src/libsyntax_ext/global_asm.rs

   1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 /// Module-level assembly support.
  12 ///
  13 /// The macro defined here allows you to specify "top-level",
  14 /// "file-scoped", or "module-level" assembly. These synonyms
  15 /// all correspond to LLVM's module-level inline assembly instruction.
  16 ///
  17 /// For example, `global_asm!("some assembly here")` codegens to
  18 /// LLVM's `module asm "some assembly here"`. All of LLVM's caveats
  19 /// therefore apply.
  20
  21 use rustc_data_structures::small_vec::OneVector;
  22
  23 use syntax::ast;
  24 use syntax::codemap::respan;
  25 use syntax::ext::base;
  26 use syntax::ext::base::*;
  27 use syntax::feature_gate;
  28 use syntax::ptr::P;
  29 use syntax::symbol::Symbol;
  30 use syntax_pos::Span;
  31 use syntax::tokenstream;
  32
  33 pub const MACRO: &'static str = "global_asm";
  34
  35 pub fn expand_global_asm<'cx>(cx: &'cx mut ExtCtxt,
  36                               sp: Span,
  37                               tts: &[tokenstream::TokenTree]) -> Box<dyn base::MacResult + 'cx> {
  38     if !cx.ecfg.enable_global_asm() {
  39         feature_gate::emit_feature_err(&cx.parse_sess,
  40                                        MACRO,
  41                                        sp,
  42                                        feature_gate::GateIssue::Language,
  43                                        feature_gate::EXPLAIN_GLOBAL_ASM);
  44         return DummyResult::any(sp);
  45     }
  46
  47     let mut p = cx.new_parser_from_tts(tts);
  48     let (asm, _) = match expr_to_string(cx,
  49                                         panictry!(p.parse_expr()),
  50                                         "inline assembly must be a string literal") {
  51         Some((s, st)) => (s, st),
  52         None => return DummyResult::any(sp),
  53     };
  54
  55     MacEager::items(OneVector::one(P(ast::Item {
  56         ident: ast::Ident::with_empty_ctxt(Symbol::intern("")),
  57         attrs: Vec::new(),
  58         id: ast::DUMMY_NODE_ID,
  59         node: ast::ItemKind::GlobalAsm(P(ast::GlobalAsm {
  60             asm,
  61             ctxt: cx.backtrace(),
  62         })),
  63         vis: respan(sp.shrink_to_lo(), ast::VisibilityKind::Inherited),
  64         span: sp,
  65         tokens: None,
  66     })))
  67 }