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};
23 use middle::lang_items::LangItem;
24 use middle::mem_categorization as mc;
27 use middle::subst::{Subst, Substs};
34 use trans::type_::Type;
37 use middle::ty::{mod, Ty};
39 use middle::ty_fold::TypeFoldable;
40 use util::ppaux::Repr;
41 use util::nodemap::{DefIdMap, FnvHashMap, NodeMap};
43 use arena::TypedArena;
44 use libc::{c_uint, c_char};
45 use std::c_str::ToCStr;
46 use std::cell::{Cell, RefCell};
49 use syntax::ast::Ident;
51 use syntax::ast_map::{PathElem, PathName};
52 use syntax::codemap::Span;
53 use syntax::parse::token::InternedString;
54 use syntax::parse::token;
56 pub use trans::context::CrateContext;
58 fn type_is_newtype_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
59 ty: Ty<'tcx>) -> bool {
61 ty::ty_struct(def_id, ref substs) => {
62 let fields = ty::struct_fields(ccx.tcx(), def_id, substs);
65 token::special_idents::unnamed_field.name &&
66 type_is_immediate(ccx, fields[0].mt.ty)
72 pub fn type_is_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
73 use trans::machine::llsize_of_alloc;
74 use trans::type_of::sizing_type_of;
77 let simple = ty::type_is_scalar(ty) ||
78 ty::type_is_unique(ty) || ty::type_is_region_ptr(ty) ||
79 type_is_newtype_immediate(ccx, ty) ||
80 ty::type_is_simd(tcx, ty);
81 if simple && !ty::type_is_fat_ptr(tcx, ty) {
84 if !ty::type_is_sized(tcx, ty) {
88 ty::ty_struct(..) | ty::ty_enum(..) | ty::ty_tup(..) |
89 ty::ty_unboxed_closure(..) => {
90 let llty = sizing_type_of(ccx, ty);
91 llsize_of_alloc(ccx, llty) <= llsize_of_alloc(ccx, ccx.int_type())
93 _ => type_is_zero_size(ccx, ty)
97 /// Identify types which have size zero at runtime.
98 pub fn type_is_zero_size<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
99 use trans::machine::llsize_of_alloc;
100 use trans::type_of::sizing_type_of;
101 let llty = sizing_type_of(ccx, ty);
102 llsize_of_alloc(ccx, llty) == 0
105 /// Identifies types which we declare to be equivalent to `void` in C for the purpose of function
106 /// return types. These are `()`, bot, and uninhabited enums. Note that all such types are also
107 /// zero-size, but not all zero-size types use a `void` return type (in order to aid with C ABI
109 pub fn return_type_is_void(ccx: &CrateContext, ty: Ty) -> bool {
110 ty::type_is_nil(ty) || ty::type_is_empty(ccx.tcx(), ty)
113 /// Generates a unique symbol based off the name given. This is used to create
114 /// unique symbols for things like closures.
115 pub fn gensym_name(name: &str) -> PathElem {
116 let num = token::gensym(name).uint();
117 // use one colon which will get translated to a period by the mangler, and
118 // we're guaranteed that `num` is globally unique for this crate.
119 PathName(token::gensym(format!("{}:{}", name, num).as_slice()))
122 pub struct tydesc_info<'tcx> {
124 pub tydesc: ValueRef,
131 * A note on nomenclature of linking: "extern", "foreign", and "upcall".
133 * An "extern" is an LLVM symbol we wind up emitting an undefined external
134 * reference to. This means "we don't have the thing in this compilation unit,
135 * please make sure you link it in at runtime". This could be a reference to
136 * C code found in a C library, or rust code found in a rust crate.
138 * Most "externs" are implicitly declared (automatically) as a result of a
139 * user declaring an extern _module_ dependency; this causes the rust driver
140 * to locate an extern crate, scan its compilation metadata, and emit extern
141 * declarations for any symbols used by the declaring crate.
143 * A "foreign" is an extern that references C (or other non-rust ABI) code.
144 * There is no metadata to scan for extern references so in these cases either
145 * a header-digester like bindgen, or manual function prototypes, have to
146 * serve as declarators. So these are usually given explicitly as prototype
147 * declarations, in rust code, with ABI attributes on them noting which ABI to
150 * An "upcall" is a foreign call generated by the compiler (not corresponding
151 * to any user-written call in the code) into the runtime library, to perform
152 * some helper task such as bringing a task to life, allocating memory, etc.
156 pub struct NodeInfo {
161 pub fn expr_info(expr: &ast::Expr) -> NodeInfo {
162 NodeInfo { id: expr.id, span: expr.span }
165 pub struct BuilderRef_res {
169 impl Drop for BuilderRef_res {
172 llvm::LLVMDisposeBuilder(self.b);
177 pub fn BuilderRef_res(b: BuilderRef) -> BuilderRef_res {
183 pub type ExternMap = FnvHashMap<String, ValueRef>;
185 pub fn validate_substs(substs: &Substs) {
186 assert!(substs.types.all(|t| !ty::type_needs_infer(*t)));
189 // work around bizarre resolve errors
190 pub type RvalueDatum<'tcx> = datum::Datum<'tcx, datum::Rvalue>;
191 pub type LvalueDatum<'tcx> = datum::Datum<'tcx, datum::Lvalue>;
193 // Function context. Every LLVM function we create will have one of
195 pub struct FunctionContext<'a, 'tcx: 'a> {
196 // The ValueRef returned from a call to llvm::LLVMAddFunction; the
197 // address of the first instruction in the sequence of
198 // instructions for this function that will go in the .text
199 // section of the executable we're generating.
202 // The environment argument in a closure.
203 pub llenv: Option<ValueRef>,
205 // A pointer to where to store the return value. If the return type is
206 // immediate, this points to an alloca in the function. Otherwise, it's a
207 // pointer to the hidden first parameter of the function. After function
208 // construction, this should always be Some.
209 pub llretslotptr: Cell<Option<ValueRef>>,
211 // These pub elements: "hoisted basic blocks" containing
212 // administrative activities that have to happen in only one place in
213 // the function, due to LLVM's quirks.
214 // A marker for the place where we want to insert the function's static
215 // allocas, so that LLVM will coalesce them into a single alloca call.
216 pub alloca_insert_pt: Cell<Option<ValueRef>>,
217 pub llreturn: Cell<Option<BasicBlockRef>>,
219 // If the function has any nested return's, including something like:
220 // fn foo() -> Option<Foo> { Some(Foo { x: return None }) }, then
221 // we use a separate alloca for each return
222 pub needs_ret_allocas: bool,
224 // The a value alloca'd for calls to upcalls.rust_personality. Used when
225 // outputting the resume instruction.
226 pub personality: Cell<Option<ValueRef>>,
228 // True if the caller expects this fn to use the out pointer to
229 // return. Either way, your code should write into the slot llretslotptr
230 // points to, but if this value is false, that slot will be a local alloca.
231 pub caller_expects_out_pointer: bool,
233 // Maps the DefId's for local variables to the allocas created for
234 // them in llallocas.
235 pub lllocals: RefCell<NodeMap<LvalueDatum<'tcx>>>,
237 // Same as above, but for closure upvars
238 pub llupvars: RefCell<NodeMap<ValueRef>>,
240 // The NodeId of the function, or -1 if it doesn't correspond to
241 // a user-defined function.
244 // If this function is being monomorphized, this contains the type
245 // substitutions used.
246 pub param_substs: &'a Substs<'tcx>,
248 // The source span and nesting context where this function comes from, for
249 // error reporting and symbol generation.
250 pub span: Option<Span>,
252 // The arena that blocks are allocated from.
253 pub block_arena: &'a TypedArena<BlockS<'a, 'tcx>>,
255 // This function's enclosing crate context.
256 pub ccx: &'a CrateContext<'a, 'tcx>,
258 // Used and maintained by the debuginfo module.
259 pub debug_context: debuginfo::FunctionDebugContext,
262 pub scopes: RefCell<Vec<cleanup::CleanupScope<'a, 'tcx>>>,
265 impl<'a, 'tcx> FunctionContext<'a, 'tcx> {
266 pub fn arg_pos(&self, arg: uint) -> uint {
267 let arg = self.env_arg_pos() + arg;
268 if self.llenv.is_some() {
275 pub fn env_arg_pos(&self) -> uint {
276 if self.caller_expects_out_pointer {
283 pub fn cleanup(&self) {
285 llvm::LLVMInstructionEraseFromParent(self.alloca_insert_pt
291 pub fn get_llreturn(&self) -> BasicBlockRef {
292 if self.llreturn.get().is_none() {
294 self.llreturn.set(Some(unsafe {
295 "return".with_c_str(|buf| {
296 llvm::LLVMAppendBasicBlockInContext(self.ccx.llcx(), self.llfn, buf)
301 self.llreturn.get().unwrap()
304 pub fn get_ret_slot(&self, bcx: Block<'a, 'tcx>,
305 output: ty::FnOutput<'tcx>,
306 name: &str) -> ValueRef {
307 if self.needs_ret_allocas {
308 base::alloca_no_lifetime(bcx, match output {
309 ty::FnConverging(output_type) => type_of::type_of(bcx.ccx(), output_type),
310 ty::FnDiverging => Type::void(bcx.ccx())
313 self.llretslotptr.get().unwrap()
317 pub fn new_block(&'a self,
320 opt_node_id: Option<ast::NodeId>)
323 let llbb = name.with_c_str(|buf| {
324 llvm::LLVMAppendBasicBlockInContext(self.ccx.llcx(),
328 BlockS::new(llbb, is_lpad, opt_node_id, self)
332 pub fn new_id_block(&'a self,
334 node_id: ast::NodeId)
336 self.new_block(false, name, Some(node_id))
339 pub fn new_temp_block(&'a self,
342 self.new_block(false, name, None)
345 pub fn join_blocks(&'a self,
347 in_cxs: &[Block<'a, 'tcx>])
349 let out = self.new_id_block("join", id);
350 let mut reachable = false;
351 for bcx in in_cxs.iter() {
352 if !bcx.unreachable.get() {
353 build::Br(*bcx, out.llbb);
358 build::Unreachable(out);
364 // Basic block context. We create a block context for each basic block
365 // (single-entry, single-exit sequence of instructions) we generate from Rust
366 // code. Each basic block we generate is attached to a function, typically
367 // with many basic blocks per function. All the basic blocks attached to a
368 // function are organized as a directed graph.
369 pub struct BlockS<'blk, 'tcx: 'blk> {
370 // The BasicBlockRef returned from a call to
371 // llvm::LLVMAppendBasicBlock(llfn, name), which adds a basic
372 // block to the function pointed to by llfn. We insert
373 // instructions into that block by way of this block context.
374 // The block pointing to this one in the function's digraph.
375 pub llbb: BasicBlockRef,
376 pub terminated: Cell<bool>,
377 pub unreachable: Cell<bool>,
379 // Is this block part of a landing pad?
382 // AST node-id associated with this block, if any. Used for
383 // debugging purposes only.
384 pub opt_node_id: Option<ast::NodeId>,
386 // The function context for the function to which this block is
388 pub fcx: &'blk FunctionContext<'blk, 'tcx>,
391 pub type Block<'blk, 'tcx> = &'blk BlockS<'blk, 'tcx>;
393 impl<'blk, 'tcx> BlockS<'blk, 'tcx> {
394 pub fn new(llbb: BasicBlockRef,
396 opt_node_id: Option<ast::NodeId>,
397 fcx: &'blk FunctionContext<'blk, 'tcx>)
398 -> Block<'blk, 'tcx> {
399 fcx.block_arena.alloc(BlockS {
401 terminated: Cell::new(false),
402 unreachable: Cell::new(false),
404 opt_node_id: opt_node_id,
409 pub fn ccx(&self) -> &'blk CrateContext<'blk, 'tcx> {
412 pub fn tcx(&self) -> &'blk ty::ctxt<'tcx> {
415 pub fn sess(&self) -> &'blk Session { self.fcx.ccx.sess() }
417 pub fn ident(&self, ident: Ident) -> String {
418 token::get_ident(ident).get().to_string()
421 pub fn node_id_to_string(&self, id: ast::NodeId) -> String {
422 self.tcx().map.node_to_string(id).to_string()
425 pub fn expr_to_string(&self, e: &ast::Expr) -> String {
429 pub fn def(&self, nid: ast::NodeId) -> def::Def {
430 match self.tcx().def_map.borrow().get(&nid) {
431 Some(v) => v.clone(),
433 self.tcx().sess.bug(format!(
434 "no def associated with node id {}", nid).as_slice());
439 pub fn val_to_string(&self, val: ValueRef) -> String {
440 self.ccx().tn().val_to_string(val)
443 pub fn llty_str(&self, ty: Type) -> String {
444 self.ccx().tn().type_to_string(ty)
447 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
451 pub fn to_str(&self) -> String {
452 format!("[block {:p}]", self)
456 impl<'blk, 'tcx> mc::Typer<'tcx> for BlockS<'blk, 'tcx> {
457 fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx> {
461 fn node_ty(&self, id: ast::NodeId) -> mc::McResult<Ty<'tcx>> {
462 Ok(node_id_type(self, id))
465 fn node_method_ty(&self, method_call: ty::MethodCall) -> Option<Ty<'tcx>> {
470 .map(|method| monomorphize_type(self, method.ty))
473 fn adjustments<'a>(&'a self) -> &'a RefCell<NodeMap<ty::AutoAdjustment<'tcx>>> {
474 &self.tcx().adjustments
477 fn is_method_call(&self, id: ast::NodeId) -> bool {
478 self.tcx().method_map.borrow().contains_key(&ty::MethodCall::expr(id))
481 fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<region::CodeExtent> {
482 self.tcx().region_maps.temporary_scope(rvalue_id)
485 fn unboxed_closures<'a>(&'a self)
486 -> &'a RefCell<DefIdMap<ty::UnboxedClosure<'tcx>>> {
487 &self.tcx().unboxed_closures
490 fn upvar_borrow(&self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow {
491 self.tcx().upvar_borrow_map.borrow()[upvar_id].clone()
494 fn capture_mode(&self, closure_expr_id: ast::NodeId)
495 -> ast::CaptureClause {
496 self.tcx().capture_modes.borrow()[closure_expr_id].clone()
500 pub struct Result<'blk, 'tcx: 'blk> {
501 pub bcx: Block<'blk, 'tcx>,
505 impl<'b, 'tcx> Result<'b, 'tcx> {
506 pub fn new(bcx: Block<'b, 'tcx>, val: ValueRef) -> Result<'b, 'tcx> {
514 pub fn val_ty(v: ValueRef) -> Type {
516 Type::from_ref(llvm::LLVMTypeOf(v))
520 // LLVM constant constructors.
521 pub fn C_null(t: Type) -> ValueRef {
523 llvm::LLVMConstNull(t.to_ref())
527 pub fn C_undef(t: Type) -> ValueRef {
529 llvm::LLVMGetUndef(t.to_ref())
533 pub fn C_integral(t: Type, u: u64, sign_extend: bool) -> ValueRef {
535 llvm::LLVMConstInt(t.to_ref(), u, sign_extend as Bool)
539 pub fn C_floating(s: &str, t: Type) -> ValueRef {
541 s.with_c_str(|buf| llvm::LLVMConstRealOfString(t.to_ref(), buf))
545 pub fn C_nil(ccx: &CrateContext) -> ValueRef {
546 C_struct(ccx, &[], false)
549 pub fn C_bool(ccx: &CrateContext, val: bool) -> ValueRef {
550 C_integral(Type::i1(ccx), val as u64, false)
553 pub fn C_i32(ccx: &CrateContext, i: i32) -> ValueRef {
554 C_integral(Type::i32(ccx), i as u64, true)
557 pub fn C_i64(ccx: &CrateContext, i: i64) -> ValueRef {
558 C_integral(Type::i64(ccx), i as u64, true)
561 pub fn C_u64(ccx: &CrateContext, i: u64) -> ValueRef {
562 C_integral(Type::i64(ccx), i, false)
565 pub fn C_int<I: AsI64>(ccx: &CrateContext, i: I) -> ValueRef {
568 match machine::llbitsize_of_real(ccx, ccx.int_type()) {
569 32 => assert!(v < (1<<31) && v >= -(1<<31)),
571 n => panic!("unsupported target size: {}", n)
574 C_integral(ccx.int_type(), v as u64, true)
577 pub fn C_uint<I: AsU64>(ccx: &CrateContext, i: I) -> ValueRef {
580 match machine::llbitsize_of_real(ccx, ccx.int_type()) {
581 32 => assert!(v < (1<<32)),
583 n => panic!("unsupported target size: {}", n)
586 C_integral(ccx.int_type(), v, false)
589 pub trait AsI64 { fn as_i64(self) -> i64; }
590 pub trait AsU64 { fn as_u64(self) -> u64; }
592 // FIXME: remove the intptr conversions, because they
593 // are host-architecture-dependent
594 impl AsI64 for i64 { fn as_i64(self) -> i64 { self as i64 }}
595 impl AsI64 for i32 { fn as_i64(self) -> i64 { self as i64 }}
596 impl AsI64 for int { fn as_i64(self) -> i64 { self as i64 }}
598 impl AsU64 for u64 { fn as_u64(self) -> u64 { self as u64 }}
599 impl AsU64 for u32 { fn as_u64(self) -> u64 { self as u64 }}
600 impl AsU64 for uint { fn as_u64(self) -> u64 { self as u64 }}
602 pub fn C_u8(ccx: &CrateContext, i: uint) -> ValueRef {
603 C_integral(Type::i8(ccx), i as u64, false)
607 // This is a 'c-like' raw string, which differs from
608 // our boxed-and-length-annotated strings.
609 pub fn C_cstr(cx: &CrateContext, s: InternedString, null_terminated: bool) -> ValueRef {
611 match cx.const_cstr_cache().borrow().get(&s) {
612 Some(&llval) => return llval,
616 let sc = llvm::LLVMConstStringInContext(cx.llcx(),
617 s.get().as_ptr() as *const c_char,
618 s.get().len() as c_uint,
619 !null_terminated as Bool);
621 let gsym = token::gensym("str");
622 let g = format!("str{}", gsym.uint()).with_c_str(|buf| {
623 llvm::LLVMAddGlobal(cx.llmod(), val_ty(sc).to_ref(), buf)
625 llvm::LLVMSetInitializer(g, sc);
626 llvm::LLVMSetGlobalConstant(g, True);
627 llvm::SetLinkage(g, llvm::InternalLinkage);
629 cx.const_cstr_cache().borrow_mut().insert(s, g);
634 // NB: Do not use `do_spill_noroot` to make this into a constant string, or
635 // you will be kicked off fast isel. See issue #4352 for an example of this.
636 pub fn C_str_slice(cx: &CrateContext, s: InternedString) -> ValueRef {
638 let len = s.get().len();
639 let cs = llvm::LLVMConstPointerCast(C_cstr(cx, s, false),
640 Type::i8p(cx).to_ref());
641 C_named_struct(cx.tn().find_type("str_slice").unwrap(), &[cs, C_uint(cx, len)])
645 pub fn C_binary_slice(cx: &CrateContext, data: &[u8]) -> ValueRef {
647 let len = data.len();
648 let lldata = C_bytes(cx, data);
650 let gsym = token::gensym("binary");
651 let g = format!("binary{}", gsym.uint()).with_c_str(|buf| {
652 llvm::LLVMAddGlobal(cx.llmod(), val_ty(lldata).to_ref(), buf)
654 llvm::LLVMSetInitializer(g, lldata);
655 llvm::LLVMSetGlobalConstant(g, True);
656 llvm::SetLinkage(g, llvm::InternalLinkage);
658 let cs = llvm::LLVMConstPointerCast(g, Type::i8p(cx).to_ref());
659 C_struct(cx, &[cs, C_uint(cx, len)], false)
663 pub fn C_struct(cx: &CrateContext, elts: &[ValueRef], packed: bool) -> ValueRef {
664 C_struct_in_context(cx.llcx(), elts, packed)
667 pub fn C_struct_in_context(llcx: ContextRef, elts: &[ValueRef], packed: bool) -> ValueRef {
669 llvm::LLVMConstStructInContext(llcx,
670 elts.as_ptr(), elts.len() as c_uint,
675 pub fn C_named_struct(t: Type, elts: &[ValueRef]) -> ValueRef {
677 llvm::LLVMConstNamedStruct(t.to_ref(), elts.as_ptr(), elts.len() as c_uint)
681 pub fn C_array(ty: Type, elts: &[ValueRef]) -> ValueRef {
683 return llvm::LLVMConstArray(ty.to_ref(), elts.as_ptr(), elts.len() as c_uint);
687 pub fn C_bytes(cx: &CrateContext, bytes: &[u8]) -> ValueRef {
688 C_bytes_in_context(cx.llcx(), bytes)
691 pub fn C_bytes_in_context(llcx: ContextRef, bytes: &[u8]) -> ValueRef {
693 let ptr = bytes.as_ptr() as *const c_char;
694 return llvm::LLVMConstStringInContext(llcx, ptr, bytes.len() as c_uint, True);
698 pub fn const_get_elt(cx: &CrateContext, v: ValueRef, us: &[c_uint])
701 let r = llvm::LLVMConstExtractValue(v, us.as_ptr(), us.len() as c_uint);
703 debug!("const_get_elt(v={}, us={}, r={})",
704 cx.tn().val_to_string(v), us, cx.tn().val_to_string(r));
710 pub fn is_const(v: ValueRef) -> bool {
712 llvm::LLVMIsConstant(v) == True
716 pub fn const_to_int(v: ValueRef) -> i64 {
718 llvm::LLVMConstIntGetSExtValue(v)
722 pub fn const_to_uint(v: ValueRef) -> u64 {
724 llvm::LLVMConstIntGetZExtValue(v)
728 pub fn is_undef(val: ValueRef) -> bool {
730 llvm::LLVMIsUndef(val) != False
734 pub fn is_null(val: ValueRef) -> bool {
736 llvm::LLVMIsNull(val) != False
740 pub fn monomorphize_type<'blk, 'tcx>(bcx: &BlockS<'blk, 'tcx>, t: Ty<'tcx>) -> Ty<'tcx> {
741 t.subst(bcx.tcx(), bcx.fcx.param_substs)
744 pub fn node_id_type<'blk, 'tcx>(bcx: &BlockS<'blk, 'tcx>, id: ast::NodeId) -> Ty<'tcx> {
746 let t = ty::node_id_to_type(tcx, id);
747 monomorphize_type(bcx, t)
750 pub fn expr_ty<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, ex: &ast::Expr) -> Ty<'tcx> {
751 node_id_type(bcx, ex.id)
754 pub fn expr_ty_adjusted<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, ex: &ast::Expr) -> Ty<'tcx> {
755 monomorphize_type(bcx, ty::expr_ty_adjusted(bcx.tcx(), ex))
758 /// Attempts to resolve an obligation. The result is a shallow vtable resolution -- meaning that we
759 /// do not (necessarily) resolve all nested obligations on the impl. Note that type check should
760 /// guarantee to us that all nested obligations *could be* resolved if we wanted to.
761 pub fn fulfill_obligation<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
763 trait_ref: Rc<ty::TraitRef<'tcx>>)
764 -> traits::Vtable<'tcx, ()>
768 // Remove any references to regions; this helps improve caching.
769 let trait_ref = ty_fold::erase_regions(tcx, trait_ref);
771 // First check the cache.
772 match ccx.trait_cache().borrow().get(&trait_ref) {
774 info!("Cache hit: {}", trait_ref.repr(ccx.tcx()));
775 return (*vtable).clone();
780 debug!("trans fulfill_obligation: trait_ref={}", trait_ref.repr(ccx.tcx()));
782 ty::populate_implementations_for_trait_if_necessary(tcx, trait_ref.def_id);
783 let infcx = infer::new_infer_ctxt(tcx);
785 // Parameter environment is used to give details about type parameters,
786 // but since we are in trans, everything is fully monomorphized.
787 let param_env = ty::empty_parameter_environment();
789 // Do the initial selection for the obligation. This yields the
790 // shallow result we are looking for -- that is, what specific impl.
791 let mut selcx = traits::SelectionContext::new(&infcx, ¶m_env, tcx);
792 let obligation = traits::Obligation::misc(span, trait_ref.clone());
793 let selection = match selcx.select(&obligation) {
794 Ok(Some(selection)) => selection,
796 // Ambiguity can happen when monomorphizing during trans
797 // expands to some humongo type that never occurred
798 // statically -- this humongo type can then overflow,
799 // leading to an ambiguous result. So report this as an
800 // overflow bug, since I believe this is the only case
801 // where ambiguity can result.
802 debug!("Encountered ambiguity selecting `{}` during trans, \
803 presuming due to overflow",
804 trait_ref.repr(tcx));
805 ccx.sess().span_fatal(
807 "reached the recursion limit during monomorphization");
812 format!("Encountered error `{}` selecting `{}` during trans",
814 trait_ref.repr(tcx)).as_slice())
818 // Currently, we use a fulfillment context to completely resolve
819 // all nested obligations. This is because they can inform the
820 // inference of the impl's type parameters. However, in principle,
821 // we only need to do this until the impl's type parameters are
822 // fully bound. It could be a slight optimization to stop
824 let mut fulfill_cx = traits::FulfillmentContext::new();
825 let vtable = selection.map_move_nested(|obligation| {
826 fulfill_cx.register_obligation(tcx, obligation);
828 match fulfill_cx.select_all_or_error(&infcx, ¶m_env, tcx) {
831 if errors.iter().all(|e| e.is_overflow()) {
832 // See Ok(None) case above.
833 ccx.sess().span_fatal(
835 "reached the recursion limit during monomorphization");
839 format!("Encountered errors `{}` fulfilling `{}` during trans",
841 trait_ref.repr(tcx)).as_slice());
846 // Use skolemize to simultaneously replace all type variables with
847 // their bindings and replace all regions with 'static. This is
848 // sort of overkill because we do not expect there to be any
849 // unbound type variables, hence no skolemized types should ever
851 let vtable = vtable.fold_with(&mut infcx.skolemizer());
853 info!("Cache miss: {}", trait_ref.repr(ccx.tcx()));
854 ccx.trait_cache().borrow_mut().insert(trait_ref,
860 // Key used to lookup values supplied for type parameters in an expr.
861 #[deriving(PartialEq, Show)]
862 pub enum ExprOrMethodCall {
863 // Type parameters for a path like `None::<int>`
866 // Type parameters for a method call like `a.foo::<int>()`
867 MethodCall(ty::MethodCall)
870 pub fn node_id_substs<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
871 node: ExprOrMethodCall)
872 -> subst::Substs<'tcx>
876 let substs = match node {
878 ty::node_id_item_substs(tcx, id).substs
880 MethodCall(method_call) => {
881 (*tcx.method_map.borrow())[method_call].substs.clone()
885 if substs.types.any(|t| ty::type_needs_infer(*t)) {
887 format!("type parameters for node {} include inference types: \
890 substs.repr(bcx.tcx())).as_slice());
893 let substs = substs.erase_regions();
894 substs.subst(tcx, bcx.fcx.param_substs)
897 pub fn langcall(bcx: Block,
902 match bcx.tcx().lang_items.require(li) {
905 let msg = format!("{} {}", msg, s);
907 Some(span) => bcx.tcx().sess.span_fatal(span, msg.as_slice()),
908 None => bcx.tcx().sess.fatal(msg.as_slice()),