+ if we should only mark it necessary if it is a phi node. */
static inline void
-mark_operand_necessary (tree op)
+mark_operand_necessary (tree op, bool phionly)
{
tree stmt;
int ver;
@@ -253,7 +254,8 @@ mark_operand_necessary (tree op)
gcc_assert (stmt);
if (NECESSARY (stmt)
- || IS_EMPTY_STMT (stmt))
+ || IS_EMPTY_STMT (stmt)
+ || (phionly && TREE_CODE (stmt) != PHI_NODE))
return;
NECESSARY (stmt) = 1;
@@ -592,7 +594,7 @@ propagate_necessity (struct edge_list *el)
{
tree arg = PHI_ARG_DEF (i, k);
if (TREE_CODE (arg) == SSA_NAME)
- mark_operand_necessary (arg);
+ mark_operand_necessary (arg, false);
}
if (aggressive)
@@ -624,11 +626,79 @@ propagate_necessity (struct edge_list *el)
links). */
FOR_EACH_SSA_TREE_OPERAND (use, i, iter, SSA_OP_ALL_USES)
- mark_operand_necessary (use);
+ 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);
+ }
+ }
+ }
+ }
+
+ /* 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);
+ }
+}
+
+
+
/* Eliminate unnecessary statements. Any instruction not marked as necessary
contributes nothing to the program, and can be deleted. */
@@ -640,7 +710,7 @@ eliminate_unnecessary_stmts (void)
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\nEliminating unnecessary statements:\n");
-
+
clear_special_calls ();
FOR_EACH_BB (bb)
{
@@ -650,23 +720,23 @@ eliminate_unnecessary_stmts (void)
/* 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);
- }
+ 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);
+ }
}
}
-}
+ }
/* Remove dead PHI nodes from block BB. */
@@ -711,6 +781,9 @@ static void
remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
{
tree t = bsi_stmt (*i);
+ def_operand_p def_p;
+
+ ssa_op_iter iter;
if (dump_file && (dump_flags & TDF_DETAILS))
{
@@ -765,9 +838,16 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
while (EDGE_COUNT (bb->succs) != 1)
remove_edge (EDGE_SUCC (bb, 1));
}
-
- bsi_remove (i);
- release_defs (t);
+
+ FOR_EACH_SSA_DEF_OPERAND (def_p, t, iter,
+ SSA_OP_VIRTUAL_DEFS | SSA_OP_VIRTUAL_KILLS)
+ {
+ tree def = DEF_FROM_PTR (def_p);
+ bitmap_set_bit (vars_to_rename,
+ var_ann (SSA_NAME_VAR (def))->uid);
+ }
+ bsi_remove (i);
+ release_defs (t);
}
/* Print out removed statement statistics. */
@@ -875,6 +955,7 @@ perform_tree_ssa_dce (bool aggressive)
propagate_necessity (el);
+ mark_really_necessary_kill_operand_phis ();
eliminate_unnecessary_stmts ();
if (aggressive)
@@ -926,7 +1007,7 @@ struct tree_opt_pass pass_dce =
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
+ TODO_fix_def_def_chains |TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
0 /* letter */
};
@@ -943,7 +1024,7 @@ struct tree_opt_pass pass_cd_dce =
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_ggc_collect | TODO_verify_ssa | TODO_verify_flow,
+ TODO_fix_def_def_chains | TODO_ggc_collect | TODO_verify_ssa | TODO_verify_flow,
/* todo_flags_finish */
0 /* letter */
};