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Improve code generation for type switch statements to use a jump table by default

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gingerBill
2021-06-09 23:46:00 +01:00
parent b0e21bd616
commit 82eae32bca
1 changed files with 38 additions and 29 deletions
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src/llvm_backend.cpp
+38 -29
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@@ -4882,7 +4882,7 @@ void lb_build_switch_stmt(lbProcedure *p, AstSwitchStmt *ss, Scope *scope) {
}
lbValue lhs = lb_build_expr(p, ie->left);
lbValue rhs = lb_build_expr(p, ie->right);
// TODO(bill): do short circuit here
lbValue cond_lhs = lb_emit_comp(p, Token_LtEq, lhs, tag);
lbValue cond_rhs = lb_emit_comp(p, op, tag, rhs);
cond = lb_emit_arith(p, Token_And, cond_lhs, cond_rhs, t_bool);
@@ -5001,29 +5001,45 @@ void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss) {
parent_ptr = lb_address_from_load_or_generate_local(p, parent);
}
lbValue tag_index = {};
lbValue tag = {};
lbValue union_data = {};
if (switch_kind == TypeSwitch_Union) {
union_data = lb_emit_conv(p, parent_ptr, t_rawptr);
if (is_type_union_maybe_pointer(type_deref(parent_ptr.type))) {
tag_index = lb_emit_conv(p, lb_emit_comp_against_nil(p, Token_NotEq, union_data), t_int);
tag = lb_emit_conv(p, lb_emit_comp_against_nil(p, Token_NotEq, union_data), t_int);
} else {
lbValue tag_ptr = lb_emit_union_tag_ptr(p, parent_ptr);
tag_index = lb_emit_load(p, tag_ptr);
tag = lb_emit_load(p, tag_ptr);
}
} else if (switch_kind == TypeSwitch_Any) {
tag = lb_emit_load(p, lb_emit_struct_ep(p, parent_ptr, 1));
} else {
GB_PANIC("Unknown switch kind");
}
lbBlock *start_block = lb_create_block(p, "typeswitch.case.first");
lb_emit_jump(p, start_block);
lb_start_block(p, start_block);
// NOTE(bill): Append this later
lbBlock *done = lb_create_block(p, "typeswitch.done");
Ast *default_ = nullptr;
ast_node(body, BlockStmt, ss->body);
gb_local_persist i32 weird_count = 0;
lbBlock *done = lb_create_block(p, "typeswitch.done");
lbBlock *else_block = done;
lbBlock *default_block = nullptr;
isize num_cases = 0;
for_array(i, body->stmts) {
Ast *clause = body->stmts[i];
ast_node(cc, CaseClause, clause);
num_cases += cc->list.count;
if (cc->list.count == 0) {
GB_ASSERT(default_block == nullptr);
default_block = lb_create_block(p, "typeswitch.default.body");
else_block = default_block;
}
}
GB_ASSERT(tag.value != nullptr);
LLVMValueRef switch_instr = LLVMBuildSwitch(p->builder, tag.value, else_block->block, cast(unsigned)num_cases);
// NOTE(bill): Append this later
Ast *default_ = nullptr;
for_array(i, body->stmts) {
Ast *clause = body->stmts[i];
@@ -5034,25 +5050,19 @@ void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss) {
}
lbBlock *body = lb_create_block(p, "typeswitch.body");
lbBlock *next = nullptr;
Type *case_type = nullptr;
for_array(type_index, cc->list) {
next = lb_create_block(p, "typeswitch.next");
case_type = type_of_expr(cc->list[type_index]);
lbValue cond = {};
lbValue on_val = {};
if (switch_kind == TypeSwitch_Union) {
Type *ut = base_type(type_deref(parent.type));
lbValue variant_tag = lb_const_union_tag(m, ut, case_type);
cond = lb_emit_comp(p, Token_CmpEq, tag_index, variant_tag);
} else if (switch_kind == TypeSwitch_Any) {
lbValue any_typeid = lb_emit_load(p, lb_emit_struct_ep(p, parent_ptr, 1));
lbValue case_typeid = lb_typeid(m, case_type);
cond = lb_emit_comp(p, Token_CmpEq, any_typeid, case_typeid);
}
GB_ASSERT(cond.value != nullptr);
on_val = lb_const_union_tag(m, ut, case_type);
lb_emit_if(p, cond, body, next);
lb_start_block(p, next);
} else if (switch_kind == TypeSwitch_Any) {
on_val = lb_typeid(m, case_type);
}
GB_ASSERT(on_val.value != nullptr);
LLVMAddCase(switch_instr, on_val.value, body->block);
}
Entity *case_entity = implicit_entity_of_node(clause);
@@ -5068,8 +5078,7 @@ void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss) {
if (switch_kind == TypeSwitch_Union) {
data = union_data;
} else if (switch_kind == TypeSwitch_Any) {
lbValue any_data = lb_emit_load(p, lb_emit_struct_ep(p, parent_ptr, 0));
data = any_data;
data = lb_emit_load(p, lb_emit_struct_ep(p, parent_ptr, 0));
}
Type *ct = case_entity->type;
@@ -5083,10 +5092,10 @@ void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss) {
lb_store_type_case_implicit(p, clause, value);
lb_type_case_body(p, ss->label, clause, body, done);
lb_start_block(p, next);
}
if (default_ != nullptr) {
lb_start_block(p, default_block);
lb_store_type_case_implicit(p, default_, parent_value);
lb_type_case_body(p, ss->label, default_, p->curr_block, done);
} else {