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Manually implement tail-recursion for parse_if_stmt

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gingerBill
2024-08-24 13:16:55 +01:00
parent a4cc207022
commit b6d9a0c32e
2 changed files with 20 additions and 12 deletions
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30
src/parser.cpp
View File

@@ -4532,12 +4532,10 @@ gb_internal Ast *parse_if_stmt(AstFile *f) {
return ast_bad_stmt(f, f->curr_token, f->curr_token);
}
if (f->recursion_depth_else_if > 256) {
syntax_error(f->curr_token, "if-else chain recursion depth limit hit. Consider using a 'switch' statement instead or refactor the code to not require a large if-else chain");
f->recursion_depth_else_if = 0;
return ast_bad_stmt(f, f->curr_token, f->curr_token);
}
Ast *top_if_stmt = nullptr;
Ast *prev_if_stmt = nullptr;
if_else_chain:;
Token token = expect_token(f, Token_if);
Ast *init = nullptr;
Ast *cond = nullptr;
@@ -4579,14 +4577,24 @@ gb_internal Ast *parse_if_stmt(AstFile *f) {
ignore_strict_style = true;
}
skip_possible_newline_for_literal(f, ignore_strict_style);
Ast *curr_if_stmt = ast_if_stmt(f, token, init, cond, body, nullptr);
if (top_if_stmt == nullptr) {
top_if_stmt = curr_if_stmt;
}
if (prev_if_stmt != nullptr) {
prev_if_stmt->IfStmt.else_stmt = curr_if_stmt;
}
if (f->curr_token.kind == Token_else) {
Token else_token = expect_token(f, Token_else);
switch (f->curr_token.kind) {
case Token_if:
f->recursion_depth_else_if += 1;
else_stmt = parse_if_stmt(f);
f->recursion_depth_else_if -= 1;
break;
// NOTE(bill): Instead of relying on recursive descent for an if-else chain
// we can just inline the tail-recursion manually with a simple loop like
// construct using a `goto`
prev_if_stmt = curr_if_stmt;
goto if_else_chain;
case Token_OpenBrace:
else_stmt = parse_block_stmt(f, false);
break;
@@ -4601,7 +4609,9 @@ gb_internal Ast *parse_if_stmt(AstFile *f) {
}
}
return ast_if_stmt(f, token, init, cond, body, else_stmt);
curr_if_stmt->IfStmt.else_stmt = else_stmt;
return top_if_stmt;
}
gb_internal Ast *parse_when_stmt(AstFile *f) {

2
src/parser.hpp
View File

@@ -120,8 +120,6 @@ struct AstFile {
bool allow_type;
bool in_when_statement;
isize recursion_depth_else_if;
isize total_file_decl_count;
isize delayed_decl_count;
Slice<Ast *> decls;