auto merge of #5317 : luqmana/rust/inline-asm, r=graydon

```Rust
#[cfg(target_os = "macos")]
fn helloworld() {
    unsafe {
        asm!(".pushsection __RODATA, __rodata
                  msg: .asciz \"Hello World!\"
              .popsection
              movq msg@GOTPCREL(%rip), %rdi
              call _puts");
    }
}

#[cfg(target_os = "linux")]
fn helloworld() {
    unsafe {
        asm!(".pushsection .rodata
                  msg: .asciz \"Hello World!\"
              .popsection
              movq msg@GOTPCREL(%rip), %rdi
              call puts");
    }
}

fn main() {
    helloworld();
}
```

```
% rustc foo.rs
% ./foo
Hello World!
```

8 files changed, 195 insertions, 1 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 27dba9c2b5e..b22018c4c76 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -601,6 +601,9 @@ pub enum expr_ {
     expr_ret(Option<@expr>),
     expr_log(log_level, @expr, @expr),
 
+    /* asm, clobbers + constraints, volatile, align stack */
+    expr_inline_asm(@~str, @~str, bool, bool),
+
     expr_mac(mac),
 
     // A struct literal expression.
diff --git a/src/libsyntax/ext/asm.rs b/src/libsyntax/ext/asm.rs
new file mode 100644
index 00000000000..8051a67d8fd
--- /dev/null
+++ b/src/libsyntax/ext/asm.rs
@@ -0,0 +1,174 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+
+/*
+ * Inline assembly support.
+ */
+
+use core::prelude::*;
+
+use ast;
+use codemap::span;
+use ext::base;
+use ext::base::*;
+use parse;
+use parse::token;
+
+enum State {
+    Asm,
+    Outputs,
+    Inputs,
+    Clobbers,
+    Options
+}
+
+fn next_state(s: State) -> Option<State> {
+    match s {
+        Asm      => Some(Outputs),
+        Outputs  => Some(Inputs),
+        Inputs   => Some(Clobbers),
+        Clobbers => Some(Options),
+        Options  => None
+    }
+}
+
+pub fn expand_asm(cx: ext_ctxt, sp: span, tts: &[ast::token_tree])
+    -> base::MacResult {
+
+    let p = parse::new_parser_from_tts(cx.parse_sess(), cx.cfg(),
+                                       vec::from_slice(tts));
+
+    let mut asm = ~"";
+    let mut outputs = ~[];
+    let mut inputs = ~[];
+    let mut cons = ~"";
+    let mut volatile = false;
+    let mut alignstack = false;
+
+    let mut state = Asm;
+    loop outer: {
+        match state {
+            Asm => {
+                asm = expr_to_str(cx, p.parse_expr(),
+                                ~"inline assembly must be a string literal.");
+            }
+            Outputs => {
+                while *p.token != token::EOF &&
+                      *p.token != token::COLON &&
+                      *p.token != token::MOD_SEP {
+
+                    if outputs.len() != 0 {
+                        p.eat(&token::COMMA);
+                    }
+
+                    let constraint = p.parse_str();
+                    p.expect(&token::LPAREN);
+                    let out = p.parse_expr();
+                    p.expect(&token::RPAREN);
+
+                    outputs.push((constraint, out));
+                }
+            }
+            Inputs => {
+                while *p.token != token::EOF &&
+                      *p.token != token::COLON &&
+                      *p.token != token::MOD_SEP {
+
+                    if inputs.len() != 0 {
+                        p.eat(&token::COMMA);
+                    }
+
+                    let constraint = p.parse_str();
+                    p.expect(&token::LPAREN);
+                    let in = p.parse_expr();
+                    p.expect(&token::RPAREN);
+
+                    inputs.push((constraint, in));
+                }
+            }
+            Clobbers => {
+                let mut clobs = ~[];
+                while *p.token != token::EOF &&
+                      *p.token != token::COLON &&
+                      *p.token != token::MOD_SEP {
+
+                    if clobs.len() != 0 {
+                        p.eat(&token::COMMA);
+                    }
+
+                    let clob = ~"~{" + *p.parse_str() + ~"}";
+                    clobs.push(clob);
+                }
+
+                cons = str::connect(clobs, ",");
+            }
+            Options => {
+                let option = *p.parse_str();
+
+                if option == ~"volatile" {
+                    volatile = true;
+                } else if option == ~"alignstack" {
+                    alignstack = true;
+                }
+
+                if *p.token == token::COMMA {
+                    p.eat(&token::COMMA);
+                }
+            }
+        }
+
+        while *p.token == token::COLON   ||
+              *p.token == token::MOD_SEP ||
+              *p.token == token::EOF {
+            state = if *p.token == token::COLON {
+                p.bump();
+                match next_state(state) {
+                    Some(x) => x,
+                    None    => break outer
+                }
+            } else if *p.token == token::MOD_SEP {
+                p.bump();
+                let s = match next_state(state) {
+                    Some(x) => x,
+                    None    => break outer
+                };
+                match next_state(s) {
+                    Some(x) => x,
+                    None    => break outer
+                }
+            } else if *p.token == token::EOF {
+                break outer;
+            } else {
+               state
+            };
+        }
+    }
+
+    MRExpr(@ast::expr {
+        id: cx.next_id(),
+        callee_id: cx.next_id(),
+        node: ast::expr_inline_asm(@asm, @cons, volatile, alignstack),
+        span: sp
+    })
+}
+
+
+
+//
+// Local Variables:
+// mode: rust
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// End:
+//
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 23cabc09946..1eae4b84cc9 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -198,6 +198,8 @@ pub fn syntax_expander_table() -> SyntaxEnv {
                                 ext::source_util::expand_mod));
     syntax_expanders.insert(@~"proto",
                             builtin_item_tt(ext::pipes::expand_proto));
+    syntax_expanders.insert(@~"asm",
+                            builtin_normal_tt(ext::asm::expand_asm));
     syntax_expanders.insert(
         @~"trace_macros",
         builtin_normal_tt(ext::trace_macros::expand_trace_macros));
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 427760c920f..15097f57b02 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -560,6 +560,7 @@ pub fn noop_fold_expr(e: &expr_, fld: @ast_fold) -> expr_ {
                 fld.fold_expr(e)
             )
         }
+        expr_inline_asm(*) => copy *e,
         expr_mac(ref mac) => expr_mac(fold_mac((*mac))),
         expr_struct(path, ref fields, maybe_expr) => {
             expr_struct(
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 99c1c2cb1fe..51e36d9ec02 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -27,7 +27,7 @@ use ast::{expr_field, expr_fn_block, expr_if, expr_index};
 use ast::{expr_lit, expr_log, expr_loop, expr_loop_body, expr_mac};
 use ast::{expr_method_call, expr_paren, expr_path, expr_repeat};
 use ast::{expr_ret, expr_swap, expr_struct, expr_tup, expr_unary};
-use ast::{expr_vec, expr_vstore, expr_vstore_mut_box};
+use ast::{expr_vec, expr_vstore, expr_vstore_mut_box, expr_inline_asm};
 use ast::{expr_vstore_fixed, expr_vstore_slice, expr_vstore_box};
 use ast::{expr_vstore_mut_slice, expr_while, extern_fn, field, fn_decl};
 use ast::{expr_vstore_uniq, TyClosure, TyBareFn, Onceness, Once, Many};
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 62f593f15c1..92883123782 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1398,6 +1398,18 @@ pub fn print_expr(s: @ps, &&expr: @ast::expr) {
           }
         }
       }
+      ast::expr_inline_asm(a, c, v, _) => {
+        if v {
+            word(s.s, ~"__volatile__ asm!");
+        } else {
+            word(s.s, ~"asm!");
+        }
+        popen(s);
+        print_string(s, *a);
+        word_space(s, ~",");
+        print_string(s, *c);
+        pclose(s);
+      }
       ast::expr_mac(ref m) => print_mac(s, (*m)),
       ast::expr_paren(e) => {
           popen(s);
diff --git a/src/libsyntax/syntax.rc b/src/libsyntax/syntax.rc
index 7f84d6a3010..e13ef976d97 100644
--- a/src/libsyntax/syntax.rc
+++ b/src/libsyntax/syntax.rc
@@ -60,6 +60,7 @@ pub mod print {
 }
 
 pub mod ext {
+    pub mod asm;
     pub mod base;
     pub mod expand;
 
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index f04894729bd..95ab603f584 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -562,6 +562,7 @@ pub fn visit_expr<E>(ex: @expr, e: E, v: vt<E>) {
         }
         expr_mac(ref mac) => visit_mac((*mac), e, v),
         expr_paren(x) => (v.visit_expr)(x, e, v),
+        expr_inline_asm(*) => (),
     }
     (v.visit_expr_post)(ex, e, v);
 }