Use a cache when generating the map header to minimize stack wastage

src/llvm_backend.cpp

@@ -502,48 +502,58 @@ lbValue lb_generate_anonymous_proc_lit(lbModule *m, String const &prefix_name, A
 
 lbValue lb_gen_map_header(lbProcedure *p, lbValue map_val_ptr, Type *map_type) {
 	GB_ASSERT_MSG(is_type_pointer(map_val_ptr.type), "%s", type_to_string(map_val_ptr.type));
-	lbAddr h = lb_add_local_generated(p, t_map_header, false); // all the values will be initialzed later
 	map_type = base_type(map_type);
 	GB_ASSERT(map_type->kind == Type_Map);
 
-	Type *key_type = map_type->Map.key;
-	Type *val_type = map_type->Map.value;
-	gb_unused(val_type);
+	lbAddr h = {};
+	lbAddr *found = map_get(&p->map_header_cache, map_val_ptr.value);
+	if (found != nullptr) {
+		h = *found;
+	} else {
+		h = lb_add_local_generated(p, t_map_header, false); // all the values will be initialzed later
 
-	GB_ASSERT(map_type->Map.entry_type->kind == Type_Struct);
-	map_type->Map.entry_type->cached_size = -1;
-	map_type->Map.entry_type->Struct.are_offsets_set = false;
-	
-	i64 entry_size   = type_size_of  (map_type->Map.entry_type);
-	i64 entry_align  = type_align_of (map_type->Map.entry_type);
-	
-	i64 key_offset = type_offset_of(map_type->Map.entry_type, 2);
-	i64 key_size   = type_size_of  (map_type->Map.key);
+		Type *key_type = map_type->Map.key;
+		Type *val_type = map_type->Map.value;
+		gb_unused(val_type);
 
-	i64 value_offset = type_offset_of(map_type->Map.entry_type, 3);
-	i64 value_size   = type_size_of  (map_type->Map.value);
-	
-	
-	Type *map_header_base = base_type(t_map_header);
-	GB_ASSERT(map_header_base->Struct.fields.count == 8);
-	Type *raw_map_ptr_type = map_header_base->Struct.fields[0]->type;
-	LLVMValueRef const_values[8] = {};
-	const_values[0] = LLVMConstNull(lb_type(p->module, raw_map_ptr_type));
-	const_values[1] = lb_get_equal_proc_for_type(p->module, key_type)    .value;
-	const_values[2] = lb_const_int(p->module, t_int,        entry_size)  .value;
-	const_values[3] = lb_const_int(p->module, t_int,        entry_align) .value;
-	const_values[4] = lb_const_int(p->module, t_uintptr,    key_offset)  .value;
-	const_values[5] = lb_const_int(p->module, t_int,        key_size)    .value;
-	const_values[6] = lb_const_int(p->module, t_uintptr,    value_offset).value;
-	const_values[7] = lb_const_int(p->module, t_int,        value_size)  .value;
-	
-	LLVMValueRef const_value = llvm_const_named_struct(p->module, t_map_header, const_values, gb_count_of(const_values));
-	LLVMBuildStore(p->builder, const_value, h.addr.value);
-	
-	// NOTE(bill): Removes unnecessary allocation if split gep
-	lbValue gep0 = lb_emit_struct_ep(p, h.addr, 0);
-	lbValue m = lb_emit_conv(p, map_val_ptr, type_deref(gep0.type));
-	lb_emit_store(p, gep0, m);
+		GB_ASSERT(map_type->Map.entry_type->kind == Type_Struct);
+		map_type->Map.entry_type->cached_size = -1;
+		map_type->Map.entry_type->Struct.are_offsets_set = false;
+
+		i64 entry_size   = type_size_of  (map_type->Map.entry_type);
+		i64 entry_align  = type_align_of (map_type->Map.entry_type);
+
+		i64 key_offset = type_offset_of(map_type->Map.entry_type, 2);
+		i64 key_size   = type_size_of  (map_type->Map.key);
+
+		i64 value_offset = type_offset_of(map_type->Map.entry_type, 3);
+		i64 value_size   = type_size_of  (map_type->Map.value);
+
+
+		Type *map_header_base = base_type(t_map_header);
+		GB_ASSERT(map_header_base->Struct.fields.count == 8);
+		Type *raw_map_ptr_type = map_header_base->Struct.fields[0]->type;
+		LLVMValueRef const_values[8] = {};
+		const_values[0] = LLVMConstNull(lb_type(p->module, raw_map_ptr_type));
+		const_values[1] = lb_get_equal_proc_for_type(p->module, key_type)    .value;
+		const_values[2] = lb_const_int(p->module, t_int,        entry_size)  .value;
+		const_values[3] = lb_const_int(p->module, t_int,        entry_align) .value;
+		const_values[4] = lb_const_int(p->module, t_uintptr,    key_offset)  .value;
+		const_values[5] = lb_const_int(p->module, t_int,        key_size)    .value;
+		const_values[6] = lb_const_int(p->module, t_uintptr,    value_offset).value;
+		const_values[7] = lb_const_int(p->module, t_int,        value_size)  .value;
+
+		LLVMValueRef const_value = llvm_const_named_struct(p->module, t_map_header, const_values, gb_count_of(const_values));
+		LLVMBuildStore(p->builder, const_value, h.addr.value);
+
+		// NOTE(bill): Removes unnecessary allocation if split gep
+		lbValue gep0 = lb_emit_struct_ep(p, h.addr, 0);
+		lbValue m = lb_emit_conv(p, map_val_ptr, type_deref(gep0.type));
+		lb_emit_store(p, gep0, m);
+
+
+		map_set(&p->map_header_cache, map_val_ptr.value, h);
+	}
 
 	return lb_addr_load(p, h);
 }

src/llvm_backend.hpp

@@ -308,6 +308,7 @@ struct lbProcedure {
 
 	PtrMap<Ast *, lbValue> selector_values;
 	PtrMap<Ast *, lbAddr>  selector_addr;
+	PtrMap<LLVMValueRef, lbAddr> map_header_cache;
 };
 
 

src/llvm_backend_proc.cpp

@@ -121,8 +121,9 @@ lbProcedure *lb_create_procedure(lbModule *m, Entity *entity, bool ignore_body)
 	p->branch_blocks.allocator = a;
 	p->context_stack.allocator = a;
 	p->scope_stack.allocator   = a;
-	map_init(&p->selector_values, a, 0);
-	map_init(&p->selector_addr,   a, 0);
+	map_init(&p->selector_values,  a, 0);
+	map_init(&p->selector_addr,    a, 0);
+	map_init(&p->map_header_cache, a, 0);
 
 	if (p->is_foreign) {
 		lb_add_foreign_library_path(p->module, entity->Procedure.foreign_library);