4 use rustc::ty::layout::{FnAbiExt, HasTyCtxt, TyLayout};
5 use rustc::ty::{self, Instance, Ty, TypeFoldable};
6 use rustc_target::abi::call::{FnAbi, PassMode};
10 use rustc_index::bit_set::BitSet;
11 use rustc_index::vec::IndexVec;
13 use self::analyze::CleanupKind;
14 use self::debuginfo::FunctionDebugContext;
15 use self::place::PlaceRef;
16 use rustc::mir::traversal;
18 use self::operand::{OperandRef, OperandValue};
20 /// Master context for codegenning from MIR.
21 pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
22 instance: Instance<'tcx>,
24 mir: mir::ReadOnlyBodyAndCache<'tcx, 'tcx>,
26 debug_context: Option<FunctionDebugContext<Bx::DIScope>>,
30 cx: &'a Bx::CodegenCx,
32 fn_abi: FnAbi<'tcx, Ty<'tcx>>,
34 /// When unwinding is initiated, we have to store this personality
35 /// value somewhere so that we can load it and re-use it in the
36 /// resume instruction. The personality is (afaik) some kind of
37 /// value used for C++ unwinding, which must filter by type: we
38 /// don't really care about it very much. Anyway, this value
39 /// contains an alloca into which the personality is stored and
40 /// then later loaded when generating the DIVERGE_BLOCK.
41 personality_slot: Option<PlaceRef<'tcx, Bx::Value>>,
43 /// A `Block` for each MIR `BasicBlock`
44 blocks: IndexVec<mir::BasicBlock, Bx::BasicBlock>,
46 /// The funclet status of each basic block
47 cleanup_kinds: IndexVec<mir::BasicBlock, analyze::CleanupKind>,
49 /// When targeting MSVC, this stores the cleanup info for each funclet
50 /// BB. This is initialized as we compute the funclets' head block in RPO.
51 funclets: IndexVec<mir::BasicBlock, Option<Bx::Funclet>>,
53 /// This stores the landing-pad block for a given BB, computed lazily on GNU
54 /// and eagerly on MSVC.
55 landing_pads: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
57 /// Cached unreachable block
58 unreachable_block: Option<Bx::BasicBlock>,
60 /// The location where each MIR arg/var/tmp/ret is stored. This is
61 /// usually an `PlaceRef` representing an alloca, but not always:
62 /// sometimes we can skip the alloca and just store the value
63 /// directly using an `OperandRef`, which makes for tighter LLVM
64 /// IR. The conditions for using an `OperandRef` are as follows:
66 /// - the type of the local must be judged "immediate" by `is_llvm_immediate`
67 /// - the operand must never be referenced indirectly
68 /// - we should not take its address using the `&` operator
69 /// - nor should it appear in a place path like `tmp.a`
70 /// - the operand must be defined by an rvalue that can generate immediate
73 /// Avoiding allocs can also be important for certain intrinsics,
75 locals: IndexVec<mir::Local, LocalRef<'tcx, Bx::Value>>,
77 /// All `VarDebuginfo` from the MIR body, partitioned by `Local`.
78 /// This is `None` if no variable debuginfo/names are needed.
79 per_local_var_debug_info: Option<IndexVec<mir::Local, Vec<&'tcx mir::VarDebugInfo<'tcx>>>>,
81 /// Caller location propagated if this function has `#[track_caller]`.
82 caller_location: Option<OperandRef<'tcx, Bx::Value>>,
85 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
86 pub fn monomorphize<T>(&self, value: &T) -> T
88 T: TypeFoldable<'tcx>,
90 self.cx.tcx().subst_and_normalize_erasing_regions(
92 ty::ParamEnv::reveal_all(),
98 enum LocalRef<'tcx, V> {
99 Place(PlaceRef<'tcx, V>),
100 /// `UnsizedPlace(p)`: `p` itself is a thin pointer (indirect place).
101 /// `*p` is the fat pointer that references the actual unsized place.
102 /// Every time it is initialized, we have to reallocate the place
103 /// and update the fat pointer. That's the reason why it is indirect.
104 UnsizedPlace(PlaceRef<'tcx, V>),
105 Operand(Option<OperandRef<'tcx, V>>),
108 impl<'a, 'tcx, V: CodegenObject> LocalRef<'tcx, V> {
109 fn new_operand<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
111 layout: TyLayout<'tcx>,
112 ) -> LocalRef<'tcx, V> {
114 // Zero-size temporaries aren't always initialized, which
115 // doesn't matter because they don't contain data, but
116 // we need something in the operand.
117 LocalRef::Operand(Some(OperandRef::new_zst(bx, layout)))
119 LocalRef::Operand(None)
124 ///////////////////////////////////////////////////////////////////////////
126 pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
127 cx: &'a Bx::CodegenCx,
128 instance: Instance<'tcx>,
130 assert!(!instance.substs.needs_infer());
132 let llfn = cx.get_fn(instance);
134 let mir = cx.tcx().instance_mir(instance.def);
136 let fn_abi = FnAbi::of_instance(cx, instance, &[]);
137 debug!("fn_abi: {:?}", fn_abi);
139 let debug_context = cx.create_function_debug_context(instance, &fn_abi, llfn, &mir);
141 let mut bx = Bx::new_block(cx, llfn, "start");
143 if mir.basic_blocks().iter().any(|bb| bb.is_cleanup) {
144 bx.set_personality_fn(cx.eh_personality());
149 let cleanup_kinds = analyze::cleanup_kinds(&mir);
150 // Allocate a `Block` for every basic block, except
151 // the start block, if nothing loops back to it.
152 let reentrant_start_block = !mir.predecessors_for(mir::START_BLOCK).is_empty();
153 let block_bxs: IndexVec<mir::BasicBlock, Bx::BasicBlock> = mir
157 if bb == mir::START_BLOCK && !reentrant_start_block {
160 bx.build_sibling_block(&format!("{:?}", bb)).llbb()
165 let (landing_pads, funclets) = create_funclets(&mir, &mut bx, &cleanup_kinds, &block_bxs);
166 let mir_body: &mir::Body<'_> = *mir;
167 let mut fx = FunctionCx {
173 personality_slot: None,
175 unreachable_block: None,
179 locals: IndexVec::new(),
181 per_local_var_debug_info: debuginfo::per_local_var_debug_info(cx.tcx(), mir_body),
182 caller_location: None,
185 let memory_locals = analyze::non_ssa_locals(&fx);
187 // Allocate variable and temp allocas
189 let args = arg_local_refs(&mut bx, &mut fx, &memory_locals);
191 let mut allocate_local = |local| {
192 let decl = &mir_body.local_decls[local];
193 let layout = bx.layout_of(fx.monomorphize(&decl.ty));
194 assert!(!layout.ty.has_erasable_regions());
196 if local == mir::RETURN_PLACE && fx.fn_abi.ret.is_indirect() {
197 debug!("alloc: {:?} (return place) -> place", local);
198 let llretptr = bx.get_param(0);
199 return LocalRef::Place(PlaceRef::new_sized(llretptr, layout));
202 if memory_locals.contains(local) {
203 debug!("alloc: {:?} -> place", local);
204 if layout.is_unsized() {
205 LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut bx, layout))
207 LocalRef::Place(PlaceRef::alloca(&mut bx, layout))
210 debug!("alloc: {:?} -> operand", local);
211 LocalRef::new_operand(&mut bx, layout)
215 let retptr = allocate_local(mir::RETURN_PLACE);
217 .chain(args.into_iter())
218 .chain(mir_body.vars_and_temps_iter().map(allocate_local))
222 // Apply debuginfo to the newly allocated locals.
223 fx.debug_introduce_locals(&mut bx);
225 // Branch to the START block, if it's not the entry block.
226 if reentrant_start_block {
227 bx.br(fx.blocks[mir::START_BLOCK]);
230 // Up until here, IR instructions for this function have explicitly not been annotated with
231 // source code location, so we don't step into call setup code. From here on, source location
232 // emitting should be enabled.
233 if let Some(debug_context) = &mut fx.debug_context {
234 debug_context.source_locations_enabled = true;
237 let rpo = traversal::reverse_postorder(&mir_body);
238 let mut visited = BitSet::new_empty(mir_body.basic_blocks().len());
240 // Codegen the body of each block using reverse postorder
242 visited.insert(bb.index());
243 fx.codegen_block(bb);
246 // Remove blocks that haven't been visited, or have no
248 for bb in mir_body.basic_blocks().indices() {
250 if !visited.contains(bb.index()) {
251 debug!("codegen_mir: block {:?} was not visited", bb);
253 bx.delete_basic_block(fx.blocks[bb]);
259 fn create_funclets<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
260 mir: &'tcx mir::Body<'tcx>,
262 cleanup_kinds: &IndexVec<mir::BasicBlock, CleanupKind>,
263 block_bxs: &IndexVec<mir::BasicBlock, Bx::BasicBlock>,
265 IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
266 IndexVec<mir::BasicBlock, Option<Bx::Funclet>>,
271 .map(|((bb, &llbb), cleanup_kind)| {
272 match *cleanup_kind {
273 CleanupKind::Funclet if base::wants_msvc_seh(bx.sess()) => {}
274 _ => return (None, None),
279 match mir[bb].terminator.as_ref().map(|t| &t.kind) {
280 // This is a basic block that we're aborting the program for,
281 // notably in an `extern` function. These basic blocks are inserted
282 // so that we assert that `extern` functions do indeed not panic,
283 // and if they do we abort the process.
285 // On MSVC these are tricky though (where we're doing funclets). If
286 // we were to do a cleanuppad (like below) the normal functions like
287 // `longjmp` would trigger the abort logic, terminating the
288 // program. Instead we insert the equivalent of `catch(...)` for C++
289 // which magically doesn't trigger when `longjmp` files over this
292 // Lots more discussion can be found on #48251 but this codegen is
293 // modeled after clang's for:
300 Some(&mir::TerminatorKind::Abort) => {
301 let mut cs_bx = bx.build_sibling_block(&format!("cs_funclet{:?}", bb));
302 let mut cp_bx = bx.build_sibling_block(&format!("cp_funclet{:?}", bb));
303 ret_llbb = cs_bx.llbb();
305 let cs = cs_bx.catch_switch(None, None, 1);
306 cs_bx.add_handler(cs, cp_bx.llbb());
308 // The "null" here is actually a RTTI type descriptor for the
309 // C++ personality function, but `catch (...)` has no type so
310 // it's null. The 64 here is actually a bitfield which
311 // represents that this is a catch-all block.
312 let null = bx.const_null(bx.type_i8p());
313 let sixty_four = bx.const_i32(64);
314 funclet = cp_bx.catch_pad(cs, &[null, sixty_four, null]);
318 let mut cleanup_bx = bx.build_sibling_block(&format!("funclet_{:?}", bb));
319 ret_llbb = cleanup_bx.llbb();
320 funclet = cleanup_bx.cleanup_pad(None, &[]);
325 (Some(ret_llbb), Some(funclet))
330 /// Produces, for each argument, a `Value` pointing at the
331 /// argument's value. As arguments are places, these are always
333 fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
335 fx: &mut FunctionCx<'a, 'tcx, Bx>,
336 memory_locals: &BitSet<mir::Local>,
337 ) -> Vec<LocalRef<'tcx, Bx::Value>> {
340 let mut llarg_idx = fx.fn_abi.ret.is_indirect() as usize;
345 .map(|(arg_index, local)| {
346 let arg_decl = &mir.local_decls[local];
348 if Some(local) == mir.spread_arg {
349 // This argument (e.g., the last argument in the "rust-call" ABI)
350 // is a tuple that was spread at the ABI level and now we have
351 // to reconstruct it into a tuple local variable, from multiple
352 // individual LLVM function arguments.
354 let arg_ty = fx.monomorphize(&arg_decl.ty);
355 let tupled_arg_tys = match arg_ty.kind {
356 ty::Tuple(ref tys) => tys,
357 _ => bug!("spread argument isn't a tuple?!"),
360 let place = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
361 for i in 0..tupled_arg_tys.len() {
362 let arg = &fx.fn_abi.args[idx];
364 if arg.pad.is_some() {
367 let pr_field = place.project_field(bx, i);
368 bx.store_fn_arg(arg, &mut llarg_idx, pr_field);
371 return LocalRef::Place(place);
374 if fx.fn_abi.c_variadic && arg_index == fx.fn_abi.args.len() {
375 let arg_ty = fx.monomorphize(&arg_decl.ty);
377 let va_list = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
378 bx.va_start(va_list.llval);
380 return LocalRef::Place(va_list);
383 let arg = &fx.fn_abi.args[idx];
385 if arg.pad.is_some() {
389 if !memory_locals.contains(local) {
390 // We don't have to cast or keep the argument in the alloca.
391 // FIXME(eddyb): We should figure out how to use llvm.dbg.value instead
392 // of putting everything in allocas just so we can use llvm.dbg.declare.
393 let local = |op| LocalRef::Operand(Some(op));
395 PassMode::Ignore => {
396 return local(OperandRef::new_zst(bx, arg.layout));
398 PassMode::Direct(_) => {
399 let llarg = bx.get_param(llarg_idx);
401 return local(OperandRef::from_immediate_or_packed_pair(
402 bx, llarg, arg.layout,
405 PassMode::Pair(..) => {
406 let (a, b) = (bx.get_param(llarg_idx), bx.get_param(llarg_idx + 1));
409 return local(OperandRef {
410 val: OperandValue::Pair(a, b),
418 if arg.is_sized_indirect() {
419 // Don't copy an indirect argument to an alloca, the caller
420 // already put it in a temporary alloca and gave it up.
422 let llarg = bx.get_param(llarg_idx);
424 LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
425 } else if arg.is_unsized_indirect() {
426 // As the storage for the indirect argument lives during
427 // the whole function call, we just copy the fat pointer.
428 let llarg = bx.get_param(llarg_idx);
430 let llextra = bx.get_param(llarg_idx);
432 let indirect_operand = OperandValue::Pair(llarg, llextra);
434 let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
435 indirect_operand.store(bx, tmp);
436 LocalRef::UnsizedPlace(tmp)
438 let tmp = PlaceRef::alloca(bx, arg.layout);
439 bx.store_fn_arg(arg, &mut llarg_idx, tmp);
443 .collect::<Vec<_>>();
445 if fx.instance.def.requires_caller_location(bx.tcx()) {
447 fx.fn_abi.args.len(),
449 "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR",
452 let arg = fx.fn_abi.args.last().unwrap();
454 PassMode::Direct(_) => (),
455 _ => bug!("caller location must be PassMode::Direct, found {:?}", arg.mode),
458 fx.caller_location = Some(OperandRef {
459 val: OperandValue::Immediate(bx.get_param(llarg_idx)),