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Use an if-else chain for a type switch on any #5952

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Use an if-else chain for a type switch on any #5952

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7a77581
Use an if-else chain for a type switch on `any`
gingerBill Nov 22, 2025
c9f69aa
Improve the logic
gingerBill Nov 22, 2025
a2b0244
Only do the if-else chain for type switch on wasm targets
gingerBill Nov 22, 2025
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87 changes: 73 additions & 14 deletions src/llvm_backend_stmt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1950,19 +1950,29 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
GB_PANIC("Unknown switch kind");
}

if (tag.value != nullptr) {
String tag_name = str_lit("typeswitch.tag");
LLVMSetValueName2(tag.value, cast(char const *)tag_name.text, tag_name.len);
}

ast_node(body, BlockStmt, ss->body);

lbBlock *done = lb_create_block(p, "typeswitch.done");
lbBlock *else_block = done;
lbBlock *default_block = nullptr;
isize num_cases = 0;

for (Ast *clause : body->stmts) {
auto body_blocks = slice_make<lbBlock *>(permanent_allocator(), body->stmts.count);
for_array(i, body->stmts) {
Ast *clause = body->stmts[i];
ast_node(cc, CaseClause, clause);
num_cases += cc->list.count;

body_blocks[i] = lb_create_block(p, cc->list.count == 0 ? "typeswitch.default.body" : "typeswitch.case.body");

if (cc->list.count == 0) {
GB_ASSERT(default_block == nullptr);
default_block = lb_create_block(p, "typeswitch.default.body");
default_block = body_blocks[i];
else_block = default_block;
}
}
Expand All @@ -1974,7 +1984,11 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
switch_instr = LLVMBuildSwitch(p->builder, lb_const_bool(p->module, t_llvm_bool, false).value, else_block->block, cast(unsigned)num_cases);
} else {
GB_ASSERT(tag.value != nullptr);
switch_instr = LLVMBuildSwitch(p->builder, tag.value, else_block->block, cast(unsigned)num_cases);
if (switch_kind == TypeSwitch_Any && is_arch_wasm()) {
// Only do the if-else chain on wasm targets
} else {
switch_instr = LLVMBuildSwitch(p->builder, tag.value, else_block->block, cast(unsigned)num_cases);
}
}

bool all_by_reference = false;
Expand Down Expand Up @@ -2025,30 +2039,42 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
}
lbValue backing_ptr = backing_data.addr;

for (Ast *clause : body->stmts) {

Ast *default_clause = nullptr;

for_array(i, body->stmts) {
Ast *clause = body->stmts[i];
ast_node(cc, CaseClause, clause);

Entity *case_entity = implicit_entity_of_node(clause);
lb_open_scope(p, cc->scope);

if (cc->list.count == 0) {
lb_start_block(p, default_block);
if (case_entity->flags & EntityFlag_Value) {
lb_store_type_case_implicit(p, clause, parent_value, true);
} else {
lb_store_type_case_implicit(p, clause, parent_ptr, true);
default_clause = clause;
if (switch_instr != nullptr) {
lb_open_scope(p, cc->scope);

lb_start_block(p, default_block);
if (case_entity->flags & EntityFlag_Value) {
lb_store_type_case_implicit(p, clause, parent_value, true);
} else {
lb_store_type_case_implicit(p, clause, parent_ptr, true);
}
lb_type_case_body(p, ss->label, clause, p->curr_block, done);
}
lb_type_case_body(p, ss->label, clause, p->curr_block, done);
continue;
}

lbBlock *body = lb_create_block(p, "typeswitch.body");
lb_open_scope(p, cc->scope);

lbBlock *body = body_blocks[i];
if (p->debug_info != nullptr) {
LLVMSetCurrentDebugLocation2(p->builder, lb_debug_location_from_ast(p, clause));
}

lbBlock *next_cond = nullptr;
bool saw_nil = false;
for (Ast *type_expr : cc->list) {
for_array(i, cc->list) {
Ast *type_expr = cc->list[i];
Type *case_type = type_of_expr(type_expr);
lbValue on_val = {};
if (switch_kind == TypeSwitch_Union) {
Expand All @@ -2064,7 +2090,17 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
}
}
GB_ASSERT(on_val.value != nullptr);
LLVMAddCase(switch_instr, on_val.value, body->block);

if (switch_instr != nullptr) {
LLVMAddCase(switch_instr, on_val.value, body->block);
continue;
}

lbValue cond = lb_emit_comp(p, Token_CmpEq, on_val, tag);

next_cond = lb_create_block(p, "typeswitch.case.next");
lb_emit_if(p, cond, body, next_cond);
lb_start_block(p, next_cond);
}


Expand Down Expand Up @@ -2111,6 +2147,29 @@ gb_internal void lb_build_type_switch_stmt(lbProcedure *p, AstTypeSwitchStmt *ss
}

lb_type_case_body(p, ss->label, clause, body, done);

if (next_cond != nullptr) {
GB_ASSERT(switch_instr == nullptr);
lb_start_block(p, next_cond);
}
}

if (default_block != nullptr && switch_instr == nullptr) {
GB_ASSERT(default_clause != nullptr);
lb_emit_jump(p, default_block);

Entity *case_entity = implicit_entity_of_node(default_clause);
ast_node(cc, CaseClause, default_clause);

lb_open_scope(p, cc->scope);

lb_start_block(p, else_block);
if (case_entity->flags & EntityFlag_Value) {
lb_store_type_case_implicit(p, default_clause, parent_value, true);
} else {
lb_store_type_case_implicit(p, default_clause, parent_ptr, true);
}
lb_type_case_body(p, ss->label, default_clause, p->curr_block, done);
}

lb_emit_jump(p, done);
Expand Down