rust/src/librustc/middle/trans/foreign.rs

// 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.

use core::prelude::*;

use back::{link, abi};
use driver::session::arch_x86_64;
use driver::session::arch_arm;
use lib::llvm::{SequentiallyConsistent, Acquire, Release, Xchg};
use lib::llvm::{Struct, Array, ModuleRef, CallConv, Attribute};
use lib::llvm::{StructRetAttribute, ByValAttribute};
use lib::llvm::{llvm, TypeRef, ValueRef, Integer, Pointer, Float, Double};
use lib;
use middle::trans::base::*;
use middle::trans::cabi;
use middle::trans::cabi_x86_64::*;
use middle::trans::build::*;
use middle::trans::callee::*;
use middle::trans::common::*;
use middle::trans::datum::*;
use middle::trans::expr::{Dest, Ignore};
use middle::trans::glue;
use middle::trans::machine;
use middle::trans::shape;
use middle::trans::type_of::*;
use middle::trans::type_of;
use middle::ty::{FnTyBase, FnMeta, FnSig, arg};
use util::ppaux::ty_to_str;

use core::libc::c_uint;
use syntax::codemap::span;
use syntax::{ast, ast_util};
use syntax::{attr, ast_map};
use syntax::parse::token::special_idents;

export link_name, trans_foreign_mod, register_foreign_fn, trans_foreign_fn,
       trans_intrinsic;

fn abi_info(arch: session::arch) -> cabi::ABIInfo {
    return match arch {
        arch_x86_64 => x86_64_abi_info(),
        _ => cabi::llvm_abi_info()
    }
}

fn link_name(ccx: @crate_ctxt, i: @ast::foreign_item) -> ~str {
    match attr::first_attr_value_str_by_name(i.attrs, ~"link_name") {
        None => ccx.sess.str_of(i.ident),
        option::Some(ref ln) => (/*bad*/copy *ln)
    }
}

type c_stack_tys = {
    arg_tys: ~[TypeRef],
    ret_ty: TypeRef,
    ret_def: bool,
    bundle_ty: TypeRef,
    shim_fn_ty: TypeRef,
    fn_ty: cabi::FnType
};

fn c_arg_and_ret_lltys(ccx: @crate_ctxt,
                       id: ast::node_id) -> (~[TypeRef], TypeRef, ty::t) {
    match ty::get(ty::node_id_to_type(ccx.tcx, id)).sty {
        ty::ty_fn(ref fn_ty) => {
            let llargtys = type_of_explicit_args(
                ccx,
                /*bad*/copy fn_ty.sig.inputs);
            let llretty = type_of::type_of(ccx, fn_ty.sig.output);
            (llargtys, llretty, fn_ty.sig.output)
        }
        _ => ccx.sess.bug(~"c_arg_and_ret_lltys called on non-function type")
    }
}

fn c_stack_tys(ccx: @crate_ctxt,
               id: ast::node_id) -> @c_stack_tys {
    let (llargtys, llretty, ret_ty) = c_arg_and_ret_lltys(ccx, id);
    // XXX: Bad copy.
    let bundle_ty = T_struct(vec::append_one(copy llargtys, T_ptr(llretty)));
    let ret_def = !ty::type_is_bot(ret_ty) && !ty::type_is_nil(ret_ty);
    let fn_ty = abi_info(ccx.sess.targ_cfg.arch).
                    compute_info(llargtys, llretty, ret_def);
    return @{
        arg_tys: llargtys,
        ret_ty: llretty,
        ret_def: ret_def,
        bundle_ty: bundle_ty,
        shim_fn_ty: T_fn(~[T_ptr(bundle_ty)], T_void()),
        fn_ty: fn_ty
    };
}

type shim_arg_builder = fn(bcx: block, tys: @c_stack_tys,
                           llargbundle: ValueRef) -> ~[ValueRef];

type shim_ret_builder = fn(bcx: block, tys: @c_stack_tys,
                           llargbundle: ValueRef, llretval: ValueRef);

fn build_shim_fn_(ccx: @crate_ctxt,
                  +shim_name: ~str,
                  llbasefn: ValueRef,
                  tys: @c_stack_tys,
                  cc: lib::llvm::CallConv,
                  arg_builder: shim_arg_builder,
                  ret_builder: shim_ret_builder) -> ValueRef {

    let llshimfn = decl_internal_cdecl_fn(
        ccx.llmod, shim_name, tys.shim_fn_ty);

    // Declare the body of the shim function:
    let fcx = new_fn_ctxt(ccx, ~[], llshimfn, None);
    let bcx = top_scope_block(fcx, None);
    let lltop = bcx.llbb;
    let llargbundle = get_param(llshimfn, 0u);
    let llargvals = arg_builder(bcx, tys, llargbundle);

    // Create the call itself and store the return value:
    let llretval = CallWithConv(bcx, llbasefn,
                                llargvals, cc); // r

    ret_builder(bcx, tys, llargbundle, llretval);

    build_return(bcx);
    finish_fn(fcx, lltop);

    return llshimfn;
}

type wrap_arg_builder = fn(bcx: block, tys: @c_stack_tys,
                           llwrapfn: ValueRef,
                           llargbundle: ValueRef);

type wrap_ret_builder = fn(bcx: block, tys: @c_stack_tys,
                           llargbundle: ValueRef);

fn build_wrap_fn_(ccx: @crate_ctxt,
                  tys: @c_stack_tys,
                  llshimfn: ValueRef,
                  llwrapfn: ValueRef,
                  shim_upcall: ValueRef,
                  arg_builder: wrap_arg_builder,
                  ret_builder: wrap_ret_builder) {

    let _icx = ccx.insn_ctxt("foreign::build_wrap_fn_");
    let fcx = new_fn_ctxt(ccx, ~[], llwrapfn, None);
    let bcx = top_scope_block(fcx, None);
    let lltop = bcx.llbb;

    // Allocate the struct and write the arguments into it.
    let llargbundle = alloca(bcx, tys.bundle_ty);
    arg_builder(bcx, tys, llwrapfn, llargbundle);

    // Create call itself.
    let llshimfnptr = PointerCast(bcx, llshimfn, T_ptr(T_i8()));
    let llrawargbundle = PointerCast(bcx, llargbundle, T_ptr(T_i8()));
    Call(bcx, shim_upcall, ~[llrawargbundle, llshimfnptr]);
    ret_builder(bcx, tys, llargbundle);

    tie_up_header_blocks(fcx, lltop);

    // Make sure our standard return block (that we didn't use) is terminated
    let ret_cx = raw_block(fcx, false, fcx.llreturn);
    Unreachable(ret_cx);
}

// For each foreign function F, we generate a wrapper function W and a shim
// function S that all work together.  The wrapper function W is the function
// that other rust code actually invokes.  Its job is to marshall the
// arguments into a struct.  It then uses a small bit of assembly to switch
// over to the C stack and invoke the shim function.  The shim function S then
// unpacks the arguments from the struct and invokes the actual function F
// according to its specified calling convention.
//
// Example: Given a foreign c-stack function F(x: X, y: Y) -> Z,
// we generate a wrapper function W that looks like:
//
//    void W(Z* dest, void *env, X x, Y y) {
//        struct { X x; Y y; Z *z; } args = { x, y, z };
//        call_on_c_stack_shim(S, &args);
//    }
//
// The shim function S then looks something like:
//
//     void S(struct { X x; Y y; Z *z; } *args) {
//         *args->z = F(args->x, args->y);
//     }
//
// However, if the return type of F is dynamically sized or of aggregate type,
// the shim function looks like:
//
//     void S(struct { X x; Y y; Z *z; } *args) {
//         F(args->z, args->x, args->y);
//     }
//
// Note: on i386, the layout of the args struct is generally the same as the
// desired layout of the arguments on the C stack.  Therefore, we could use
// upcall_alloc_c_stack() to allocate the `args` structure and switch the
// stack pointer appropriately to avoid a round of copies.  (In fact, the shim
// function itself is unnecessary). We used to do this, in fact, and will
// perhaps do so in the future.
fn trans_foreign_mod(ccx: @crate_ctxt,
                    foreign_mod: ast::foreign_mod, abi: ast::foreign_abi) {

    let _icx = ccx.insn_ctxt("foreign::trans_foreign_mod");

    fn build_shim_fn(ccx: @crate_ctxt,
                     foreign_item: @ast::foreign_item,
                     tys: @c_stack_tys,
                     cc: lib::llvm::CallConv) -> ValueRef {

        let _icx = ccx.insn_ctxt("foreign::build_shim_fn");

        fn build_args(bcx: block, tys: @c_stack_tys,
                      llargbundle: ValueRef) -> ~[ValueRef] {
            let _icx = bcx.insn_ctxt("foreign::shim::build_args");
            return tys.fn_ty.build_shim_args(bcx, tys.arg_tys, llargbundle);
        }

        fn build_ret(bcx: block, tys: @c_stack_tys,
                     llargbundle: ValueRef, llretval: ValueRef)  {
            let _icx = bcx.insn_ctxt("foreign::shim::build_ret");
            tys.fn_ty.build_shim_ret(bcx, tys.arg_tys, tys.ret_def,
                                     llargbundle, llretval);
        }

        let lname = link_name(ccx, foreign_item);
        let llbasefn = base_fn(ccx, copy lname, tys, cc);
        // Name the shim function
        let shim_name = lname + ~"__c_stack_shim";
        return build_shim_fn_(ccx, shim_name, llbasefn, tys, cc,
                           build_args, build_ret);
    }

    fn base_fn(ccx: @crate_ctxt, +lname: ~str, tys: @c_stack_tys,
               cc: lib::llvm::CallConv) -> ValueRef {
        // Declare the "prototype" for the base function F:
        do tys.fn_ty.decl_fn |fnty| {
            decl_fn(ccx.llmod, /*bad*/copy lname, cc, fnty)
        }
    }

    // FIXME (#2535): this is very shaky and probably gets ABIs wrong all
    // over the place
    fn build_direct_fn(ccx: @crate_ctxt, decl: ValueRef,
                       item: @ast::foreign_item, tys: @c_stack_tys,
                       cc: lib::llvm::CallConv) {
        let fcx = new_fn_ctxt(ccx, ~[], decl, None);
        let bcx = top_scope_block(fcx, None), lltop = bcx.llbb;
        let llbasefn = base_fn(ccx, link_name(ccx, item), tys, cc);
        let ty = ty::lookup_item_type(ccx.tcx,
                                      ast_util::local_def(item.id)).ty;
        let args = vec::from_fn(ty::ty_fn_args(ty).len(), |i| {
            get_param(decl, i + first_real_arg)
        });
        let retval = Call(bcx, llbasefn, args);
        if !ty::type_is_nil(ty::ty_fn_ret(ty)) {
            Store(bcx, retval, fcx.llretptr);
        }
        build_return(bcx);
        finish_fn(fcx, lltop);
    }

    fn build_wrap_fn(ccx: @crate_ctxt,
                     tys: @c_stack_tys,
                     llshimfn: ValueRef,
                     llwrapfn: ValueRef) {

        let _icx = ccx.insn_ctxt("foreign::build_wrap_fn");

        fn build_args(bcx: block, tys: @c_stack_tys,
                      llwrapfn: ValueRef, llargbundle: ValueRef) {
            let _icx = bcx.insn_ctxt("foreign::wrap::build_args");
            let mut i = 0u;
            let n = vec::len(tys.arg_tys);
            let implicit_args = first_real_arg; // return + env
            while i < n {
                let llargval = get_param(llwrapfn, i + implicit_args);
                store_inbounds(bcx, llargval, llargbundle, ~[0u, i]);
                i += 1u;
            }
            let llretptr = get_param(llwrapfn, 0u);
            store_inbounds(bcx, llretptr, llargbundle, ~[0u, n]);
        }

        fn build_ret(bcx: block, _tys: @c_stack_tys,
                     _llargbundle: ValueRef) {
            let _icx = bcx.insn_ctxt("foreign::wrap::build_ret");
            RetVoid(bcx);
        }

        build_wrap_fn_(ccx, tys, llshimfn, llwrapfn,
                       ccx.upcalls.call_shim_on_c_stack,
                       build_args, build_ret);
    }

    let mut cc = match abi {
      ast::foreign_abi_rust_intrinsic |
      ast::foreign_abi_cdecl => lib::llvm::CCallConv,
      ast::foreign_abi_stdcall => lib::llvm::X86StdcallCallConv
    };

    for vec::each(foreign_mod.items) |foreign_item| {
      match foreign_item.node {
        ast::foreign_item_fn(*) => {
          let id = foreign_item.id;
          if abi != ast::foreign_abi_rust_intrinsic {
              let llwrapfn = get_item_val(ccx, id);
              let tys = c_stack_tys(ccx, id);
              if attr::attrs_contains_name(foreign_item.attrs, "rust_stack") {
                  build_direct_fn(ccx, llwrapfn, *foreign_item, tys, cc);
              } else {
                  let llshimfn = build_shim_fn(ccx, *foreign_item, tys, cc);
                  build_wrap_fn(ccx, tys, llshimfn, llwrapfn);
              }
          } else {
              // Intrinsics are emitted by monomorphic fn
          }
        }
        ast::foreign_item_const(*) => {
            let ident = ccx.sess.parse_sess.interner.get(foreign_item.ident);
            ccx.item_symbols.insert(foreign_item.id, copy *ident);
        }
      }
    }
}

fn trans_intrinsic(ccx: @crate_ctxt, decl: ValueRef, item: @ast::foreign_item,
                   +path: ast_map::path, +substs: param_substs,
                   ref_id: Option<ast::node_id>)
{
    debug!("trans_intrinsic(item.ident=%s)", ccx.sess.str_of(item.ident));

    // XXX: Bad copy.
    let fcx = new_fn_ctxt_w_id(ccx, path, decl, item.id, None,
                               Some(copy substs), Some(item.span));
    let mut bcx = top_scope_block(fcx, None), lltop = bcx.llbb;
    match ccx.sess.str_of(item.ident) {
        ~"atomic_cxchg" => {
            let old = AtomicCmpXchg(bcx,
                                    get_param(decl, first_real_arg),
                                    get_param(decl, first_real_arg + 1u),
                                    get_param(decl, first_real_arg + 2u),
                                    SequentiallyConsistent);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_cxchg_acq" => {
            let old = AtomicCmpXchg(bcx,
                                    get_param(decl, first_real_arg),
                                    get_param(decl, first_real_arg + 1u),
                                    get_param(decl, first_real_arg + 2u),
                                    Acquire);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_cxchg_rel" => {
            let old = AtomicCmpXchg(bcx,
                                    get_param(decl, first_real_arg),
                                    get_param(decl, first_real_arg + 1u),
                                    get_param(decl, first_real_arg + 2u),
                                    Release);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xchg" => {
            let old = AtomicRMW(bcx, Xchg,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                SequentiallyConsistent);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xchg_acq" => {
            let old = AtomicRMW(bcx, Xchg,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Acquire);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xchg_rel" => {
            let old = AtomicRMW(bcx, Xchg,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Release);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xadd" => {
            let old = AtomicRMW(bcx, lib::llvm::Add,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                SequentiallyConsistent);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xadd_acq" => {
            let old = AtomicRMW(bcx, lib::llvm::Add,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Acquire);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xadd_rel" => {
            let old = AtomicRMW(bcx, lib::llvm::Add,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Release);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xsub" => {
            let old = AtomicRMW(bcx, lib::llvm::Sub,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                SequentiallyConsistent);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xsub_acq" => {
            let old = AtomicRMW(bcx, lib::llvm::Sub,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Acquire);
            Store(bcx, old, fcx.llretptr);
        }
        ~"atomic_xsub_rel" => {
            let old = AtomicRMW(bcx, lib::llvm::Sub,
                                get_param(decl, first_real_arg),
                                get_param(decl, first_real_arg + 1u),
                                Release);
            Store(bcx, old, fcx.llretptr);
        }
        ~"size_of" => {
            let tp_ty = substs.tys[0];
            let lltp_ty = type_of::type_of(ccx, tp_ty);
            Store(bcx, C_uint(ccx, shape::llsize_of_real(ccx, lltp_ty)),
                  fcx.llretptr);
        }
        ~"move_val" => {
            // Create a datum reflecting the value being moved:
            //
            // - the datum will be by ref if the value is non-immediate;
            //
            // - the datum has a FromRvalue source because, that way,
            //   the `move_to()` method does not feel compelled to
            //   zero out the memory where the datum resides.  Zeroing
            //   is not necessary since, for intrinsics, there is no
            //   cleanup to concern ourselves with.
            let tp_ty = substs.tys[0];
            let mode = appropriate_mode(tp_ty);
            let src = Datum {val: get_param(decl, first_real_arg + 1u),
                             ty: tp_ty, mode: mode, source: FromRvalue};
            bcx = src.move_to(bcx, DROP_EXISTING,
                              get_param(decl, first_real_arg));
        }
        ~"move_val_init" => {
            // See comments for `"move_val"`.
            let tp_ty = substs.tys[0];
            let mode = appropriate_mode(tp_ty);
            let src = Datum {val: get_param(decl, first_real_arg + 1u),
                             ty: tp_ty, mode: mode, source: FromRvalue};
            bcx = src.move_to(bcx, INIT, get_param(decl, first_real_arg));
        }
        ~"min_align_of" => {
            let tp_ty = substs.tys[0];
            let lltp_ty = type_of::type_of(ccx, tp_ty);
            Store(bcx, C_uint(ccx, shape::llalign_of_min(ccx, lltp_ty)),
                  fcx.llretptr);
        }
        ~"pref_align_of"=> {
            let tp_ty = substs.tys[0];
            let lltp_ty = type_of::type_of(ccx, tp_ty);
            Store(bcx, C_uint(ccx, shape::llalign_of_pref(ccx, lltp_ty)),
                  fcx.llretptr);
        }
        ~"get_tydesc" => {
            let tp_ty = substs.tys[0];
            let static_ti = get_tydesc(ccx, tp_ty);
            glue::lazily_emit_all_tydesc_glue(ccx, static_ti);

            // FIXME (#3727): change this to T_ptr(ccx.tydesc_ty) when the
            // core::sys copy of the get_tydesc interface dies off.
            let td = PointerCast(bcx, static_ti.tydesc, T_ptr(T_nil()));
            Store(bcx, td, fcx.llretptr);
        }
        ~"init" => {
            let tp_ty = substs.tys[0];
            let lltp_ty = type_of::type_of(ccx, tp_ty);
            if !ty::type_is_nil(tp_ty) {
                Store(bcx, C_null(lltp_ty), fcx.llretptr);
            }
        }
        ~"forget" => {}
        ~"reinterpret_cast" => {
            let tp_ty = substs.tys[0];
            let lltp_ty = type_of::type_of(ccx, tp_ty);
            let llout_ty = type_of::type_of(ccx, substs.tys[1]);
            let tp_sz = machine::llbitsize_of_real(ccx, lltp_ty),
            out_sz = machine::llbitsize_of_real(ccx, llout_ty);
          if tp_sz != out_sz {
              let sp = match ccx.tcx.items.get(ref_id.get()) {
                  ast_map::node_expr(e) => e.span,
                  _ => fail ~"reinterpret_cast or forget has non-expr arg"
              };
              ccx.sess.span_fatal(
                  sp, fmt!("reinterpret_cast called on types \
                            with different size: %s (%u bit(s)) to %s \
                            (%u bit(s))",
                           ty_to_str(ccx.tcx, tp_ty), tp_sz,
                           ty_to_str(ccx.tcx, substs.tys[1]), out_sz));
          }
          if !ty::type_is_nil(substs.tys[1]) {
              // NB: Do not use a Load and Store here. This causes
              // massive code bloat when reinterpret_cast is used on
              // large structural types.
              let llretptr = PointerCast(bcx, fcx.llretptr, T_ptr(T_i8()));
              let llcast = get_param(decl, first_real_arg);
              let llcast = PointerCast(bcx, llcast, T_ptr(T_i8()));
              call_memcpy(bcx, llretptr, llcast, llsize_of(ccx, lltp_ty));
          }
        }
        ~"addr_of" => {
            Store(bcx, get_param(decl, first_real_arg), fcx.llretptr);
        }
        ~"needs_drop" => {
            let tp_ty = substs.tys[0];
            Store(bcx, C_bool(ty::type_needs_drop(ccx.tcx, tp_ty)),
                  fcx.llretptr);
        }
        ~"visit_tydesc" => {
            let td = get_param(decl, first_real_arg);
            let visitor = get_param(decl, first_real_arg + 1u);
            let td = PointerCast(bcx, td, T_ptr(ccx.tydesc_type));
            glue::call_tydesc_glue_full(bcx, visitor, td,
                                        abi::tydesc_field_visit_glue, None);
        }
        ~"frame_address" => {
            let frameaddress = ccx.intrinsics.get(~"llvm.frameaddress");
            let frameaddress_val = Call(bcx, frameaddress, ~[C_i32(0i32)]);
            let star_u8 = ty::mk_imm_ptr(
                bcx.tcx(),
                ty::mk_mach_uint(bcx.tcx(), ast::ty_u8));
            let fty = ty::mk_fn(bcx.tcx(), FnTyBase {
                meta: FnMeta {purity: ast::impure_fn,
                              proto: ast::ProtoBorrowed,
                              onceness: ast::Many,
                              region: ty::re_bound(ty::br_anon(0)),
                              bounds: @~[]},
                sig: FnSig {inputs: ~[arg {mode: ast::expl(ast::by_val),
                                           ty: star_u8}],
                            output: ty::mk_nil(bcx.tcx())}
            });
            let datum = Datum {val: get_param(decl, first_real_arg),
                               mode: ByRef, ty: fty, source: FromLvalue};
            bcx = trans_call_inner(
                bcx, None, fty, ty::mk_nil(bcx.tcx()),
                |bcx| Callee {bcx: bcx, data: Closure(datum)},
                ArgVals(~[frameaddress_val]), Ignore, DontAutorefArg);
        }
        ~"morestack_addr" => {
            // XXX This is a hack to grab the address of this particular
            // native function. There should be a general in-language
            // way to do this
            let llfty = type_of_fn(bcx.ccx(), ~[], ty::mk_nil(bcx.tcx()));
            let morestack_addr = decl_cdecl_fn(
                bcx.ccx().llmod, ~"__morestack", llfty);
            let morestack_addr = PointerCast(bcx, morestack_addr,
                                             T_ptr(T_nil()));
            Store(bcx, morestack_addr, fcx.llretptr);
        }
        ~"memmove32" => {
            let dst_ptr = get_param(decl, first_real_arg);
            let src_ptr = get_param(decl, first_real_arg + 1);
            let size = get_param(decl, first_real_arg + 2);
            let align = C_i32(1);
            let volatile = C_bool(false);
            let llfn = bcx.ccx().intrinsics.get(
                ~"llvm.memmove.p0i8.p0i8.i32");
            Call(bcx, llfn, ~[dst_ptr, src_ptr, size, align, volatile]);
        }
        ~"memmove64" => {
            let dst_ptr = get_param(decl, first_real_arg);
            let src_ptr = get_param(decl, first_real_arg + 1);
            let size = get_param(decl, first_real_arg + 2);
            let align = C_i32(1);
            let volatile = C_bool(false);
            let llfn = bcx.ccx().intrinsics.get(
                ~"llvm.memmove.p0i8.p0i8.i64");
            Call(bcx, llfn, ~[dst_ptr, src_ptr, size, align, volatile]);
        }
        ~"sqrtf32" => {
            let x = get_param(decl, first_real_arg);
            let sqrtf = ccx.intrinsics.get(~"llvm.sqrt.f32");
            Store(bcx, Call(bcx, sqrtf, ~[x]), fcx.llretptr);
        }
        ~"sqrtf64" => {
            let x = get_param(decl, first_real_arg);
            let sqrtf = ccx.intrinsics.get(~"llvm.sqrt.f64");
            Store(bcx, Call(bcx, sqrtf, ~[x]), fcx.llretptr);
        }
        ~"powif32" => {
            let a = get_param(decl, first_real_arg);
            let x = get_param(decl, first_real_arg + 1u);
            let powif = ccx.intrinsics.get(~"llvm.powi.f32");
            Store(bcx, Call(bcx, powif, ~[a, x]), fcx.llretptr);
        }
        ~"powif64" => {
            let a = get_param(decl, first_real_arg);
            let x = get_param(decl, first_real_arg + 1u);
            let powif = ccx.intrinsics.get(~"llvm.powi.f64");
            Store(bcx, Call(bcx, powif, ~[a, x]), fcx.llretptr);
        }
        ~"sinf32" => {
            let x = get_param(decl, first_real_arg);
            let sinf = ccx.intrinsics.get(~"llvm.sin.f32");
            Store(bcx, Call(bcx, sinf, ~[x]), fcx.llretptr);
        }
        ~"sinf64" => {
            let x = get_param(decl, first_real_arg);
            let sinf = ccx.intrinsics.get(~"llvm.sin.f64");
            Store(bcx, Call(bcx, sinf, ~[x]), fcx.llretptr);
        }
        ~"cosf32" => {
            let x = get_param(decl, first_real_arg);
            let cosf = ccx.intrinsics.get(~"llvm.cos.f32");
            Store(bcx, Call(bcx, cosf, ~[x]), fcx.llretptr);
        }
        ~"cosf64" => {
            let x = get_param(decl, first_real_arg);
            let cosf = ccx.intrinsics.get(~"llvm.cos.f64");
            Store(bcx, Call(bcx, cosf, ~[x]), fcx.llretptr);
        }
        ~"powf32" => {
            let a = get_param(decl, first_real_arg);
            let x = get_param(decl, first_real_arg + 1u);
            let powf = ccx.intrinsics.get(~"llvm.pow.f32");
            Store(bcx, Call(bcx, powf, ~[a, x]), fcx.llretptr);
        }
        ~"powf64" => {
            let a = get_param(decl, first_real_arg);
            let x = get_param(decl, first_real_arg + 1u);
            let powf = ccx.intrinsics.get(~"llvm.pow.f64");
            Store(bcx, Call(bcx, powf, ~[a, x]), fcx.llretptr);
        }
        ~"expf32" => {
            let x = get_param(decl, first_real_arg);
            let expf = ccx.intrinsics.get(~"llvm.exp.f32");
            Store(bcx, Call(bcx, expf, ~[x]), fcx.llretptr);
        }
        ~"expf64" => {
            let x = get_param(decl, first_real_arg);
            let expf = ccx.intrinsics.get(~"llvm.exp.f64");
            Store(bcx, Call(bcx, expf, ~[x]), fcx.llretptr);
        }
        ~"exp2f32" => {
            let x = get_param(decl, first_real_arg);
            let exp2f = ccx.intrinsics.get(~"llvm.exp2.f32");
            Store(bcx, Call(bcx, exp2f, ~[x]), fcx.llretptr);
        }
        ~"exp2f64" => {
            let x = get_param(decl, first_real_arg);
            let exp2f = ccx.intrinsics.get(~"llvm.exp2.f64");
            Store(bcx, Call(bcx, exp2f, ~[x]), fcx.llretptr);
        }
        ~"logf32" => {
            let x = get_param(decl, first_real_arg);
            let logf = ccx.intrinsics.get(~"llvm.log.f32");
            Store(bcx, Call(bcx, logf, ~[x]), fcx.llretptr);
        }
        ~"logf64" => {
            let x = get_param(decl, first_real_arg);
            let logf = ccx.intrinsics.get(~"llvm.log.f64");
            Store(bcx, Call(bcx, logf, ~[x]), fcx.llretptr);
        }
        ~"log10f32" => {
            let x = get_param(decl, first_real_arg);
            let log10f = ccx.intrinsics.get(~"llvm.log10.f32");
            Store(bcx, Call(bcx, log10f, ~[x]), fcx.llretptr);
        }
        ~"log10f64" => {
            let x = get_param(decl, first_real_arg);
            let log10f = ccx.intrinsics.get(~"llvm.log10.f64");
            Store(bcx, Call(bcx, log10f, ~[x]), fcx.llretptr);
        }
        ~"log2f32" => {
            let x = get_param(decl, first_real_arg);
            let log2f = ccx.intrinsics.get(~"llvm.log2.f32");
            Store(bcx, Call(bcx, log2f, ~[x]), fcx.llretptr);
        }
        ~"log2f64" => {
            let x = get_param(decl, first_real_arg);
            let log2f = ccx.intrinsics.get(~"llvm.log2.f64");
            Store(bcx, Call(bcx, log2f, ~[x]), fcx.llretptr);
        }
        ~"fmaf32" => {
            let a = get_param(decl, first_real_arg);
            let b = get_param(decl, first_real_arg + 1u);
            let c = get_param(decl, first_real_arg + 2u);
            let fmaf = ccx.intrinsics.get(~"llvm.fma.f32");
            Store(bcx, Call(bcx, fmaf, ~[a, b, c]), fcx.llretptr);
        }
        ~"fmaf64" => {
            let a = get_param(decl, first_real_arg);
            let b = get_param(decl, first_real_arg + 1u);
            let c = get_param(decl, first_real_arg + 2u);
            let fmaf = ccx.intrinsics.get(~"llvm.fma.f64");
            Store(bcx, Call(bcx, fmaf, ~[a, b, c]), fcx.llretptr);
        }
        ~"fabsf32" => {
            let x = get_param(decl, first_real_arg);
            let fabsf = ccx.intrinsics.get(~"llvm.fabs.f32");
            Store(bcx, Call(bcx, fabsf, ~[x]), fcx.llretptr);
        }
        ~"fabsf64" => {
            let x = get_param(decl, first_real_arg);
            let fabsf = ccx.intrinsics.get(~"llvm.fabs.f64");
            Store(bcx, Call(bcx, fabsf, ~[x]), fcx.llretptr);
        }
        ~"floorf32" => {
            let x = get_param(decl, first_real_arg);
            let floorf = ccx.intrinsics.get(~"llvm.floor.f32");
            Store(bcx, Call(bcx, floorf, ~[x]), fcx.llretptr);
        }
        ~"floorf64" => {
            let x = get_param(decl, first_real_arg);
            let floorf = ccx.intrinsics.get(~"llvm.floor.f64");
            Store(bcx, Call(bcx, floorf, ~[x]), fcx.llretptr);
        }
        ~"ceilf32" => {
            let x = get_param(decl, first_real_arg);
            let ceilf = ccx.intrinsics.get(~"llvm.ceil.f32");
            Store(bcx, Call(bcx, ceilf, ~[x]), fcx.llretptr);
        }
        ~"ceilf64" => {
            let x = get_param(decl, first_real_arg);
            let ceilf = ccx.intrinsics.get(~"llvm.ceil.f64");
            Store(bcx, Call(bcx, ceilf, ~[x]), fcx.llretptr);
        }
        ~"truncf32" => {
            let x = get_param(decl, first_real_arg);
            let truncf = ccx.intrinsics.get(~"llvm.trunc.f32");
            Store(bcx, Call(bcx, truncf, ~[x]), fcx.llretptr);
        }
        ~"truncf64" => {
            let x = get_param(decl, first_real_arg);
            let truncf = ccx.intrinsics.get(~"llvm.trunc.f64");
            Store(bcx, Call(bcx, truncf, ~[x]), fcx.llretptr);
        }
        ~"ctpop8" => {
            let x = get_param(decl, first_real_arg);
            let ctpop = ccx.intrinsics.get(~"llvm.ctpop.i8");
            Store(bcx, Call(bcx, ctpop, ~[x]), fcx.llretptr)
        }
        ~"ctpop16" => {
            let x = get_param(decl, first_real_arg);
            let ctpop = ccx.intrinsics.get(~"llvm.ctpop.i16");
            Store(bcx, Call(bcx, ctpop, ~[x]), fcx.llretptr)
        }
        ~"ctpop32" => {
            let x = get_param(decl, first_real_arg);
            let ctpop = ccx.intrinsics.get(~"llvm.ctpop.i32");
            Store(bcx, Call(bcx, ctpop, ~[x]), fcx.llretptr)
        }
        ~"ctpop64" => {
            let x = get_param(decl, first_real_arg);
            let ctpop = ccx.intrinsics.get(~"llvm.ctpop.i64");
            Store(bcx, Call(bcx, ctpop, ~[x]), fcx.llretptr)
        }
        ~"ctlz8" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let ctlz = ccx.intrinsics.get(~"llvm.ctlz.i8");
            Store(bcx, Call(bcx, ctlz, ~[x, y]), fcx.llretptr)
        }
        ~"ctlz16" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let ctlz = ccx.intrinsics.get(~"llvm.ctlz.i16");
            Store(bcx, Call(bcx, ctlz, ~[x, y]), fcx.llretptr)
        }
        ~"ctlz32" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let ctlz = ccx.intrinsics.get(~"llvm.ctlz.i32");
            Store(bcx, Call(bcx, ctlz, ~[x, y]), fcx.llretptr)
        }
        ~"ctlz64" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let ctlz = ccx.intrinsics.get(~"llvm.ctlz.i64");
            Store(bcx, Call(bcx, ctlz, ~[x, y]), fcx.llretptr)
        }
        ~"cttz8" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let cttz = ccx.intrinsics.get(~"llvm.cttz.i8");
            Store(bcx, Call(bcx, cttz, ~[x, y]), fcx.llretptr)
        }
        ~"cttz16" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let cttz = ccx.intrinsics.get(~"llvm.cttz.i16");
            Store(bcx, Call(bcx, cttz, ~[x, y]), fcx.llretptr)
        }
        ~"cttz32" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let cttz = ccx.intrinsics.get(~"llvm.cttz.i32");
            Store(bcx, Call(bcx, cttz, ~[x, y]), fcx.llretptr)
        }
        ~"cttz64" => {
            let x = get_param(decl, first_real_arg);
            let y = C_bool(false);
            let cttz = ccx.intrinsics.get(~"llvm.cttz.i64");
            Store(bcx, Call(bcx, cttz, ~[x, y]), fcx.llretptr)
        }
        ~"bswap16" => {
            let x = get_param(decl, first_real_arg);
            let cttz = ccx.intrinsics.get(~"llvm.bswap.i16");
            Store(bcx, Call(bcx, cttz, ~[x]), fcx.llretptr)
        }
        ~"bswap32" => {
            let x = get_param(decl, first_real_arg);
            let cttz = ccx.intrinsics.get(~"llvm.bswap.i32");
            Store(bcx, Call(bcx, cttz, ~[x]), fcx.llretptr)
        }
        ~"bswap64" => {
            let x = get_param(decl, first_real_arg);
            let cttz = ccx.intrinsics.get(~"llvm.bswap.i64");
            Store(bcx, Call(bcx, cttz, ~[x]), fcx.llretptr)
        }
        _ => {
            // Could we make this an enum rather than a string? does it get
            // checked earlier?
            ccx.sess.span_bug(item.span, ~"unknown intrinsic");
        }
    }
    build_return(bcx);
    finish_fn(fcx, lltop);
}

fn trans_foreign_fn(ccx: @crate_ctxt, +path: ast_map::path,
                    decl: ast::fn_decl, body: ast::blk, llwrapfn: ValueRef,
                    id: ast::node_id) {
    let _icx = ccx.insn_ctxt("foreign::build_foreign_fn");

    fn build_rust_fn(ccx: @crate_ctxt, +path: ast_map::path,
                     decl: ast::fn_decl, body: ast::blk,
                     id: ast::node_id) -> ValueRef {
        let _icx = ccx.insn_ctxt("foreign::foreign::build_rust_fn");
        let t = ty::node_id_to_type(ccx.tcx, id);
        // XXX: Bad copy.
        let ps = link::mangle_internal_name_by_path(
            ccx, vec::append_one(copy path, ast_map::path_name(
                special_idents::clownshoe_abi
            )));
        let llty = type_of_fn_from_ty(ccx, t);
        let llfndecl = decl_internal_cdecl_fn(ccx.llmod, ps, llty);
        trans_fn(ccx, path, decl, body, llfndecl, no_self, None, id, None);
        return llfndecl;
    }

    fn build_shim_fn(ccx: @crate_ctxt, +path: ast_map::path,
                     llrustfn: ValueRef, tys: @c_stack_tys) -> ValueRef {
        let _icx = ccx.insn_ctxt("foreign::foreign::build_shim_fn");

        fn build_args(bcx: block, tys: @c_stack_tys,
                      llargbundle: ValueRef) -> ~[ValueRef] {
            let _icx = bcx.insn_ctxt("foreign::extern::shim::build_args");
            let mut llargvals = ~[];
            let mut i = 0u;
            let n = vec::len(tys.arg_tys);
            let llretptr = load_inbounds(bcx, llargbundle, ~[0u, n]);
            llargvals.push(llretptr);
            let llenvptr = C_null(T_opaque_box_ptr(bcx.ccx()));
            llargvals.push(llenvptr);
            while i < n {
                let llargval = load_inbounds(bcx, llargbundle, ~[0u, i]);
                llargvals.push(llargval);
                i += 1u;
            }
            return llargvals;
        }

        fn build_ret(_bcx: block, _tys: @c_stack_tys,
                     _llargbundle: ValueRef, _llretval: ValueRef)  {
            // Nop. The return pointer in the Rust ABI function
            // is wired directly into the return slot in the shim struct
        }

        let shim_name = link::mangle_internal_name_by_path(
            ccx, vec::append_one(path, ast_map::path_name(
                special_idents::clownshoe_stack_shim
            )));
        return build_shim_fn_(ccx, shim_name, llrustfn, tys,
                           lib::llvm::CCallConv,
                           build_args, build_ret);
    }

    fn build_wrap_fn(ccx: @crate_ctxt, llshimfn: ValueRef,
                     llwrapfn: ValueRef, tys: @c_stack_tys) {

        let _icx = ccx.insn_ctxt("foreign::foreign::build_wrap_fn");

        fn build_args(bcx: block, tys: @c_stack_tys,
                      llwrapfn: ValueRef, llargbundle: ValueRef) {
            let _icx = bcx.insn_ctxt("foreign::foreign::wrap::build_args");
            tys.fn_ty.build_wrap_args(bcx, tys.ret_ty,
                                      llwrapfn, llargbundle);
        }

        fn build_ret(bcx: block, tys: @c_stack_tys,
                     llargbundle: ValueRef) {
            let _icx = bcx.insn_ctxt("foreign::foreign::wrap::build_ret");
            tys.fn_ty.build_wrap_ret(bcx, tys.arg_tys, llargbundle);
        }

        build_wrap_fn_(ccx, tys, llshimfn, llwrapfn,
                       ccx.upcalls.call_shim_on_rust_stack,
                       build_args, build_ret);
    }

    let tys = c_stack_tys(ccx, id);
    // The internal Rust ABI function - runs on the Rust stack
    // XXX: Bad copy.
    let llrustfn = build_rust_fn(ccx, copy path, decl, body, id);
    // The internal shim function - runs on the Rust stack
    let llshimfn = build_shim_fn(ccx, path, llrustfn, tys);
    // The foreign C function - runs on the C stack
    build_wrap_fn(ccx, llshimfn, llwrapfn, tys)
}

fn register_foreign_fn(ccx: @crate_ctxt,
                       sp: span,
                       +path: ast_map::path,
                       node_id: ast::node_id,
                       attrs: &[ast::attribute])
                    -> ValueRef {
    let _icx = ccx.insn_ctxt("foreign::register_foreign_fn");
    let t = ty::node_id_to_type(ccx.tcx, node_id);
    let (llargtys, llretty, ret_ty) = c_arg_and_ret_lltys(ccx, node_id);
    let ret_def = !ty::type_is_bot(ret_ty) && !ty::type_is_nil(ret_ty);
    let fn_ty = abi_info(ccx.sess.targ_cfg.arch).
                    compute_info(llargtys, llretty, ret_def);
    do fn_ty.decl_fn |fnty| {
        register_fn_fuller(ccx, sp, /*bad*/copy path, node_id, attrs,
                           t, lib::llvm::CCallConv, fnty)
    }
}

fn abi_of_foreign_fn(ccx: @crate_ctxt, i: @ast::foreign_item)
    -> ast::foreign_abi {
    match attr::first_attr_value_str_by_name(i.attrs, ~"abi") {
      None => match ccx.tcx.items.get(i.id) {
        ast_map::node_foreign_item(_, abi, _) => abi,
        // ??
        _ => fail ~"abi_of_foreign_fn: not foreign"
      },
      Some(_) => match attr::foreign_abi(i.attrs) {
        either::Right(abi) => abi,
        either::Left(ref msg) => {
            ccx.sess.span_fatal(i.span, (/*bad*/copy *msg))
        }
      }
    }
}