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Reuse unused 'context' variables to minimize stack usage (-llvm-api)

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gingerBill
2021-04-22 16:56:02 +01:00
parent 01db195b47
commit 896057b5a7
2 changed files with 40 additions and 5 deletions
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src/llvm_backend.cpp
+39 -5
View File
@@ -391,11 +391,37 @@ void lb_addr_store(lbProcedure *p, lbAddr addr, lbValue value) {
lb_insert_dynamic_map_key_and_value(p, addr, addr.map.type, addr.map.key, value, p->curr_stmt);
return;
} else if (addr.kind == lbAddr_Context) {
lbValue old = lb_addr_load(p, lb_find_or_generate_context_ptr(p));
lbAddr next_addr = lb_add_local_generated(p, t_context, true);
lb_addr_store(p, next_addr, old);
lb_push_context_onto_stack(p, next_addr);
lbValue next = lb_addr_get_ptr(p, next_addr);
lbAddr old_addr = lb_find_or_generate_context_ptr(p);
// IMPORTANT NOTE(bill, 2021-04-22): reuse unused 'context' variables to minimize stack usage
// This has to be done manually since the optimizer cannot determine when this is possible
bool create_new = true;
for_array(i, p->context_stack) {
lbContextData *ctx_data = &p->context_stack[i];
if (ctx_data->ctx.addr.value == old_addr.addr.value) {
if (ctx_data->uses > 0) {
create_new = true;
} else if (p->scope_index > ctx_data->scope_index) {
create_new = true;
} else {
// gb_printf_err("%.*s (curr:%td) (ctx:%td) (uses:%td)\n", LIT(p->name), p->scope_index, ctx_data->scope_index, ctx_data->uses);
create_new = false;
}
break;
}
}
lbValue next = {};
if (create_new) {
lbValue old = lb_addr_load(p, old_addr);
lbAddr next_addr = lb_add_local_generated(p, t_context, true);
lb_addr_store(p, next_addr, old);
lb_push_context_onto_stack(p, next_addr);
next = next_addr.addr;
} else {
next = old_addr.addr;
}
if (addr.ctx.sel.index.count > 0) {
lbValue lhs = lb_emit_deep_field_gep(p, next, addr.ctx.sel);
@@ -623,6 +649,13 @@ lbValue lb_addr_load(lbProcedure *p, lbAddr const &addr) {
}
} else if (addr.kind == lbAddr_Context) {
lbValue a = addr.addr;
for_array(i, p->context_stack) {
lbContextData *ctx_data = &p->context_stack[i];
if (ctx_data->ctx.addr.value == a.value) {
ctx_data->uses += 1;
break;
}
}
a.value = LLVMBuildPointerCast(p->builder, a.value, lb_type(p->module, t_context_ptr), "");
if (addr.ctx.sel.index.count > 0) {
@@ -7570,6 +7603,7 @@ lbContextData *lb_push_context_onto_stack_from_implicit_parameter(lbProcedure *p
lbContextData *cd = array_add_and_get(&p->context_stack);
cd->ctx = ctx_addr;
cd->scope_index = -1;
cd->uses = +1; // make sure it has been used already
return cd;
}
src/llvm_backend.hpp
+1
View File
@@ -157,6 +157,7 @@ struct lbBranchBlocks {
struct lbContextData {
lbAddr ctx;
isize scope_index;
isize uses;
};
enum lbParamPasskind {