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toplev.h (flag_delete_null_pointer_checks): Move from here to...

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* toplev.h (flag_delete_null_pointer_checks): Move from here to...
        * flags.h (flag_delete_null_pointer_checks): Here.
        * tree-flow.h (cprop_into_successor_phis): Add argument to prototype.
        * tree-phinodes.c (resize_phi_node): Initialize PHI_ARG_NONZERO.
        (add_phi_arg, remove_phi_arg_num): Similarly.
        * tree-ssa-copy.c (cprop_into_successor_phis): Propagate nonzero
        property into PHI nodes.
        * tree-ssa-dom.c: Remove redundant inclusion of flags.h.
        (record_equivalences_from_phis): If all PHI arguments are known to be
        nonzero, then the result must be nonzero as well.
        (cprop_into_phis): Pass nonzero_vars bitmap to cprop_into_successor_phis        (record_equivalences_from_stmt): Check flag_delete_null_pointer_checks
        appropriately.  Walk the USE-DEF chains and propagate nonzero property
        as appropriate.
        * tree.h (PHI_ARG_NONZERO): Define.
        (phi_arg_d): Add nonzero flag.

From-SVN: r81968
This commit is contained in:
Jeff Law 2004-05-17 20:53:55 -06:00 committed by Jeff Law
parent b4117c3061
commit dd7473111a
7 changed files with 77 additions and 21 deletions
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18
gcc/ChangeLog
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@ -1,3 +1,21 @@
2004-05-17 Jeff Law <law@redhat.com>
* toplev.h (flag_delete_null_pointer_checks): Move from here to...
* flags.h (flag_delete_null_pointer_checks): Here.
* tree-flow.h (cprop_into_successor_phis): Add argument to prototype.
* tree-phinodes.c (resize_phi_node): Initialize PHI_ARG_NONZERO.
(add_phi_arg, remove_phi_arg_num): Similarly.
* tree-ssa-copy.c (cprop_into_successor_phis): Propagate nonzero
property into PHI nodes.
* tree-ssa-dom.c: Remove redundant inclusion of flags.h.
(record_equivalences_from_phis): If all PHI arguments are known to be
nonzero, then the result must be nonzero as well.
(cprop_into_phis): Pass nonzero_vars bitmap to cprop_into_successor_phis (record_equivalences_from_stmt): Check flag_delete_null_pointer_checks
appropriately. Walk the USE-DEF chains and propagate nonzero property
as appropriate.
* tree.h (PHI_ARG_NONZERO): Define.
(phi_arg_d): Add nonzero flag.
2004-05-17 Zack Weinberg <zack@codesourcery.com>
* f: Entire directory removed

4
gcc/flags.h
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@ -323,6 +323,10 @@ extern int flag_cse_skip_blocks;
perform miscellaneous relatively-expensive optimizations. */
extern int flag_expensive_optimizations;
/* Nonzero means to use global dataflow analysis to eliminate
useless null pointer tests. */
extern int flag_delete_null_pointer_checks;
/* Nonzero means don't put addresses of constant functions in registers.
Used for compiling the Unix kernel, where strange substitutions are
done on the assembly output. */

1
gcc/toplev.h
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@ -113,7 +113,6 @@ extern int flag_loop_optimize;
extern int flag_crossjumping;
extern int flag_if_conversion;
extern int flag_if_conversion2;
extern int flag_delete_null_pointer_checks;
extern int flag_keep_static_consts;
extern int flag_peel_loops;
extern int flag_rerun_cse_after_loop;

2
gcc/tree-flow.h
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@ -575,7 +575,7 @@ extern void debug_dominator_optimization_stats (void);
extern void propagate_value (tree *, tree);
extern void replace_exp (tree *, tree);
extern bool cprop_into_stmt (tree, varray_type);
extern void cprop_into_successor_phis (basic_block, varray_type);
extern void cprop_into_successor_phis (basic_block, varray_type, bitmap);
/* In tree-flow-inline.h */
static inline int phi_arg_from_edge (tree, edge);

4
gcc/tree-phinodes.c
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@ -280,6 +280,7 @@ resize_phi_node (tree *phi, int len)
{
PHI_ARG_DEF (new_phi, i) = NULL_TREE;
PHI_ARG_EDGE (new_phi, i) = NULL;
PHI_ARG_NONZERO (new_phi, i) = false;
}
*phi = new_phi;
@ -366,6 +367,7 @@ add_phi_arg (tree *phi, tree def, edge e)
PHI_ARG_DEF (*phi, i) = def;
PHI_ARG_EDGE (*phi, i) = e;
PHI_ARG_NONZERO (*phi, i) = false;
PHI_NUM_ARGS (*phi)++;
}
@ -408,11 +410,13 @@ remove_phi_arg_num (tree phi, int i)
{
PHI_ARG_DEF (phi, i) = PHI_ARG_DEF (phi, num_elem - 1);
PHI_ARG_EDGE (phi, i) = PHI_ARG_EDGE (phi, num_elem - 1);
PHI_ARG_NONZERO (phi, i) = PHI_ARG_NONZERO (phi, num_elem - 1);
}
/* Shrink the vector and return. */
PHI_ARG_DEF (phi, num_elem - 1) = NULL_TREE;
PHI_ARG_EDGE (phi, num_elem - 1) = NULL;
PHI_ARG_NONZERO (phi, num_elem - 1) = false;
PHI_NUM_ARGS (phi)--;
/* If we removed the last PHI argument, then go ahead and

67
gcc/tree-ssa-dom.c
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@ -40,7 +40,6 @@ Boston, MA 02111-1307, USA. */
#include "domwalk.h"
#include "real.h"
#include "tree-pass.h"
#include "flags.h"
#include "langhooks.h"
/* This file implements optimizations on the dominator tree. */
@ -1314,7 +1313,12 @@ dom_opt_finalize_block (struct dom_walk_data *walk_data, basic_block bb)
Ignoring any alternatives which are the same as the result, if
all the alternatives are equal, then the PHI node creates an
equivalence. */
equivalence.
Additionally, if all the PHI alternatives are known to have a nonzero
value, then the result of this PHI is known to have a nonzero value,
even if we do not know its exact value. */
static void
record_equivalences_from_phis (struct dom_walk_data *walk_data, basic_block bb)
{
@ -1367,6 +1371,17 @@ record_equivalences_from_phis (struct dom_walk_data *walk_data, basic_block bb)
&& may_propagate_copy (lhs, rhs))
set_value_for (lhs, rhs, const_and_copies);
/* Now see if we know anything about the nonzero property for the
result of this PHI. */
for (i = 0; i < PHI_NUM_ARGS (phi); i++)
{
if (!PHI_ARG_NONZERO (phi, i))
break;
}
if (i == PHI_NUM_ARGS (phi))
bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
register_new_def (lhs, &bd->block_defs);
}
}
@ -2257,7 +2272,7 @@ static void
cprop_into_phis (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
basic_block bb)
{
cprop_into_successor_phis (bb, const_and_copies);
cprop_into_successor_phis (bb, const_and_copies, nonzero_vars);
}
/* Search for redundant computations in STMT. If any are found, then
@ -2422,25 +2437,39 @@ record_equivalences_from_stmt (tree stmt,
/* Look at both sides for pointer dereferences. If we find one, then
the pointer must be nonnull and we can enter that equivalence into
the hash tables. */
for (i = 0; i < 2; i++)
{
tree t = TREE_OPERAND (stmt, i);
if (flag_delete_null_pointer_checks)
for (i = 0; i < 2; i++)
{
tree t = TREE_OPERAND (stmt, i);
/* Strip away any COMPONENT_REFs. */
while (TREE_CODE (t) == COMPONENT_REF)
t = TREE_OPERAND (t, 0);
/* Strip away any COMPONENT_REFs. */
while (TREE_CODE (t) == COMPONENT_REF)
t = TREE_OPERAND (t, 0);
/* Now see if this is a pointer dereference. */
if (TREE_CODE (t) == INDIRECT_REF)
{
tree op = TREE_OPERAND (t, 0);
/* Now see if this is a pointer dereference. */
if (TREE_CODE (t) == INDIRECT_REF)
{
tree op = TREE_OPERAND (t, 0);
/* If the pointer is a SSA variable, then enter new
equivalences into the hash table. */
if (TREE_CODE (op) == SSA_NAME)
record_var_is_nonzero (op, block_nonzero_vars_p);
}
}
/* If the pointer is a SSA variable, then enter new
equivalences into the hash table. */
while (TREE_CODE (op) == SSA_NAME)
{
tree def = SSA_NAME_DEF_STMT (op);
record_var_is_nonzero (op, block_nonzero_vars_p);
/* And walk up the USE-DEF chains noting other SSA_NAMEs
which are known to have a nonzero value. */
if (def
&& TREE_CODE (def) == MODIFY_EXPR
&& TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
else
break;
}
}
}
/* A memory store, even an aliased store, creates a useful
equivalence. By exchanging the LHS and RHS, creating suitable

2
gcc/tree.h
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@ -1203,6 +1203,7 @@ struct tree_ssa_name GTY(())
#define PHI_ARG_ELT(NODE, I) PHI_NODE_ELT_CHECK (NODE, I)
#define PHI_ARG_EDGE(NODE, I) PHI_NODE_ELT_CHECK (NODE, I).e
#define PHI_ARG_DEF(NODE, I) PHI_NODE_ELT_CHECK (NODE, I).def
#define PHI_ARG_NONZERO(NODE, I) PHI_NODE_ELT_CHECK (NODE, I).nonzero
struct edge_def;
@ -1210,6 +1211,7 @@ struct phi_arg_d GTY(())
{
tree def;
struct edge_def * GTY((skip (""))) e;
bool nonzero;
};
struct tree_phi_node GTY(())