Commit f70b9563 authored by Michael Beck's avatar Michael Beck
Browse files

calculate the number of uses of every address, this allows an early exit

when searching for RAR and WAW

[r4269]
parent 32f76b63
......@@ -134,6 +134,9 @@ static int update_exc(ldst_info_t *info, ir_node *block, int pos)
return 0;
}
#define get_irn_out_n(node) (unsigned)get_irn_link(node)
#define set_irn_out_n(node, n) set_irn_link(adr, (void *)(n))
/**
* walker, collects all Load/Store/Proj nodes
*
......@@ -146,12 +149,27 @@ static void collect_nodes(ir_node *node, void *env)
walk_env_t *wenv = env;
if (get_irn_op(node) == op_Proj) {
ir_node *adr;
ir_op *op;
pred = get_Proj_pred(node);
op = get_irn_op(pred);
if (get_irn_op(pred) == op_Load || get_irn_op(pred) == op_Store) {
if (op == op_Load) {
adr = get_Load_ptr(pred);
ldst_info = get_ldst_info(pred, wenv);
wenv->changes |= update_projs(ldst_info, node);
set_irn_out_n(adr, get_irn_out_n(adr) + 1);
}
else if (op == op_Store) {
adr = get_Store_ptr(pred);
ldst_info = get_ldst_info(pred, wenv);
wenv->changes |= update_projs(ldst_info, node);
set_irn_out_n(adr, get_irn_out_n(adr) + 1);
}
}
else if (get_irn_op(node) == op_Block) { /* check, if it's an exception block */
......@@ -194,6 +212,47 @@ static int optimize_load(ir_node *load)
ir_node *pred, *mem, *ptr;
int res = 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.
*
* This optimizes some often used OO constructs,
* like x = new O; x->t;
*/
if (info->projs[pn_Load_X_except]) {
if (get_irn_op(ptr) == op_Sel) {
ir_node *mem = get_Sel_mem(ptr);
if (get_irn_op(mem) == op_Alloc) {
/* ok, check the types */
entity *ent = get_Sel_entity(ptr);
type *s_type = get_entity_type(ent);
type *a_type = get_Alloc_type(mem);
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 */
exchange(info->projs[pn_Load_X_except], new_Bad());
info->projs[pn_Load_X_except] = NULL;
}
}
}
else if (get_irn_op(ptr) == op_Alloc) {
/* simple case: a direct load after an Alloc. Firm Alloc throw
* an exception in case of out-of-memory. So, there is no way for an
* exception in this load.
* This code is constructed by the "exception lowering" in the Jack compiler.
*/
exchange(info->projs[pn_Load_X_except], new_Bad());
info->projs[pn_Load_X_except] = NULL;
}
}
/* do NOT touch volatile loads for now */
if (get_Load_volatility(load) == volatility_is_volatile)
return 0;
......@@ -206,10 +265,7 @@ static int optimize_load(ir_node *load)
return 1;
}
/* the address of the load to be optimized */
ptr = get_Load_ptr(load);
/* the mem of the load. Must still be returned after optimization */
/* the mem of the Load. Must still be returned after optimization */
mem = get_Load_mem(load);
if ((get_irn_opcode(ptr) == iro_SymConst) && (get_SymConst_kind(ptr) == symconst_addr_ent)) {
......@@ -253,6 +309,11 @@ static int optimize_load(ir_node *load)
}
}
/* 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;
/* follow the memory chain as long as there are only Loads */
for (pred = skip_Proj(mem); ; pred = skip_Proj(get_Load_mem(pred))) {
......@@ -268,15 +329,15 @@ static int optimize_load(ir_node *load)
ldst_info_t *pred_info = get_irn_link(pred);
/*
* a load immediately after a store -- a read after write.
* We may remove the Load, if both load & Store does not have an exception handler
* a Load immediately after a Store -- a read after write.
* We may remove the Load, if both Load & Store does not have an exception handler
* 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 :-(
* We could make it a little bit better if we would know that the exception
* handler of teh Store jumps directly to the end...
* handler of the Store jumps directly to the end...
*/
if ((!pred_info->projs[pn_Store_X_except] && !info->projs[pn_Load_X_except]) ||
get_nodes_block(load) == get_nodes_block(pred)) {
......@@ -295,12 +356,12 @@ static int optimize_load(ir_node *load)
else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
get_Load_mode(pred) == load_mode) {
/*
* a load after a load -- a read after read.
* a Load after a Load -- a read after read.
* We may remove the second Load, if it does not have an exception handler
* 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
* Here, there is no need to check if the previos 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)) {
......@@ -334,7 +395,7 @@ static int optimize_load(ir_node *load)
}
}
/* follow only load chains */
/* follow only Load chains */
if (get_irn_op(pred) != op_Load)
break;
}
......@@ -361,11 +422,16 @@ static int optimize_store(ir_node *store)
* is possible *(type1 *)p = a; *(type2 *)p = b ...
*/
block = get_nodes_block(store);
ptr = get_Store_ptr(store);
/* 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;
block = get_nodes_block(store);
mem = get_Store_mem(store);
value = get_Store_value(store);
mode = get_irn_mode(value);
/* follow the memory chain as long as there are only Loads */
......@@ -375,7 +441,7 @@ static int optimize_store(ir_node *store)
if (get_irn_op(pred) == op_Store && get_Store_ptr(pred) == ptr &&
get_nodes_block(pred) == block && get_irn_mode(get_Store_value(pred)) == mode) {
/*
* a store after a store in the same block -- a write after write.
* a Store after a Store in the same block -- a write after write.
* We may remove the first Store, if it does not have an exception handler.
*
* TODO: What, if both have the same exception handler ???
......@@ -389,7 +455,7 @@ static int optimize_store(ir_node *store)
else if (get_irn_op(pred) == op_Load && get_Load_ptr(pred) == ptr &&
value == pred_info->projs[pn_Load_res]) {
/*
* a store of a value after a load -- a write after read.
* a Store of a value after a Load -- a write after read.
* We may remove the second Store, if it does not have an exception handler.
*/
if (! info->projs[pn_Store_X_except]) {
......@@ -399,7 +465,7 @@ static int optimize_store(ir_node *store)
}
}
/* follow only load chains */
/* follow only Load chains */
if (get_irn_op(pred) != op_Load)
break;
}
......
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