// 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. /*! * Handles translation of callees as well as other call-related * things. Callees are a superset of normal rust values and sometimes * have different representations. In particular, top-level fn items * and methods are represented as just a fn ptr and not a full * closure. */ use std::vec; use back::abi; use driver::session; use lib::llvm::{ValueRef, NoAliasAttribute, StructRetAttribute}; use lib::llvm::llvm; use metadata::csearch; use middle::trans::base; use middle::trans::base::*; use middle::trans::build::*; use middle::trans::callee; use middle::trans::cleanup; use middle::trans::cleanup::CleanupMethods; use middle::trans::common; use middle::trans::common::*; use middle::trans::datum::*; use middle::trans::datum::Datum; use middle::trans::expr; use middle::trans::glue; use middle::trans::inline; use middle::trans::meth; use middle::trans::monomorphize; use middle::trans::type_of; use middle::trans::foreign; use middle::ty; use middle::subst::Subst; use middle::typeck; use middle::typeck::coherence::make_substs_for_receiver_types; use middle::typeck::MethodCall; use util::ppaux::Repr; use middle::trans::type_::Type; use std::vec_ng::Vec; use std::vec_ng; use syntax::ast; use syntax::abi::AbiSet; use syntax::ast_map; pub struct MethodData { llfn: ValueRef, llself: ValueRef, } pub enum CalleeData { Closure(Datum), // Represents a (possibly monomorphized) top-level fn item or method // item. Note that this is just the fn-ptr and is not a Rust closure // value (which is a pair). Fn(/* llfn */ ValueRef), TraitMethod(MethodData) } pub struct Callee<'a> { bcx: &'a Block<'a>, data: CalleeData } fn trans<'a>(bcx: &'a Block<'a>, expr: &ast::Expr) -> Callee<'a> { let _icx = push_ctxt("trans_callee"); debug!("callee::trans(expr={})", expr.repr(bcx.tcx())); // pick out special kinds of expressions that can be called: match expr.node { ast::ExprPath(_) => { return trans_def(bcx, bcx.def(expr.id), expr); } _ => {} } // any other expressions are closures: return datum_callee(bcx, expr); fn datum_callee<'a>(bcx: &'a Block<'a>, expr: &ast::Expr) -> Callee<'a> { let DatumBlock {bcx: mut bcx, datum} = expr::trans(bcx, expr); match ty::get(datum.ty).sty { ty::ty_bare_fn(..) => { let llval = datum.to_llscalarish(bcx); return Callee {bcx: bcx, data: Fn(llval)}; } ty::ty_closure(..) => { let datum = unpack_datum!( bcx, datum.to_lvalue_datum(bcx, "callee", expr.id)); return Callee {bcx: bcx, data: Closure(datum)}; } _ => { bcx.tcx().sess.span_bug( expr.span, format!("type of callee is neither bare-fn nor closure: {}", bcx.ty_to_str(datum.ty))); } } } fn fn_callee<'a>(bcx: &'a Block<'a>, llfn: ValueRef) -> Callee<'a> { return Callee {bcx: bcx, data: Fn(llfn)}; } fn trans_def<'a>(bcx: &'a Block<'a>, def: ast::Def, ref_expr: &ast::Expr) -> Callee<'a> { match def { ast::DefFn(did, _) | ast::DefStaticMethod(did, ast::FromImpl(_), _) => { fn_callee(bcx, trans_fn_ref(bcx, did, ExprId(ref_expr.id))) } ast::DefStaticMethod(impl_did, ast::FromTrait(trait_did), _) => { fn_callee(bcx, meth::trans_static_method_callee(bcx, impl_did, trait_did, ref_expr.id)) } ast::DefVariant(tid, vid, _) => { // nullary variants are not callable assert!(ty::enum_variant_with_id(bcx.tcx(), tid, vid).args.len() > 0u); fn_callee(bcx, trans_fn_ref(bcx, vid, ExprId(ref_expr.id))) } ast::DefStruct(def_id) => { fn_callee(bcx, trans_fn_ref(bcx, def_id, ExprId(ref_expr.id))) } ast::DefStatic(..) | ast::DefArg(..) | ast::DefLocal(..) | ast::DefBinding(..) | ast::DefUpvar(..) => { datum_callee(bcx, ref_expr) } ast::DefMod(..) | ast::DefForeignMod(..) | ast::DefTrait(..) | ast::DefTy(..) | ast::DefPrimTy(..) | ast::DefUse(..) | ast::DefTyParamBinder(..) | ast::DefRegion(..) | ast::DefLabel(..) | ast::DefTyParam(..) | ast::DefSelfTy(..) | ast::DefMethod(..) => { bcx.tcx().sess.span_bug( ref_expr.span, format!("cannot translate def {:?} \ to a callable thing!", def)); } } } } pub fn trans_fn_ref(bcx: &Block, def_id: ast::DefId, node: ExprOrMethodCall) -> ValueRef { /*! * * Translates a reference (with id `ref_id`) to the fn/method * with id `def_id` into a function pointer. This may require * monomorphization or inlining. */ let _icx = push_ctxt("trans_fn_ref"); let type_params = node_id_type_params(bcx, node); let vtables = match node { ExprId(id) => node_vtables(bcx, id), MethodCall(method_call) if method_call.autoderef == 0 => { node_vtables(bcx, method_call.expr_id) } _ => None }; debug!("trans_fn_ref(def_id={}, node={:?}, type_params={}, vtables={})", def_id.repr(bcx.tcx()), node, type_params.repr(bcx.tcx()), vtables.repr(bcx.tcx())); trans_fn_ref_with_vtables(bcx, def_id, node, type_params.as_slice(), vtables) } fn trans_fn_ref_with_vtables_to_callee<'a>(bcx: &'a Block<'a>, def_id: ast::DefId, ref_id: ast::NodeId, type_params: &[ty::t], vtables: Option) -> Callee<'a> { Callee {bcx: bcx, data: Fn(trans_fn_ref_with_vtables(bcx, def_id, ExprId(ref_id), type_params, vtables))} } fn resolve_default_method_vtables(bcx: &Block, impl_id: ast::DefId, method: &ty::Method, substs: &ty::substs, impl_vtables: Option) -> (typeck::vtable_res, typeck::vtable_param_res) { // Get the vtables that the impl implements the trait at let impl_res = ty::lookup_impl_vtables(bcx.tcx(), impl_id); // Build up a param_substs that we are going to resolve the // trait_vtables under. let param_substs = Some(@param_substs { tys: substs.tps.clone(), self_ty: substs.self_ty, vtables: impl_vtables, self_vtables: None }); let trait_vtables_fixed = resolve_vtables_under_param_substs( bcx.tcx(), param_substs, impl_res.trait_vtables); // Now we pull any vtables for parameters on the actual method. let num_method_vtables = method.generics.type_param_defs().len(); let method_vtables = match impl_vtables { Some(vtables) => { let num_impl_type_parameters = vtables.len() - num_method_vtables; vtables.tailn(num_impl_type_parameters).to_owned() }, None => vec::from_elem(num_method_vtables, @Vec::new()) }; let param_vtables = @(vec_ng::append((*trait_vtables_fixed).clone(), method_vtables)); let self_vtables = resolve_param_vtables_under_param_substs( bcx.tcx(), param_substs, impl_res.self_vtables); (param_vtables, self_vtables) } pub fn trans_fn_ref_with_vtables( bcx: &Block, // def_id: ast::DefId, // def id of fn node: ExprOrMethodCall, // node id of use of fn; may be zero if N/A type_params: &[ty::t], // values for fn's ty params vtables: Option) // vtables for the call -> ValueRef { /*! * Translates a reference to a fn/method item, monomorphizing and * inlining as it goes. * * # Parameters * * - `bcx`: the current block where the reference to the fn occurs * - `def_id`: def id of the fn or method item being referenced * - `node`: node id of the reference to the fn/method, if applicable. * This parameter may be zero; but, if so, the resulting value may not * have the right type, so it must be cast before being used. * - `type_params`: values for each of the fn/method's type parameters * - `vtables`: values for each bound on each of the type parameters */ let _icx = push_ctxt("trans_fn_ref_with_vtables"); let ccx = bcx.ccx(); let tcx = ccx.tcx; debug!("trans_fn_ref_with_vtables(bcx={}, def_id={}, node={:?}, \ type_params={}, vtables={})", bcx.to_str(), def_id.repr(bcx.tcx()), node, type_params.repr(bcx.tcx()), vtables.repr(bcx.tcx())); assert!(type_params.iter().all(|t| !ty::type_needs_infer(*t))); // Polytype of the function item (may have type params) let fn_tpt = ty::lookup_item_type(tcx, def_id); let substs = ty::substs { regions: ty::ErasedRegions, self_ty: None, tps: /*bad*/ Vec::from_slice(type_params) }; // Load the info for the appropriate trait if necessary. match ty::trait_of_method(tcx, def_id) { None => {} Some(trait_id) => { ty::populate_implementations_for_trait_if_necessary(tcx, trait_id) } } // We need to do a bunch of special handling for default methods. // We need to modify the def_id and our substs in order to monomorphize // the function. let (is_default, def_id, substs, self_vtables, vtables) = match ty::provided_source(tcx, def_id) { None => (false, def_id, substs, None, vtables), Some(source_id) => { // There are two relevant substitutions when compiling // default methods. First, there is the substitution for // the type parameters of the impl we are using and the // method we are calling. This substitution is the substs // argument we already have. // In order to compile a default method, though, we need // to consider another substitution: the substitution for // the type parameters on trait; the impl we are using // implements the trait at some particular type // parameters, and we need to substitute for those first. // So, what we need to do is find this substitution and // compose it with the one we already have. let impl_id = ty::method(tcx, def_id).container_id(); let method = ty::method(tcx, source_id); let trait_ref = ty::impl_trait_ref(tcx, impl_id) .expect("could not find trait_ref for impl with \ default methods"); // Compute the first substitution let first_subst = make_substs_for_receiver_types( tcx, impl_id, trait_ref, method); // And compose them let new_substs = first_subst.subst(tcx, &substs); let (param_vtables, self_vtables) = resolve_default_method_vtables(bcx, impl_id, method, &substs, vtables); debug!("trans_fn_with_vtables - default method: \ substs = {}, trait_subst = {}, \ first_subst = {}, new_subst = {}, \ vtables = {}, \ self_vtable = {}, param_vtables = {}", substs.repr(tcx), trait_ref.substs.repr(tcx), first_subst.repr(tcx), new_substs.repr(tcx), vtables.repr(tcx), self_vtables.repr(tcx), param_vtables.repr(tcx)); (true, source_id, new_substs, Some(self_vtables), Some(param_vtables)) } }; // Check whether this fn has an inlined copy and, if so, redirect // def_id to the local id of the inlined copy. let def_id = { if def_id.krate != ast::LOCAL_CRATE { inline::maybe_instantiate_inline(ccx, def_id) } else { def_id } }; // We must monomorphise if the fn has type parameters, is a rust // intrinsic, or is a default method. In particular, if we see an // intrinsic that is inlined from a different crate, we want to reemit the // intrinsic instead of trying to call it in the other crate. let must_monomorphise = if type_params.len() > 0 || is_default { true } else if def_id.krate == ast::LOCAL_CRATE { let map_node = session::expect( ccx.sess, ccx.tcx.map.find(def_id.node), || format!("local item should be in ast map")); match map_node { ast_map::NodeForeignItem(_) => { ccx.tcx.map.get_foreign_abis(def_id.node).is_intrinsic() } _ => false } } else { false }; // Create a monomorphic verison of generic functions if must_monomorphise { // Should be either intra-crate or inlined. assert_eq!(def_id.krate, ast::LOCAL_CRATE); let ref_id = match node { ExprId(id) if id != 0 => Some(id), _ => None }; let (val, must_cast) = monomorphize::monomorphic_fn(ccx, def_id, &substs, vtables, self_vtables, ref_id); let mut val = val; if must_cast && node != ExprId(0) { // Monotype of the REFERENCE to the function (type params // are subst'd) let ref_ty = match node { ExprId(id) => node_id_type(bcx, id), MethodCall(method_call) => { let t = bcx.ccx().maps.method_map.borrow().get().get(&method_call).ty; monomorphize_type(bcx, t) } }; val = PointerCast( bcx, val, type_of::type_of_fn_from_ty(ccx, ref_ty).ptr_to()); } return val; } // Find the actual function pointer. let mut val = { if def_id.krate == ast::LOCAL_CRATE { // Internal reference. get_item_val(ccx, def_id.node) } else { // External reference. trans_external_path(ccx, def_id, fn_tpt.ty) } }; // This is subtle and surprising, but sometimes we have to bitcast // the resulting fn pointer. The reason has to do with external // functions. If you have two crates that both bind the same C // library, they may not use precisely the same types: for // example, they will probably each declare their own structs, // which are distinct types from LLVM's point of view (nominal // types). // // Now, if those two crates are linked into an application, and // they contain inlined code, you can wind up with a situation // where both of those functions wind up being loaded into this // application simultaneously. In that case, the same function // (from LLVM's point of view) requires two types. But of course // LLVM won't allow one function to have two types. // // What we currently do, therefore, is declare the function with // one of the two types (whichever happens to come first) and then // bitcast as needed when the function is referenced to make sure // it has the type we expect. // // This can occur on either a crate-local or crate-external // reference. It also occurs when testing libcore and in some // other weird situations. Annoying. let llty = type_of::type_of_fn_from_ty(ccx, fn_tpt.ty); let llptrty = llty.ptr_to(); if val_ty(val) != llptrty { val = BitCast(bcx, val, llptrty); } val } // ______________________________________________________________________ // Translating calls pub fn trans_call<'a>( in_cx: &'a Block<'a>, call_ex: &ast::Expr, f: &ast::Expr, args: CallArgs, dest: expr::Dest) -> &'a Block<'a> { let _icx = push_ctxt("trans_call"); trans_call_inner(in_cx, Some(common::expr_info(call_ex)), expr_ty(in_cx, f), |cx, _| trans(cx, f), args, Some(dest)).bcx } pub fn trans_method_call<'a>( bcx: &'a Block<'a>, call_ex: &ast::Expr, rcvr: &ast::Expr, args: CallArgs, dest: expr::Dest) -> &'a Block<'a> { let _icx = push_ctxt("trans_method_call"); debug!("trans_method_call(call_ex={})", call_ex.repr(bcx.tcx())); let method_call = MethodCall::expr(call_ex.id); let method_ty = bcx.ccx().maps.method_map.borrow().get().get(&method_call).ty; trans_call_inner( bcx, Some(common::expr_info(call_ex)), monomorphize_type(bcx, method_ty), |cx, arg_cleanup_scope| { meth::trans_method_callee(cx, method_call, Some(rcvr), arg_cleanup_scope) }, args, Some(dest)).bcx } pub fn trans_lang_call<'a>( bcx: &'a Block<'a>, did: ast::DefId, args: &[ValueRef], dest: Option) -> Result<'a> { let fty = if did.krate == ast::LOCAL_CRATE { ty::node_id_to_type(bcx.ccx().tcx, did.node) } else { csearch::get_type(bcx.ccx().tcx, did).ty }; callee::trans_call_inner(bcx, None, fty, |bcx, _| { trans_fn_ref_with_vtables_to_callee(bcx, did, 0, [], None) }, ArgVals(args), dest) } pub fn trans_lang_call_with_type_params<'a>( bcx: &'a Block<'a>, did: ast::DefId, args: &[ValueRef], type_params: &[ty::t], dest: expr::Dest) -> &'a Block<'a> { let fty; if did.krate == ast::LOCAL_CRATE { fty = ty::node_id_to_type(bcx.tcx(), did.node); } else { fty = csearch::get_type(bcx.tcx(), did).ty; } return callee::trans_call_inner( bcx, None, fty, |bcx, _| { let callee = trans_fn_ref_with_vtables_to_callee(bcx, did, 0, type_params, None); let new_llval; match callee.data { Fn(llfn) => { let substituted = ty::subst_tps(callee.bcx.tcx(), type_params, None, fty); let llfnty = type_of::type_of(callee.bcx.ccx(), substituted); new_llval = PointerCast(callee.bcx, llfn, llfnty); } _ => fail!() } Callee { bcx: callee.bcx, data: Fn(new_llval) } }, ArgVals(args), Some(dest)).bcx; } pub fn trans_call_inner<'a>( bcx: &'a Block<'a>, call_info: Option, callee_ty: ty::t, get_callee: |bcx: &'a Block<'a>, arg_cleanup_scope: cleanup::ScopeId| -> Callee<'a>, args: CallArgs, dest: Option) -> Result<'a> { /*! * This behemoth of a function translates function calls. * Unfortunately, in order to generate more efficient LLVM * output at -O0, it has quite a complex signature (refactoring * this into two functions seems like a good idea). * * In particular, for lang items, it is invoked with a dest of * None, and in that case the return value contains the result of * the fn. The lang item must not return a structural type or else * all heck breaks loose. * * For non-lang items, `dest` is always Some, and hence the result * is written into memory somewhere. Nonetheless we return the * actual return value of the function. */ // Introduce a temporary cleanup scope that will contain cleanups // for the arguments while they are being evaluated. The purpose // this cleanup is to ensure that, should a failure occur while // evaluating argument N, the values for arguments 0...N-1 are all // cleaned up. If no failure occurs, the values are handed off to // the callee, and hence none of the cleanups in this temporary // scope will ever execute. let fcx = bcx.fcx; let ccx = fcx.ccx; let arg_cleanup_scope = fcx.push_custom_cleanup_scope(); let callee = get_callee(bcx, cleanup::CustomScope(arg_cleanup_scope)); let mut bcx = callee.bcx; let (llfn, llenv, llself) = match callee.data { Fn(llfn) => { (llfn, None, None) } TraitMethod(d) => { (d.llfn, None, Some(d.llself)) } Closure(d) => { // Closures are represented as (llfn, llclosure) pair: // load the requisite values out. let pair = d.to_llref(); let llfn = GEPi(bcx, pair, [0u, abi::fn_field_code]); let llfn = Load(bcx, llfn); let llenv = GEPi(bcx, pair, [0u, abi::fn_field_box]); let llenv = Load(bcx, llenv); (llfn, Some(llenv), None) } }; let (abi, ret_ty) = match ty::get(callee_ty).sty { ty::ty_bare_fn(ref f) => (f.abis, f.sig.output), ty::ty_closure(ref f) => (AbiSet::Rust(), f.sig.output), _ => fail!("expected bare rust fn or closure in trans_call_inner") }; let is_rust_fn = abi.is_rust() || abi.is_intrinsic(); // Generate a location to store the result. If the user does // not care about the result, just make a stack slot. let opt_llretslot = match dest { None => { assert!(!type_of::return_uses_outptr(ccx, ret_ty)); None } Some(expr::SaveIn(dst)) => Some(dst), Some(expr::Ignore) => { if !type_is_zero_size(ccx, ret_ty) { Some(alloc_ty(bcx, ret_ty, "__llret")) } else { let llty = type_of::type_of(ccx, ret_ty); Some(C_undef(llty.ptr_to())) } } }; let mut llresult = unsafe { llvm::LLVMGetUndef(Type::nil().ptr_to().to_ref()) }; // The code below invokes the function, using either the Rust // conventions (if it is a rust fn) or the native conventions // (otherwise). The important part is that, when all is sad // and done, either the return value of the function will have been // written in opt_llretslot (if it is Some) or `llresult` will be // set appropriately (otherwise). if is_rust_fn { let mut llargs = Vec::new(); // Push the out-pointer if we use an out-pointer for this // return type, otherwise push "undef". if type_of::return_uses_outptr(ccx, ret_ty) { llargs.push(opt_llretslot.unwrap()); } // Push the environment (or a trait object's self). match (llenv, llself) { (Some(llenv), None) => llargs.push(llenv), (None, Some(llself)) => llargs.push(llself), _ => {} } // Push the arguments. bcx = trans_args(bcx, args, callee_ty, &mut llargs, cleanup::CustomScope(arg_cleanup_scope), llself.is_some()); fcx.pop_custom_cleanup_scope(arg_cleanup_scope); // A function pointer is called without the declaration // available, so we have to apply any attributes with ABI // implications directly to the call instruction. Right now, // the only attribute we need to worry about is `sret`. let mut attrs = Vec::new(); if type_of::return_uses_outptr(ccx, ret_ty) { attrs.push((1, StructRetAttribute)); } // The `noalias` attribute on the return value is useful to a // function ptr caller. match ty::get(ret_ty).sty { // `~` pointer return values never alias because ownership // is transferred ty::ty_uniq(..) | ty::ty_vec(_, ty::vstore_uniq) => { attrs.push((0, NoAliasAttribute)); } _ => {} } // Invoke the actual rust fn and update bcx/llresult. let (llret, b) = base::invoke(bcx, llfn, llargs, attrs.as_slice(), call_info); bcx = b; llresult = llret; // If the Rust convention for this type is return via // the return value, copy it into llretslot. match opt_llretslot { Some(llretslot) => { if !type_of::return_uses_outptr(bcx.ccx(), ret_ty) && !type_is_zero_size(bcx.ccx(), ret_ty) { Store(bcx, llret, llretslot); } } None => {} } } else { // Lang items are the only case where dest is None, and // they are always Rust fns. assert!(dest.is_some()); let mut llargs = Vec::new(); let arg_tys = match args { ArgExprs(a) => a.iter().map(|x| expr_ty(bcx, *x)).collect(), _ => fail!("expected arg exprs.") }; bcx = trans_args(bcx, args, callee_ty, &mut llargs, cleanup::CustomScope(arg_cleanup_scope), false); fcx.pop_custom_cleanup_scope(arg_cleanup_scope); bcx = foreign::trans_native_call(bcx, callee_ty, llfn, opt_llretslot.unwrap(), llargs.as_slice(), arg_tys); } // If the caller doesn't care about the result of this fn call, // drop the temporary slot we made. match dest { None => { assert!(!type_of::return_uses_outptr(bcx.ccx(), ret_ty)); } Some(expr::Ignore) => { // drop the value if it is not being saved. bcx = glue::drop_ty(bcx, opt_llretslot.unwrap(), ret_ty); } Some(expr::SaveIn(_)) => { } } if ty::type_is_bot(ret_ty) { Unreachable(bcx); } rslt(bcx, llresult) } pub enum CallArgs<'a> { ArgExprs(&'a [@ast::Expr]), ArgOverloadedOp(Datum, Option<(Datum, ast::NodeId)>), ArgVals(&'a [ValueRef]) } fn trans_args<'a>(cx: &'a Block<'a>, args: CallArgs, fn_ty: ty::t, llargs: &mut Vec , arg_cleanup_scope: cleanup::ScopeId, ignore_self: bool) -> &'a Block<'a> { let _icx = push_ctxt("trans_args"); let arg_tys = ty::ty_fn_args(fn_ty); let variadic = ty::fn_is_variadic(fn_ty); let mut bcx = cx; // First we figure out the caller's view of the types of the arguments. // This will be needed if this is a generic call, because the callee has // to cast her view of the arguments to the caller's view. match args { ArgExprs(arg_exprs) => { let num_formal_args = arg_tys.len(); for (i, &arg_expr) in arg_exprs.iter().enumerate() { if i == 0 && ignore_self { continue; } let arg_ty = if i >= num_formal_args { assert!(variadic); expr_ty_adjusted(cx, arg_expr) } else { *arg_tys.get(i) }; let arg_datum = unpack_datum!(bcx, expr::trans(bcx, arg_expr)); llargs.push(unpack_result!(bcx, { trans_arg_datum(bcx, arg_ty, arg_datum, arg_cleanup_scope, DontAutorefArg) })); } } ArgOverloadedOp(lhs, rhs) => { assert!(!variadic); llargs.push(unpack_result!(bcx, { trans_arg_datum(bcx, *arg_tys.get(0), lhs, arg_cleanup_scope, DontAutorefArg) })); match rhs { Some((rhs, rhs_id)) => { assert_eq!(arg_tys.len(), 2); llargs.push(unpack_result!(bcx, { trans_arg_datum(bcx, *arg_tys.get(1), rhs, arg_cleanup_scope, DoAutorefArg(rhs_id)) })); } None => assert_eq!(arg_tys.len(), 1) } } ArgVals(vs) => { llargs.push_all(vs); } } bcx } pub enum AutorefArg { DontAutorefArg, DoAutorefArg(ast::NodeId) } pub fn trans_arg_datum<'a>( bcx: &'a Block<'a>, formal_arg_ty: ty::t, arg_datum: Datum, arg_cleanup_scope: cleanup::ScopeId, autoref_arg: AutorefArg) -> Result<'a> { let _icx = push_ctxt("trans_arg_datum"); let mut bcx = bcx; let ccx = bcx.ccx(); debug!("trans_arg_datum({})", formal_arg_ty.repr(bcx.tcx())); let arg_datum_ty = arg_datum.ty; debug!(" arg datum: {}", arg_datum.to_str(bcx.ccx())); let mut val; if ty::type_is_bot(arg_datum_ty) { // For values of type _|_, we generate an // "undef" value, as such a value should never // be inspected. It's important for the value // to have type lldestty (the callee's expected type). let llformal_arg_ty = type_of::type_of(ccx, formal_arg_ty); unsafe { val = llvm::LLVMGetUndef(llformal_arg_ty.to_ref()); } } else { // FIXME(#3548) use the adjustments table match autoref_arg { DoAutorefArg(arg_id) => { // We will pass argument by reference // We want an lvalue, so that we can pass by reference and let arg_datum = unpack_datum!( bcx, arg_datum.to_lvalue_datum(bcx, "arg", arg_id)); val = arg_datum.val; } DontAutorefArg => { // Make this an rvalue, since we are going to be // passing ownership. let arg_datum = unpack_datum!( bcx, arg_datum.to_rvalue_datum(bcx, "arg")); // Now that arg_datum is owned, get it into the appropriate // mode (ref vs value). let arg_datum = unpack_datum!( bcx, arg_datum.to_appropriate_datum(bcx)); // Technically, ownership of val passes to the callee. // However, we must cleanup should we fail before the // callee is actually invoked. val = arg_datum.add_clean(bcx.fcx, arg_cleanup_scope); } } if formal_arg_ty != arg_datum_ty { // this could happen due to e.g. subtyping let llformal_arg_ty = type_of::type_of_explicit_arg(ccx, formal_arg_ty); debug!("casting actual type ({}) to match formal ({})", bcx.val_to_str(val), bcx.llty_str(llformal_arg_ty)); val = PointerCast(bcx, val, llformal_arg_ty); } } debug!("--- trans_arg_datum passing {}", bcx.val_to_str(val)); rslt(bcx, val) }