1 // Copyright 2012-2014 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.
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.
11 #![allow(non_camel_case_types, non_snake_case)]
13 //! Code that is useful in various trans modules.
15 pub use self::ExprOrMethodCall::*;
19 use llvm::{ValueRef, BasicBlockRef, BuilderRef, ContextRef};
20 use llvm::{True, False, Bool};
22 use middle::lang_items::LangItem;
23 use middle::mem_categorization as mc;
26 use middle::subst::{Subst, Substs};
33 use trans::type_::Type;
36 use middle::ty::{mod, Ty};
38 use middle::ty_fold::TypeFoldable;
40 use middle::typeck::infer;
41 use util::ppaux::Repr;
42 use util::nodemap::{DefIdMap, FnvHashMap, NodeMap};
44 use arena::TypedArena;
45 use libc::{c_uint, c_char};
46 use std::c_str::ToCStr;
47 use std::cell::{Cell, RefCell};
50 use syntax::ast::Ident;
52 use syntax::ast_map::{PathElem, PathName};
53 use syntax::codemap::Span;
54 use syntax::parse::token::InternedString;
55 use syntax::parse::token;
57 pub use trans::context::CrateContext;
59 fn type_is_newtype_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
60 ty: Ty<'tcx>) -> bool {
62 ty::ty_struct(def_id, ref substs) => {
63 let fields = ty::struct_fields(ccx.tcx(), def_id, substs);
66 token::special_idents::unnamed_field.name &&
67 type_is_immediate(ccx, fields[0].mt.ty)
73 pub fn type_is_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
74 use trans::machine::llsize_of_alloc;
75 use trans::type_of::sizing_type_of;
78 let simple = ty::type_is_scalar(ty) ||
79 ty::type_is_unique(ty) || ty::type_is_region_ptr(ty) ||
80 type_is_newtype_immediate(ccx, ty) ||
81 ty::type_is_simd(tcx, ty);
82 if simple && !ty::type_is_fat_ptr(tcx, ty) {
85 if !ty::type_is_sized(tcx, ty) {
89 ty::ty_struct(..) | ty::ty_enum(..) | ty::ty_tup(..) |
90 ty::ty_unboxed_closure(..) => {
91 let llty = sizing_type_of(ccx, ty);
92 llsize_of_alloc(ccx, llty) <= llsize_of_alloc(ccx, ccx.int_type())
94 _ => type_is_zero_size(ccx, ty)
98 /// Identify types which have size zero at runtime.
99 pub fn type_is_zero_size<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
100 use trans::machine::llsize_of_alloc;
101 use trans::type_of::sizing_type_of;
102 let llty = sizing_type_of(ccx, ty);
103 llsize_of_alloc(ccx, llty) == 0
106 /// Identifies types which we declare to be equivalent to `void` in C for the purpose of function
107 /// return types. These are `()`, bot, and uninhabited enums. Note that all such types are also
108 /// zero-size, but not all zero-size types use a `void` return type (in order to aid with C ABI
110 pub fn return_type_is_void(ccx: &CrateContext, ty: Ty) -> bool {
111 ty::type_is_nil(ty) || ty::type_is_empty(ccx.tcx(), ty)
114 /// Generates a unique symbol based off the name given. This is used to create
115 /// unique symbols for things like closures.
116 pub fn gensym_name(name: &str) -> PathElem {
117 let num = token::gensym(name).uint();
118 // use one colon which will get translated to a period by the mangler, and
119 // we're guaranteed that `num` is globally unique for this crate.
120 PathName(token::gensym(format!("{}:{}", name, num).as_slice()))
123 pub struct tydesc_info<'tcx> {
125 pub tydesc: ValueRef,
132 * A note on nomenclature of linking: "extern", "foreign", and "upcall".
134 * An "extern" is an LLVM symbol we wind up emitting an undefined external
135 * reference to. This means "we don't have the thing in this compilation unit,
136 * please make sure you link it in at runtime". This could be a reference to
137 * C code found in a C library, or rust code found in a rust crate.
139 * Most "externs" are implicitly declared (automatically) as a result of a
140 * user declaring an extern _module_ dependency; this causes the rust driver
141 * to locate an extern crate, scan its compilation metadata, and emit extern
142 * declarations for any symbols used by the declaring crate.
144 * A "foreign" is an extern that references C (or other non-rust ABI) code.
145 * There is no metadata to scan for extern references so in these cases either
146 * a header-digester like bindgen, or manual function prototypes, have to
147 * serve as declarators. So these are usually given explicitly as prototype
148 * declarations, in rust code, with ABI attributes on them noting which ABI to
151 * An "upcall" is a foreign call generated by the compiler (not corresponding
152 * to any user-written call in the code) into the runtime library, to perform
153 * some helper task such as bringing a task to life, allocating memory, etc.
157 pub struct NodeInfo {
162 pub fn expr_info(expr: &ast::Expr) -> NodeInfo {
163 NodeInfo { id: expr.id, span: expr.span }
166 pub struct BuilderRef_res {
170 impl Drop for BuilderRef_res {
173 llvm::LLVMDisposeBuilder(self.b);
178 pub fn BuilderRef_res(b: BuilderRef) -> BuilderRef_res {
184 pub type ExternMap = FnvHashMap<String, ValueRef>;
186 pub fn validate_substs(substs: &Substs) {
187 assert!(substs.types.all(|t| !ty::type_needs_infer(*t)));
190 // work around bizarre resolve errors
191 pub type RvalueDatum<'tcx> = datum::Datum<'tcx, datum::Rvalue>;
192 pub type LvalueDatum<'tcx> = datum::Datum<'tcx, datum::Lvalue>;
194 // Function context. Every LLVM function we create will have one of
196 pub struct FunctionContext<'a, 'tcx: 'a> {
197 // The ValueRef returned from a call to llvm::LLVMAddFunction; the
198 // address of the first instruction in the sequence of
199 // instructions for this function that will go in the .text
200 // section of the executable we're generating.
203 // The environment argument in a closure.
204 pub llenv: Option<ValueRef>,
206 // A pointer to where to store the return value. If the return type is
207 // immediate, this points to an alloca in the function. Otherwise, it's a
208 // pointer to the hidden first parameter of the function. After function
209 // construction, this should always be Some.
210 pub llretslotptr: Cell<Option<ValueRef>>,
212 // These pub elements: "hoisted basic blocks" containing
213 // administrative activities that have to happen in only one place in
214 // the function, due to LLVM's quirks.
215 // A marker for the place where we want to insert the function's static
216 // allocas, so that LLVM will coalesce them into a single alloca call.
217 pub alloca_insert_pt: Cell<Option<ValueRef>>,
218 pub llreturn: Cell<Option<BasicBlockRef>>,
220 // If the function has any nested return's, including something like:
221 // fn foo() -> Option<Foo> { Some(Foo { x: return None }) }, then
222 // we use a separate alloca for each return
223 pub needs_ret_allocas: bool,
225 // The a value alloca'd for calls to upcalls.rust_personality. Used when
226 // outputting the resume instruction.
227 pub personality: Cell<Option<ValueRef>>,
229 // True if the caller expects this fn to use the out pointer to
230 // return. Either way, your code should write into the slot llretslotptr
231 // points to, but if this value is false, that slot will be a local alloca.
232 pub caller_expects_out_pointer: bool,
234 // Maps the DefId's for local variables to the allocas created for
235 // them in llallocas.
236 pub lllocals: RefCell<NodeMap<LvalueDatum<'tcx>>>,
238 // Same as above, but for closure upvars
239 pub llupvars: RefCell<NodeMap<ValueRef>>,
241 // The NodeId of the function, or -1 if it doesn't correspond to
242 // a user-defined function.
245 // If this function is being monomorphized, this contains the type
246 // substitutions used.
247 pub param_substs: &'a Substs<'tcx>,
249 // The source span and nesting context where this function comes from, for
250 // error reporting and symbol generation.
251 pub span: Option<Span>,
253 // The arena that blocks are allocated from.
254 pub block_arena: &'a TypedArena<BlockS<'a, 'tcx>>,
256 // This function's enclosing crate context.
257 pub ccx: &'a CrateContext<'a, 'tcx>,
259 // Used and maintained by the debuginfo module.
260 pub debug_context: debuginfo::FunctionDebugContext,
263 pub scopes: RefCell<Vec<cleanup::CleanupScope<'a, 'tcx>>>,
266 impl<'a, 'tcx> FunctionContext<'a, 'tcx> {
267 pub fn arg_pos(&self, arg: uint) -> uint {
268 let arg = self.env_arg_pos() + arg;
269 if self.llenv.is_some() {
276 pub fn out_arg_pos(&self) -> uint {
277 assert!(self.caller_expects_out_pointer);
281 pub fn env_arg_pos(&self) -> uint {
282 if self.caller_expects_out_pointer {
289 pub fn cleanup(&self) {
291 llvm::LLVMInstructionEraseFromParent(self.alloca_insert_pt
297 pub fn get_llreturn(&self) -> BasicBlockRef {
298 if self.llreturn.get().is_none() {
300 self.llreturn.set(Some(unsafe {
301 "return".with_c_str(|buf| {
302 llvm::LLVMAppendBasicBlockInContext(self.ccx.llcx(), self.llfn, buf)
307 self.llreturn.get().unwrap()
310 pub fn get_ret_slot(&self, bcx: Block<'a, 'tcx>,
311 output: ty::FnOutput<'tcx>,
312 name: &str) -> ValueRef {
313 if self.needs_ret_allocas {
314 base::alloca_no_lifetime(bcx, match output {
315 ty::FnConverging(output_type) => type_of::type_of(bcx.ccx(), output_type),
316 ty::FnDiverging => Type::void(bcx.ccx())
319 self.llretslotptr.get().unwrap()
323 pub fn new_block(&'a self,
326 opt_node_id: Option<ast::NodeId>)
329 let llbb = name.with_c_str(|buf| {
330 llvm::LLVMAppendBasicBlockInContext(self.ccx.llcx(),
334 BlockS::new(llbb, is_lpad, opt_node_id, self)
338 pub fn new_id_block(&'a self,
340 node_id: ast::NodeId)
342 self.new_block(false, name, Some(node_id))
345 pub fn new_temp_block(&'a self,
348 self.new_block(false, name, None)
351 pub fn join_blocks(&'a self,
353 in_cxs: &[Block<'a, 'tcx>])
355 let out = self.new_id_block("join", id);
356 let mut reachable = false;
357 for bcx in in_cxs.iter() {
358 if !bcx.unreachable.get() {
359 build::Br(*bcx, out.llbb);
364 build::Unreachable(out);
370 // Basic block context. We create a block context for each basic block
371 // (single-entry, single-exit sequence of instructions) we generate from Rust
372 // code. Each basic block we generate is attached to a function, typically
373 // with many basic blocks per function. All the basic blocks attached to a
374 // function are organized as a directed graph.
375 pub struct BlockS<'blk, 'tcx: 'blk> {
376 // The BasicBlockRef returned from a call to
377 // llvm::LLVMAppendBasicBlock(llfn, name), which adds a basic
378 // block to the function pointed to by llfn. We insert
379 // instructions into that block by way of this block context.
380 // The block pointing to this one in the function's digraph.
381 pub llbb: BasicBlockRef,
382 pub terminated: Cell<bool>,
383 pub unreachable: Cell<bool>,
385 // Is this block part of a landing pad?
388 // AST node-id associated with this block, if any. Used for
389 // debugging purposes only.
390 pub opt_node_id: Option<ast::NodeId>,
392 // The function context for the function to which this block is
394 pub fcx: &'blk FunctionContext<'blk, 'tcx>,
397 pub type Block<'blk, 'tcx> = &'blk BlockS<'blk, 'tcx>;
399 impl<'blk, 'tcx> BlockS<'blk, 'tcx> {
400 pub fn new(llbb: BasicBlockRef,
402 opt_node_id: Option<ast::NodeId>,
403 fcx: &'blk FunctionContext<'blk, 'tcx>)
404 -> Block<'blk, 'tcx> {
405 fcx.block_arena.alloc(BlockS {
407 terminated: Cell::new(false),
408 unreachable: Cell::new(false),
410 opt_node_id: opt_node_id,
415 pub fn ccx(&self) -> &'blk CrateContext<'blk, 'tcx> {
418 pub fn tcx(&self) -> &'blk ty::ctxt<'tcx> {
421 pub fn sess(&self) -> &'blk Session { self.fcx.ccx.sess() }
423 pub fn ident(&self, ident: Ident) -> String {
424 token::get_ident(ident).get().to_string()
427 pub fn node_id_to_string(&self, id: ast::NodeId) -> String {
428 self.tcx().map.node_to_string(id).to_string()
431 pub fn expr_to_string(&self, e: &ast::Expr) -> String {
435 pub fn def(&self, nid: ast::NodeId) -> def::Def {
436 match self.tcx().def_map.borrow().get(&nid) {
437 Some(v) => v.clone(),
439 self.tcx().sess.bug(format!(
440 "no def associated with node id {}", nid).as_slice());
445 pub fn val_to_string(&self, val: ValueRef) -> String {
446 self.ccx().tn().val_to_string(val)
449 pub fn llty_str(&self, ty: Type) -> String {
450 self.ccx().tn().type_to_string(ty)
453 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
457 pub fn to_str(&self) -> String {
458 format!("[block {:p}]", self)
462 impl<'blk, 'tcx> mc::Typer<'tcx> for BlockS<'blk, 'tcx> {
463 fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx> {
467 fn node_ty(&self, id: ast::NodeId) -> mc::McResult<Ty<'tcx>> {
468 Ok(node_id_type(self, id))
471 fn node_method_ty(&self, method_call: typeck::MethodCall) -> Option<Ty<'tcx>> {
476 .map(|method| monomorphize_type(self, method.ty))
479 fn adjustments<'a>(&'a self) -> &'a RefCell<NodeMap<ty::AutoAdjustment<'tcx>>> {
480 &self.tcx().adjustments
483 fn is_method_call(&self, id: ast::NodeId) -> bool {
484 self.tcx().method_map.borrow().contains_key(&typeck::MethodCall::expr(id))
487 fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<region::CodeExtent> {
488 self.tcx().region_maps.temporary_scope(rvalue_id)
491 fn unboxed_closures<'a>(&'a self)
492 -> &'a RefCell<DefIdMap<ty::UnboxedClosure<'tcx>>> {
493 &self.tcx().unboxed_closures
496 fn upvar_borrow(&self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow {
497 self.tcx().upvar_borrow_map.borrow()[upvar_id].clone()
500 fn capture_mode(&self, closure_expr_id: ast::NodeId)
501 -> ast::CaptureClause {
502 self.tcx().capture_modes.borrow()[closure_expr_id].clone()
506 pub struct Result<'blk, 'tcx: 'blk> {
507 pub bcx: Block<'blk, 'tcx>,
511 impl<'b, 'tcx> Result<'b, 'tcx> {
512 pub fn new(bcx: Block<'b, 'tcx>, val: ValueRef) -> Result<'b, 'tcx> {
520 pub fn val_ty(v: ValueRef) -> Type {
522 Type::from_ref(llvm::LLVMTypeOf(v))
526 // LLVM constant constructors.
527 pub fn C_null(t: Type) -> ValueRef {
529 llvm::LLVMConstNull(t.to_ref())
533 pub fn C_undef(t: Type) -> ValueRef {
535 llvm::LLVMGetUndef(t.to_ref())
539 pub fn C_integral(t: Type, u: u64, sign_extend: bool) -> ValueRef {
541 llvm::LLVMConstInt(t.to_ref(), u, sign_extend as Bool)
545 pub fn C_floating(s: &str, t: Type) -> ValueRef {
547 s.with_c_str(|buf| llvm::LLVMConstRealOfString(t.to_ref(), buf))
551 pub fn C_nil(ccx: &CrateContext) -> ValueRef {
552 C_struct(ccx, &[], false)
555 pub fn C_bool(ccx: &CrateContext, val: bool) -> ValueRef {
556 C_integral(Type::i1(ccx), val as u64, false)
559 pub fn C_i32(ccx: &CrateContext, i: i32) -> ValueRef {
560 C_integral(Type::i32(ccx), i as u64, true)
563 pub fn C_i64(ccx: &CrateContext, i: i64) -> ValueRef {
564 C_integral(Type::i64(ccx), i as u64, true)
567 pub fn C_u64(ccx: &CrateContext, i: u64) -> ValueRef {
568 C_integral(Type::i64(ccx), i, false)
571 pub fn C_int<I: AsI64>(ccx: &CrateContext, i: I) -> ValueRef {
574 match machine::llbitsize_of_real(ccx, ccx.int_type()) {
575 32 => assert!(v < (1<<31) && v >= -(1<<31)),
577 n => panic!("unsupported target size: {}", n)
580 C_integral(ccx.int_type(), v as u64, true)
583 pub fn C_uint<I: AsU64>(ccx: &CrateContext, i: I) -> ValueRef {
586 match machine::llbitsize_of_real(ccx, ccx.int_type()) {
587 32 => assert!(v < (1<<32)),
589 n => panic!("unsupported target size: {}", n)
592 C_integral(ccx.int_type(), v, false)
595 pub trait AsI64 { fn as_i64(self) -> i64; }
596 pub trait AsU64 { fn as_u64(self) -> u64; }
598 // FIXME: remove the intptr conversions, because they
599 // are host-architecture-dependent
600 impl AsI64 for i64 { fn as_i64(self) -> i64 { self as i64 }}
601 impl AsI64 for i32 { fn as_i64(self) -> i64 { self as i64 }}
602 impl AsI64 for int { fn as_i64(self) -> i64 { self as i64 }}
604 impl AsU64 for u64 { fn as_u64(self) -> u64 { self as u64 }}
605 impl AsU64 for u32 { fn as_u64(self) -> u64 { self as u64 }}
606 impl AsU64 for uint { fn as_u64(self) -> u64 { self as u64 }}
608 pub fn C_u8(ccx: &CrateContext, i: uint) -> ValueRef {
609 C_integral(Type::i8(ccx), i as u64, false)
613 // This is a 'c-like' raw string, which differs from
614 // our boxed-and-length-annotated strings.
615 pub fn C_cstr(cx: &CrateContext, s: InternedString, null_terminated: bool) -> ValueRef {
617 match cx.const_cstr_cache().borrow().get(&s) {
618 Some(&llval) => return llval,
622 let sc = llvm::LLVMConstStringInContext(cx.llcx(),
623 s.get().as_ptr() as *const c_char,
624 s.get().len() as c_uint,
625 !null_terminated as Bool);
627 let gsym = token::gensym("str");
628 let g = format!("str{}", gsym.uint()).with_c_str(|buf| {
629 llvm::LLVMAddGlobal(cx.llmod(), val_ty(sc).to_ref(), buf)
631 llvm::LLVMSetInitializer(g, sc);
632 llvm::LLVMSetGlobalConstant(g, True);
633 llvm::SetLinkage(g, llvm::InternalLinkage);
635 cx.const_cstr_cache().borrow_mut().insert(s, g);
640 // NB: Do not use `do_spill_noroot` to make this into a constant string, or
641 // you will be kicked off fast isel. See issue #4352 for an example of this.
642 pub fn C_str_slice(cx: &CrateContext, s: InternedString) -> ValueRef {
644 let len = s.get().len();
645 let cs = llvm::LLVMConstPointerCast(C_cstr(cx, s, false),
646 Type::i8p(cx).to_ref());
647 C_named_struct(cx.tn().find_type("str_slice").unwrap(), &[cs, C_uint(cx, len)])
651 pub fn C_binary_slice(cx: &CrateContext, data: &[u8]) -> ValueRef {
653 let len = data.len();
654 let lldata = C_bytes(cx, data);
656 let gsym = token::gensym("binary");
657 let g = format!("binary{}", gsym.uint()).with_c_str(|buf| {
658 llvm::LLVMAddGlobal(cx.llmod(), val_ty(lldata).to_ref(), buf)
660 llvm::LLVMSetInitializer(g, lldata);
661 llvm::LLVMSetGlobalConstant(g, True);
662 llvm::SetLinkage(g, llvm::InternalLinkage);
664 let cs = llvm::LLVMConstPointerCast(g, Type::i8p(cx).to_ref());
665 C_struct(cx, &[cs, C_uint(cx, len)], false)
669 pub fn C_struct(cx: &CrateContext, elts: &[ValueRef], packed: bool) -> ValueRef {
670 C_struct_in_context(cx.llcx(), elts, packed)
673 pub fn C_struct_in_context(llcx: ContextRef, elts: &[ValueRef], packed: bool) -> ValueRef {
675 llvm::LLVMConstStructInContext(llcx,
676 elts.as_ptr(), elts.len() as c_uint,
681 pub fn C_named_struct(t: Type, elts: &[ValueRef]) -> ValueRef {
683 llvm::LLVMConstNamedStruct(t.to_ref(), elts.as_ptr(), elts.len() as c_uint)
687 pub fn C_array(ty: Type, elts: &[ValueRef]) -> ValueRef {
689 return llvm::LLVMConstArray(ty.to_ref(), elts.as_ptr(), elts.len() as c_uint);
693 pub fn C_bytes(cx: &CrateContext, bytes: &[u8]) -> ValueRef {
694 C_bytes_in_context(cx.llcx(), bytes)
697 pub fn C_bytes_in_context(llcx: ContextRef, bytes: &[u8]) -> ValueRef {
699 let ptr = bytes.as_ptr() as *const c_char;
700 return llvm::LLVMConstStringInContext(llcx, ptr, bytes.len() as c_uint, True);
704 pub fn const_get_elt(cx: &CrateContext, v: ValueRef, us: &[c_uint])
707 let r = llvm::LLVMConstExtractValue(v, us.as_ptr(), us.len() as c_uint);
709 debug!("const_get_elt(v={}, us={}, r={})",
710 cx.tn().val_to_string(v), us, cx.tn().val_to_string(r));
716 pub fn is_const(v: ValueRef) -> bool {
718 llvm::LLVMIsConstant(v) == True
722 pub fn const_to_int(v: ValueRef) -> i64 {
724 llvm::LLVMConstIntGetSExtValue(v)
728 pub fn const_to_uint(v: ValueRef) -> u64 {
730 llvm::LLVMConstIntGetZExtValue(v)
734 pub fn is_undef(val: ValueRef) -> bool {
736 llvm::LLVMIsUndef(val) != False
740 pub fn is_null(val: ValueRef) -> bool {
742 llvm::LLVMIsNull(val) != False
746 pub fn monomorphize_type<'blk, 'tcx>(bcx: &BlockS<'blk, 'tcx>, t: Ty<'tcx>) -> Ty<'tcx> {
747 t.subst(bcx.tcx(), bcx.fcx.param_substs)
750 pub fn node_id_type<'blk, 'tcx>(bcx: &BlockS<'blk, 'tcx>, id: ast::NodeId) -> Ty<'tcx> {
752 let t = ty::node_id_to_type(tcx, id);
753 monomorphize_type(bcx, t)
756 pub fn expr_ty<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, ex: &ast::Expr) -> Ty<'tcx> {
757 node_id_type(bcx, ex.id)
760 pub fn expr_ty_adjusted<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, ex: &ast::Expr) -> Ty<'tcx> {
761 monomorphize_type(bcx, ty::expr_ty_adjusted(bcx.tcx(), ex))
764 /// Attempts to resolve an obligation. The result is a shallow vtable resolution -- meaning that we
765 /// do not (necessarily) resolve all nested obligations on the impl. Note that type check should
766 /// guarantee to us that all nested obligations *could be* resolved if we wanted to.
767 pub fn fulfill_obligation<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
769 trait_ref: Rc<ty::TraitRef<'tcx>>)
770 -> traits::Vtable<'tcx, ()>
774 // Remove any references to regions; this helps improve caching.
775 let trait_ref = ty_fold::erase_regions(tcx, trait_ref);
777 // First check the cache.
778 match ccx.trait_cache().borrow().get(&trait_ref) {
780 info!("Cache hit: {}", trait_ref.repr(ccx.tcx()));
781 return (*vtable).clone();
786 debug!("trans fulfill_obligation: trait_ref={}", trait_ref.repr(ccx.tcx()));
788 ty::populate_implementations_for_trait_if_necessary(tcx, trait_ref.def_id);
789 let infcx = infer::new_infer_ctxt(tcx);
791 // Parameter environment is used to give details about type parameters,
792 // but since we are in trans, everything is fully monomorphized.
793 let param_env = ty::empty_parameter_environment();
795 // Do the initial selection for the obligation. This yields the
796 // shallow result we are looking for -- that is, what specific impl.
797 let mut selcx = traits::SelectionContext::new(&infcx, ¶m_env, tcx);
798 let obligation = traits::Obligation::misc(span, trait_ref.clone());
799 let selection = match selcx.select(&obligation) {
800 Ok(Some(selection)) => selection,
802 // Ambiguity can happen when monomorphizing during trans
803 // expands to some humongo type that never occurred
804 // statically -- this humongo type can then overflow,
805 // leading to an ambiguous result. So report this as an
806 // overflow bug, since I believe this is the only case
807 // where ambiguity can result.
808 debug!("Encountered ambiguity selecting `{}` during trans, \
809 presuming due to overflow",
810 trait_ref.repr(tcx));
811 ccx.sess().span_fatal(
813 "reached the recursion limit during monomorphization");
818 format!("Encountered error `{}` selecting `{}` during trans",
820 trait_ref.repr(tcx)).as_slice())
824 // Currently, we use a fulfillment context to completely resolve
825 // all nested obligations. This is because they can inform the
826 // inference of the impl's type parameters. However, in principle,
827 // we only need to do this until the impl's type parameters are
828 // fully bound. It could be a slight optimization to stop
830 let mut fulfill_cx = traits::FulfillmentContext::new();
831 let vtable = selection.map_move_nested(|obligation| {
832 fulfill_cx.register_obligation(tcx, obligation);
834 match fulfill_cx.select_all_or_error(&infcx, ¶m_env, tcx) {
837 if errors.iter().all(|e| e.is_overflow()) {
838 // See Ok(None) case above.
839 ccx.sess().span_fatal(
841 "reached the recursion limit during monomorphization");
845 format!("Encountered errors `{}` fulfilling `{}` during trans",
847 trait_ref.repr(tcx)).as_slice());
852 // Use skolemize to simultaneously replace all type variables with
853 // their bindings and replace all regions with 'static. This is
854 // sort of overkill because we do not expect there to be any
855 // unbound type variables, hence no skolemized types should ever
857 let vtable = vtable.fold_with(&mut infcx.skolemizer());
859 info!("Cache miss: {}", trait_ref.repr(ccx.tcx()));
860 ccx.trait_cache().borrow_mut().insert(trait_ref,
866 // Key used to lookup values supplied for type parameters in an expr.
867 #[deriving(PartialEq, Show)]
868 pub enum ExprOrMethodCall {
869 // Type parameters for a path like `None::<int>`
872 // Type parameters for a method call like `a.foo::<int>()`
873 MethodCall(typeck::MethodCall)
876 pub fn node_id_substs<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
877 node: ExprOrMethodCall)
878 -> subst::Substs<'tcx>
882 let substs = match node {
884 ty::node_id_item_substs(tcx, id).substs
886 MethodCall(method_call) => {
887 (*tcx.method_map.borrow())[method_call].substs.clone()
891 if substs.types.any(|t| ty::type_needs_infer(*t)) {
893 format!("type parameters for node {} include inference types: \
896 substs.repr(bcx.tcx())).as_slice());
899 let substs = substs.erase_regions();
900 substs.subst(tcx, bcx.fcx.param_substs)
903 pub fn langcall(bcx: Block,
908 match bcx.tcx().lang_items.require(li) {
911 let msg = format!("{} {}", msg, s);
913 Some(span) => bcx.tcx().sess.span_fatal(span, msg.as_slice()),
914 None => bcx.tcx().sess.fatal(msg.as_slice()),