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Simplify copy elision on variable declarations

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gingerBill
2023-03-16 17:24:29 +00:00
parent 74fb74d9cb
commit bfb231fb8a
3 changed files with 34 additions and 40 deletions
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2
src/llvm_backend.hpp
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@@ -337,8 +337,6 @@ struct lbProcedure {
LLVMMetadataRef debug_info;
lbAddr current_elision_hint;
PtrMap<Ast *, lbValue> selector_values;
PtrMap<Ast *, lbAddr> selector_addr;
PtrMap<LLVMValueRef, lbTupleFix> tuple_fix_map;

8
src/llvm_backend_const.cpp
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@@ -485,13 +485,7 @@ gb_internal lbValue lb_const_value(lbModule *m, Type *type, ExactValue value, bo
LLVMValueRef ptr = LLVMBuildInBoundsGEP2(p->builder, llvm_type, array_data, indices, 2, "");
LLVMValueRef len = LLVMConstInt(lb_type(m, t_int), count, true);
lbAddr slice = {};
if (p->current_elision_hint.addr.value && are_types_identical(lb_addr_type(p->current_elision_hint), type)) {
slice = p->current_elision_hint;
p->current_elision_hint = {};
} else {
slice = lb_add_local_generated(p, type, false);
}
lbAddr slice = lb_add_local_generated(p, type, false);
map_set(&m->exact_value_compound_literal_addr_map, value.value_compound, slice);
lb_fill_slice(p, slice, {ptr, alloc_type_pointer(elem)}, {len, t_int});

64
src/llvm_backend_stmt.cpp
View File

@@ -2269,54 +2269,56 @@ gb_internal void lb_build_stmt(lbProcedure *p, Ast *node) {
return;
}
auto lvals = array_make<lbAddr>(permanent_allocator(), 0, vd->names.count);
for (Ast *name : vd->names) {
lbAddr lval = {};
if (!is_blank_ident(name)) {
Entity *e = entity_of_node(name);
// bool zero_init = true; // Always do it
bool zero_init = vd->values.count == 0;
lval = lb_add_local(p, e->type, e, zero_init);
}
array_add(&lvals, lval);
}
TEMPORARY_ALLOCATOR_GUARD();
auto const &values = vd->values;
if (values.count > 0) {
auto inits = array_make<lbValue>(permanent_allocator(), 0, lvals.count);
if (values.count == 0) {
auto lvals = slice_make<lbAddr>(temporary_allocator(), vd->names.count);
for_array(i, vd->names) {
Ast *name = vd->names[i];
if (!is_blank_ident(name)) {
Entity *e = entity_of_node(name);
// bool zero_init = true; // Always do it
bool zero_init = values.count == 0;
lvals[i] = lb_add_local(p, e->type, e, zero_init);
}
}
} else {
auto lvals_preused = slice_make<bool>(temporary_allocator(), vd->names.count);
auto lvals = slice_make<lbAddr>(temporary_allocator(), vd->names.count);
auto inits = array_make<lbValue>(temporary_allocator(), 0, lvals.count);
isize lval_index = 0;
for (Ast *rhs : values) {
p->current_elision_hint = lvals[lval_index];
rhs = unparen_expr(rhs);
lbValue init = lb_build_expr(p, rhs);
#if 1
if (p->current_elision_hint.addr.value != lvals[lval_index].addr.value) {
lvals[lval_index] = {}; // do nothing so that nothing will assign to it
} else {
if (rhs->kind == Ast_CompoundLit) {
// NOTE(bill, 2023-02-17): lb_const_value might produce a stack local variable for the
// compound literal, so reusing that variable should minimize the stack wastage
if (rhs->kind == Ast_CompoundLit) {
lbAddr *comp_lit_addr = map_get(&p->module->exact_value_compound_literal_addr_map, rhs);
if (comp_lit_addr) {
Entity *e = entity_of_node(vd->names[lval_index]);
if (e) {
GB_ASSERT(p->current_elision_hint.addr.value == nullptr);
GB_ASSERT(p->current_elision_hint.addr.value != lvals[lval_index].addr.value);
lvals[lval_index] = {}; // do nothing so that nothing will assign to it
}
lbAddr *comp_lit_addr = map_get(&p->module->exact_value_compound_literal_addr_map, rhs);
if (comp_lit_addr) {
if (Entity *e = entity_of_node(vd->names[lval_index])) {
lbValue val = comp_lit_addr->addr;
lb_add_entity(p->module, e, val);
lb_add_debug_local_variable(p, val.value, e->type, e->token);
lvals_preused[lval_index] = true;
}
}
}
#endif
lval_index += lb_append_tuple_values(p, &inits, init);
}
GB_ASSERT(lval_index == lvals.count);
p->current_elision_hint = {};
for_array(i, vd->names) {
Ast *name = vd->names[i];
if (!is_blank_ident(name) && !lvals_preused[i]) {
Entity *e = entity_of_node(name);
bool zero_init = values.count == 0;
lvals[i] = lb_add_local(p, e->type, e, zero_init);
}
}
GB_ASSERT(lvals.count == inits.count);
for_array(i, inits) {