src/libsyntax_ext/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 // Inline assembly support.
  12 //
  13 use self::State::*;
  14
  15 use syntax::ast;
  16 use syntax::codemap;
  17 use syntax::ext::base;
  18 use syntax::ext::base::*;
  19 use syntax::feature_gate;
  20 use syntax::parse::token::intern;
  21 use syntax::parse::{self, token};
  22 use syntax::ptr::P;
  23 use syntax::ast::AsmDialect;
  24 use syntax_pos::Span;
  25 use syntax::tokenstream;
  26
  27 enum State {
  28     Asm,
  29     Outputs,
  30     Inputs,
  31     Clobbers,
  32     Options,
  33     StateNone,
  34 }
  35
  36 impl State {
  37     fn next(&self) -> State {
  38         match *self {
  39             Asm => Outputs,
  40             Outputs => Inputs,
  41             Inputs => Clobbers,
  42             Clobbers => Options,
  43             Options => StateNone,
  44             StateNone => StateNone,
  45         }
  46     }
  47 }
  48
  49 const OPTIONS: &'static [&'static str] = &["volatile", "alignstack", "intel"];
  50
  51 pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt,
  52                        sp: Span,
  53                        tts: &[tokenstream::TokenTree])
  54                        -> Box<base::MacResult + 'cx> {
  55     if !cx.ecfg.enable_asm() {
  56         feature_gate::emit_feature_err(&cx.parse_sess,
  57                                        "asm",
  58                                        sp,
  59                                        feature_gate::GateIssue::Language,
  60                                        feature_gate::EXPLAIN_ASM);
  61         return DummyResult::expr(sp);
  62     }
  63
  64     // Split the tts before the first colon, to avoid `asm!("x": y)`  being
  65     // parsed as `asm!(z)` with `z = "x": y` which is type ascription.
  66     let first_colon = tts.iter()
  67         .position(|tt| {
  68             match *tt {
  69                 tokenstream::TokenTree::Token(_, token::Colon) |
  70                 tokenstream::TokenTree::Token(_, token::ModSep) => true,
  71                 _ => false,
  72             }
  73         })
  74         .unwrap_or(tts.len());
  75     let mut p = cx.new_parser_from_tts(&tts[first_colon..]);
  76     let mut asm = token::InternedString::new("");
  77     let mut asm_str_style = None;
  78     let mut outputs = Vec::new();
  79     let mut inputs = Vec::new();
  80     let mut clobs = Vec::new();
  81     let mut volatile = false;
  82     let mut alignstack = false;
  83     let mut dialect = AsmDialect::Att;
  84
  85     let mut state = Asm;
  86
  87     'statement: loop {
  88         match state {
  89             Asm => {
  90                 if asm_str_style.is_some() {
  91                     // If we already have a string with instructions,
  92                     // ending up in Asm state again is an error.
  93                     cx.span_err(sp, "malformed inline assembly");
  94                     return DummyResult::expr(sp);
  95                 }
  96                 // Nested parser, stop before the first colon (see above).
  97                 let mut p2 = cx.new_parser_from_tts(&tts[..first_colon]);
  98                 let (s, style) = match expr_to_string(cx,
  99                                                       panictry!(p2.parse_expr()),
 100                                                       "inline assembly must be a string literal") {
 101                     Some((s, st)) => (s, st),
 102                     // let compilation continue
 103                     None => return DummyResult::expr(sp),
 104                 };
 105
 106                 // This is most likely malformed.
 107                 if p2.token != token::Eof {
 108                     let mut extra_tts = panictry!(p2.parse_all_token_trees());
 109                     extra_tts.extend(tts[first_colon..].iter().cloned());
 110                     p = parse::tts_to_parser(cx.parse_sess, extra_tts, cx.cfg());
 111                 }
 112
 113                 asm = s;
 114                 asm_str_style = Some(style);
 115             }
 116             Outputs => {
 117                 while p.token != token::Eof && p.token != token::Colon && p.token != token::ModSep {
 118
 119                     if !outputs.is_empty() {
 120                         p.eat(&token::Comma);
 121                     }
 122
 123                     let (constraint, _str_style) = panictry!(p.parse_str());
 124
 125                     let span = p.last_span;
 126
 127                     panictry!(p.expect(&token::OpenDelim(token::Paren)));
 128                     let out = panictry!(p.parse_expr());
 129                     panictry!(p.expect(&token::CloseDelim(token::Paren)));
 130
 131                     // Expands a read+write operand into two operands.
 132                     //
 133                     // Use '+' modifier when you want the same expression
 134                     // to be both an input and an output at the same time.
 135                     // It's the opposite of '=&' which means that the memory
 136                     // cannot be shared with any other operand (usually when
 137                     // a register is clobbered early.)
 138                     let mut ch = constraint.chars();
 139                     let output = match ch.next() {
 140                         Some('=') => None,
 141                         Some('+') => {
 142                             Some(token::intern_and_get_ident(&format!("={}", ch.as_str())))
 143                         }
 144                         _ => {
 145                             cx.span_err(span, "output operand constraint lacks '=' or '+'");
 146                             None
 147                         }
 148                     };
 149
 150                     let is_rw = output.is_some();
 151                     let is_indirect = constraint.contains("*");
 152                     outputs.push(ast::InlineAsmOutput {
 153                         constraint: output.unwrap_or(constraint.clone()),
 154                         expr: out,
 155                         is_rw: is_rw,
 156                         is_indirect: is_indirect,
 157                     });
 158                 }
 159             }
 160             Inputs => {
 161                 while p.token != token::Eof && p.token != token::Colon && p.token != token::ModSep {
 162
 163                     if !inputs.is_empty() {
 164                         p.eat(&token::Comma);
 165                     }
 166
 167                     let (constraint, _str_style) = panictry!(p.parse_str());
 168
 169                     if constraint.starts_with("=") {
 170                         cx.span_err(p.last_span, "input operand constraint contains '='");
 171                     } else if constraint.starts_with("+") {
 172                         cx.span_err(p.last_span, "input operand constraint contains '+'");
 173                     }
 174
 175                     panictry!(p.expect(&token::OpenDelim(token::Paren)));
 176                     let input = panictry!(p.parse_expr());
 177                     panictry!(p.expect(&token::CloseDelim(token::Paren)));
 178
 179                     inputs.push((constraint, input));
 180                 }
 181             }
 182             Clobbers => {
 183                 while p.token != token::Eof && p.token != token::Colon && p.token != token::ModSep {
 184
 185                     if !clobs.is_empty() {
 186                         p.eat(&token::Comma);
 187                     }
 188
 189                     let (s, _str_style) = panictry!(p.parse_str());
 190
 191                     if OPTIONS.iter().any(|&opt| s == opt) {
 192                         cx.span_warn(p.last_span, "expected a clobber, found an option");
 193                     } else if s.starts_with("{") || s.ends_with("}") {
 194                         cx.span_err(p.last_span, "clobber should not be surrounded by braces");
 195                     }
 196
 197                     clobs.push(s);
 198                 }
 199             }
 200             Options => {
 201                 let (option, _str_style) = panictry!(p.parse_str());
 202
 203                 if option == "volatile" {
 204                     // Indicates that the inline assembly has side effects
 205                     // and must not be optimized out along with its outputs.
 206                     volatile = true;
 207                 } else if option == "alignstack" {
 208                     alignstack = true;
 209                 } else if option == "intel" {
 210                     dialect = AsmDialect::Intel;
 211                 } else {
 212                     cx.span_warn(p.last_span, "unrecognized option");
 213                 }
 214
 215                 if p.token == token::Comma {
 216                     p.eat(&token::Comma);
 217                 }
 218             }
 219             StateNone => (),
 220         }
 221
 222         loop {
 223             // MOD_SEP is a double colon '::' without space in between.
 224             // When encountered, the state must be advanced twice.
 225             match (&p.token, state.next(), state.next().next()) {
 226                 (&token::Colon, StateNone, _) |
 227                 (&token::ModSep, _, StateNone) => {
 228                     p.bump();
 229                     break 'statement;
 230                 }
 231                 (&token::Colon, st, _) |
 232                 (&token::ModSep, _, st) => {
 233                     p.bump();
 234                     state = st;
 235                 }
 236                 (&token::Eof, ..) => break 'statement,
 237                 _ => break,
 238             }
 239         }
 240     }
 241
 242     let expn_id = cx.codemap().record_expansion(codemap::ExpnInfo {
 243         call_site: sp,
 244         callee: codemap::NameAndSpan {
 245             format: codemap::MacroBang(intern("asm")),
 246             span: None,
 247             allow_internal_unstable: false,
 248         },
 249     });
 250
 251     MacEager::expr(P(ast::Expr {
 252         id: ast::DUMMY_NODE_ID,
 253         node: ast::ExprKind::InlineAsm(ast::InlineAsm {
 254             asm: token::intern_and_get_ident(&asm),
 255             asm_str_style: asm_str_style.unwrap(),
 256             outputs: outputs,
 257             inputs: inputs,
 258             clobbers: clobs,
 259             volatile: volatile,
 260             alignstack: alignstack,
 261             dialect: dialect,
 262             expn_id: expn_id,
 263         }),
 264         span: sp,
 265         attrs: ast::ThinVec::new(),
 266     }))
 267 }