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Commit a227f303 authored by Michael Beck's avatar Michael Beck
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added more doxygen comments 

fixed optimize_load():
 - check for voltile loads first
 - fix memory leak when a graph path was constructed
 - fix return value
 - add some more checks for security

[r6254]
parent 677e7234
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Inline Side-by-side
ir/opt/ldstopt.c
View file @ a227f303
......@@ -255,12 +255,12 @@ static entity *find_constant_entity(ir_node *ptr)
/* Do not fiddle about polymorphy. */
if (is_Class_type(get_entity_owner(ent)) &&
((get_entity_n_overwrites(ent) != 0) ||
(get_entity_n_overwrittenby(ent) != 0) ) )
return NULL;
((get_entity_n_overwrites(ent) != 0) ||
(get_entity_n_overwrittenby(ent) != 0) ) )
return NULL;
if (variability_constant == get_entity_variability(ent))
return ent;
return ent;
if (is_Array_type(tp)) {
/* check bounds */
......@@ -301,29 +301,48 @@ static entity *find_constant_entity(ir_node *ptr)
}
}
/**
* Return the Selection index of a Sel node from dimension n
*/
static long get_Sel_array_index_long(ir_node *n, int dim) {
ir_node *index = get_Sel_index(n, dim);
assert(get_irn_op(index) == op_Const);
return get_tarval_long(get_Const_tarval(index));
}
/**
* Returns the accessed component graph path for an
* node computing an address.
*
* @param ptr the node computing the address
* @param depth current depth in steps upward from the root
* of the address
*/
static compound_graph_path *rec_get_accessed_path(ir_node *ptr, int depth) {
compound_graph_path *res = NULL;
entity *root, *field;
int path_len, pos;
if (get_irn_op(ptr) == op_SymConst) {
/* a SymConst. If the depth is 0, this is an access to a global
* entity and we don't need a component path, else we know
* at least it's length.
*/
assert(get_SymConst_kind(ptr) == symconst_addr_ent);
root = get_SymConst_entity(ptr);
res = (depth == 0) ? NULL : new_compound_graph_path(get_entity_type(root), depth);
}
else {
assert(get_irn_op(ptr) == op_Sel);
/* it's a Sel, go up until we find the root */
res = rec_get_accessed_path(get_Sel_ptr(ptr), depth+1);
field = get_Sel_entity(ptr);
/* fill up the step in the path at the current position */
field = get_Sel_entity(ptr);
path_len = get_compound_graph_path_length(res);
pos = path_len - depth - 1;
pos = path_len - depth - 1;
set_compound_graph_path_node(res, pos, field);
if (is_Array_type(get_entity_owner(field))) {
assert(get_Sel_n_indexs(ptr) == 1 && "multi dim arrays not implemented");
set_compound_graph_path_array_index(res, pos, get_Sel_array_index_long(ptr, 0));
......@@ -332,9 +351,9 @@ static compound_graph_path *rec_get_accessed_path(ir_node *ptr, int depth) {
return res;
}
/** Returns an access path or NULL. The access path is only
* valid, if the graph is in phase_high and _no_ address computation is used. */
* valid, if the graph is in phase_high and _no_ address computation is used.
*/
static compound_graph_path *get_accessed_path(ir_node *ptr) {
return rec_get_accessed_path(ptr, 0);
}
......@@ -350,13 +369,17 @@ static int optimize_load(ir_node *load)
entity *ent;
int res = 0;
/* do NOT touch volatile loads for now */
if (get_Load_volatility(load) == volatility_is_volatile)
return 0;
/* the address of the load to be optimized */
ptr = get_Load_ptr(load);
/*
* Check if we can remove the exception form a Load:
* this can be done, if the address is from an Sel(Alloc) and
* the Sel type is a subtype of the alloc type.
* Check if we can remove the exception from a Load:
* This can be done, if the address is from an Sel(Alloc) and
* the Sel type is a subtype of the allocated type.
*
* This optimizes some often used OO constructs,
* like x = new O; x->t;
......@@ -373,10 +396,11 @@ static int optimize_load(ir_node *load)
if (is_subclass_of(s_type, a_type)) {
/* ok, condition met: there can't be an exception because
* alloc guarantees that enough memory was allocated */
* Alloc guarantees that enough memory was allocated */
exchange(info->projs[pn_Load_X_except], new_Bad());
info->projs[pn_Load_X_except] = NULL;
res = 1;
}
}
}
......@@ -389,24 +413,20 @@ static int optimize_load(ir_node *load)
*/
exchange(info->projs[pn_Load_X_except], new_Bad());
info->projs[pn_Load_X_except] = NULL;
res = 1;
}
}
/* do NOT touch volatile loads for now */
if (get_Load_volatility(load) == volatility_is_volatile)
return 0;
/* the mem of the Load. Must still be returned after optimization */
mem = get_Load_mem(load);
if (! info->projs[pn_Load_res] && ! info->projs[pn_Load_X_except]) {
/* a Load which value is neither used nor exception checked, remove it */
mem = get_Load_mem(load);
exchange(info->projs[pn_Load_M], mem);
return 1;
}
/* the mem of the Load. Must still be returned after optimization */
mem = get_Load_mem(load);
/* Load from a constant polymorphic field, where we can resolve
polymorphy. */
new_node = transform_node_Load(load);
......@@ -436,6 +456,7 @@ static int optimize_load(ir_node *load)
if (info->projs[pn_Load_X_except]) {
exchange(info->projs[pn_Load_X_except], new_Bad());
info->projs[pn_Load_X_except] = NULL;
res = 1;
}
if (variability_constant == get_entity_variability(ent)
......@@ -449,8 +470,10 @@ static int optimize_load(ir_node *load)
*/
/* no memory */
if (info->projs[pn_Load_M])
if (info->projs[pn_Load_M]) {
exchange(info->projs[pn_Load_M], mem);
res = 1;
}
/* no result :-) */
if (info->projs[pn_Load_res]) {
......@@ -459,32 +482,17 @@ static int optimize_load(ir_node *load)
DBG_OPT_RC(load, c);
exchange(info->projs[pn_Load_res], c);
return 1;
}
}
}
else if (variability_constant == get_entity_variability(ent)) {
compound_graph_path *path;
/*
printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
get_entity_name(get_irg_entity(current_ir_graph)));
printf(" load: "); DDMN(load);
printf(" ptr: "); DDMN(ptr);
*/
path = get_accessed_path(ptr);
compound_graph_path *path = get_accessed_path(ptr);
if (path) {
ir_node *c;
assert(is_proper_compound_graph_path(path, get_compound_graph_path_length(path)-1));
c = get_compound_ent_value_by_path(ent, path);
/* printf(" cons: "); DDMN(c); */
if (info->projs[pn_Load_M])
exchange(info->projs[pn_Load_M], mem);
if (info->projs[pn_Load_res])
exchange(info->projs[pn_Load_res], copy_const_value(c));
/*
{
int j;
......@@ -496,39 +504,49 @@ static int optimize_load(ir_node *load)
}
printf("\n");
}
*/
} else {
/* We can not determine a correct access path. E.g., in jack, we load
a byte from an object to generate an exception. Happens in test program
Reflectiontest.
printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
get_entity_name(get_irg_entity(current_ir_graph)));
printf(" load: "); DDMN(load);
printf(" ptr: "); DDMN(ptr);
if (get_irn_op(ptr) == op_SymConst &&
get_SymConst_kind(ptr) == symconst_addr_ent) { printf(" "); DDMEO(get_SymConst_entity(ptr)); }
printf("cannot optimize.\n");
*/
}
}
*/
c = get_compound_ent_value_by_path(ent, path);
free_compound_graph_path(path);
/* we changed the irg, but try further */
res = 1;
/* printf(" cons: "); DDMN(c); */
if (info->projs[pn_Load_M]) {
exchange(info->projs[pn_Load_M], mem);
res = 1;
}
if (info->projs[pn_Load_res]) {
exchange(info->projs[pn_Load_res], copy_const_value(c));
return 1;
}
}
else {
/* We can not determine a correct access path. E.g., in jack, we load
a byte from an object to generate an exception. Happens in test program
Reflectiontest.
printf(">>>>>>>>>>>>> Found access to constant entity %s in function %s\n", get_entity_name(ent),
get_entity_name(get_irg_entity(current_ir_graph)));
printf(" load: "); DDMN(load);
printf(" ptr: "); DDMN(ptr);
*/
}
}
}
}
/* Check, if the address of this load is used more than once.
* If not, this load cannot be removed in any case. */
if (get_irn_out_n(ptr) <= 1)
return 0;
return res;
/* follow the memory chain as long as there are only Loads */
/* follow the memory chain as long as there are only Loads
* and try to replace current Load or Store by a previous one
*/
for (pred = skip_Proj(mem); ; pred = skip_Proj(get_Load_mem(pred))) {
/*
* BEWARE: one might think that checking the modes is useless, because
* if the pointers are identical, they refer to the same object.
* This is only true in strong typed languages, not is C were the following
* This is only true in strong typed languages, not in C were the following
* is possible a = *(type1 *)p; b = *(type2 *)p ...
*/
......@@ -542,8 +560,9 @@ static int optimize_load(ir_node *load)
* OR they are in the same block. In the latter case the Load cannot
* throw an exception when the previous Store was quiet.
*
* Why we need to check for Store Exc? If the Store cannot be executed (ROM)
* the exception handler might simply jump into the load block :-(
* Why we need to check for Store Exception? If the Store cannot
* be executed (ROM) the exception handler might simply jump into
* the load block :-(
* We could make it a little bit better if we would know that the exception
* handler of the Store jumps directly to the end...
*/
......@@ -552,14 +571,16 @@ static int optimize_load(ir_node *load)
ir_node *value = get_Store_value(pred);
DBG_OPT_RAW(load, value);
exchange(info->projs[pn_Load_res], value);
if (info->projs[pn_Load_M])
exchange(info->projs[pn_Load_M], mem);
/* no exception */
if (info->projs[pn_Load_X_except])
exchange( info->projs[pn_Load_X_except], new_Bad());
if (info->projs[pn_Load_res])
exchange(info->projs[pn_Load_res], value);
return 1;
}
}
......@@ -571,8 +592,8 @@ static int optimize_load(ir_node *load)
* OR they are in the same block. In the later case the Load cannot
* throw an exception when the previous Load was quiet.
*
* Here, there is no need to check if the previos Load has an exception hander because
* they would have exact the same exception...
* Here, there is no need to check if the previous Load has an exception
* hander because they would have exact the same exception...
*/
if (! info->projs[pn_Load_X_except] || get_nodes_block(load) == get_nodes_block(pred)) {
ldst_info_t *pred_info = get_irn_link(pred);
......@@ -581,7 +602,9 @@ static int optimize_load(ir_node *load)
if (pred_info->projs[pn_Load_res]) {
/* we need a data proj from the previous load for this optimization */
exchange( info->projs[pn_Load_res], pred_info->projs[pn_Load_res] );
if (info->projs[pn_Load_res])
exchange(info->projs[pn_Load_res], pred_info->projs[pn_Load_res]);
if (info->projs[pn_Load_M])
exchange(info->projs[pn_Load_M], mem);
}
......@@ -589,6 +612,7 @@ static int optimize_load(ir_node *load)
if (info->projs[pn_Load_res]) {
set_Proj_pred(info->projs[pn_Load_res], pred);
set_nodes_block(info->projs[pn_Load_res], get_nodes_block(pred));
pred_info->projs[pn_Load_res] = info->projs[pn_Load_res];
}
if (info->projs[pn_Load_M]) {
/* Actually, this if should not be necessary. Construct the Loads
......
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