bjoernager/rust
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Use ZST for fmt unsafety

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This allows the format_args! macro to keep the pre-expansion code out of
the unsafe block without doing gymnastics with nested `match`
expressions. This reduces codegen.
This commit is contained in:
Cameron Steffen 2021-09-21 00:56:45 -05:00
parent db1fb85cff
commit 09b37d7433
8 changed files with 108 additions and 100 deletions
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32
compiler/rustc_builtin_macros/src/format.rs
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@ -845,8 +845,7 @@ impl<'a, 'b> Context<'a, 'b> {
self.ecx.expr_match(self.macsp, head, vec![arm])
};
let ident = Ident::from_str_and_span("args", self.macsp);
let args_slice = self.ecx.expr_ident(self.macsp, ident);
let args_slice = self.ecx.expr_addr_of(self.macsp, args_match);
// Now create the fmt::Arguments struct with all our locals we created.
let (fn_name, fn_args) = if self.all_pieces_simple {
@ -856,25 +855,22 @@ impl<'a, 'b> Context<'a, 'b> {
// nonstandard placeholders, if there are any.
let fmt = self.ecx.expr_vec_slice(self.macsp, self.pieces);
("new_v1_formatted", vec![pieces, args_slice, fmt])
let path = self.ecx.std_path(&[sym::fmt, sym::UnsafeArg, sym::new]);
let unsafe_arg = self.ecx.expr_call_global(self.macsp, path, Vec::new());
let unsafe_expr = self.ecx.expr_block(P(ast::Block {
stmts: vec![self.ecx.stmt_expr(unsafe_arg)],
id: ast::DUMMY_NODE_ID,
rules: BlockCheckMode::Unsafe(UnsafeSource::CompilerGenerated),
span: self.macsp,
tokens: None,
could_be_bare_literal: false,
}));
("new_v1_formatted", vec![pieces, args_slice, fmt, unsafe_expr])
};
let path = self.ecx.std_path(&[sym::fmt, sym::Arguments, Symbol::intern(fn_name)]);
let arguments = self.ecx.expr_call_global(self.macsp, path, fn_args);
let body = self.ecx.expr_block(P(ast::Block {
stmts: vec![self.ecx.stmt_expr(arguments)],
id: ast::DUMMY_NODE_ID,
rules: BlockCheckMode::Unsafe(UnsafeSource::CompilerGenerated),
span: self.macsp,
tokens: None,
could_be_bare_literal: false,
}));
let ident = Ident::from_str_and_span("args", self.macsp);
let binding_mode = ast::BindingMode::ByRef(ast::Mutability::Not);
let pat = self.ecx.pat_ident_binding_mode(self.macsp, ident, binding_mode);
let arm = self.ecx.arm(self.macsp, pat, body);
self.ecx.expr_match(self.macsp, args_match, vec![arm])
self.ecx.expr_call_global(self.macsp, path, fn_args)
}
fn format_arg(