1 use rustc::ty::{self, Ty, TypeFoldable, Instance};
2 use rustc::ty::layout::{TyLayout, HasTyCtxt, FnAbiExt};
3 use rustc::mir::{self, Body, ReadOnlyBodyCache};
4 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::ReadOnlyBodyCache<'a, '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<&'a mir::VarDebugInfo<'tcx>>>>,
82 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
83 pub fn monomorphize<T>(&self, value: &T) -> T
84 where T: TypeFoldable<'tcx>
86 self.cx.tcx().subst_and_normalize_erasing_regions(
88 ty::ParamEnv::reveal_all(),
94 enum LocalRef<'tcx, V> {
95 Place(PlaceRef<'tcx, V>),
96 /// `UnsizedPlace(p)`: `p` itself is a thin pointer (indirect place).
97 /// `*p` is the fat pointer that references the actual unsized place.
98 /// Every time it is initialized, we have to reallocate the place
99 /// and update the fat pointer. That's the reason why it is indirect.
100 UnsizedPlace(PlaceRef<'tcx, V>),
101 Operand(Option<OperandRef<'tcx, V>>),
104 impl<'a, 'tcx, V: CodegenObject> LocalRef<'tcx, V> {
105 fn new_operand<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
107 layout: TyLayout<'tcx>,
108 ) -> LocalRef<'tcx, V> {
110 // Zero-size temporaries aren't always initialized, which
111 // doesn't matter because they don't contain data, but
112 // we need something in the operand.
113 LocalRef::Operand(Some(OperandRef::new_zst(bx, layout)))
115 LocalRef::Operand(None)
120 ///////////////////////////////////////////////////////////////////////////
122 pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
123 cx: &'a Bx::CodegenCx,
125 mir: ReadOnlyBodyCache<'a, 'tcx>,
126 instance: Instance<'tcx>,
127 sig: ty::FnSig<'tcx>,
129 assert!(!instance.substs.needs_infer());
131 let fn_abi = FnAbi::new(cx, sig, &[]);
132 debug!("fn_abi: {:?}", fn_abi);
135 cx.create_function_debug_context(instance, sig, llfn, &mir);
137 let mut bx = Bx::new_block(cx, llfn, "start");
139 if mir.basic_blocks().iter().any(|bb| bb.is_cleanup) {
140 bx.set_personality_fn(cx.eh_personality());
145 let cleanup_kinds = analyze::cleanup_kinds(&mir);
146 // Allocate a `Block` for every basic block, except
147 // the start block, if nothing loops back to it.
148 let reentrant_start_block = !mir.predecessors_for(mir::START_BLOCK).is_empty();
149 let block_bxs: IndexVec<mir::BasicBlock, Bx::BasicBlock> =
150 mir.basic_blocks().indices().map(|bb| {
151 if bb == mir::START_BLOCK && !reentrant_start_block {
154 bx.build_sibling_block(&format!("{:?}", bb)).llbb()
158 let (landing_pads, funclets) = create_funclets(&mir, &mut bx, &cleanup_kinds, &block_bxs);
159 let mir_body: &Body<'_> = mir.body();
160 let mut fx = FunctionCx {
166 personality_slot: None,
168 unreachable_block: None,
172 locals: IndexVec::new(),
174 per_local_var_debug_info: debuginfo::per_local_var_debug_info(cx.tcx(), mir_body),
177 let memory_locals = analyze::non_ssa_locals(&fx);
179 // Allocate variable and temp allocas
181 let args = arg_local_refs(&mut bx, &fx, &memory_locals);
183 let mut allocate_local = |local| {
184 let decl = &mir_body.local_decls[local];
185 let layout = bx.layout_of(fx.monomorphize(&decl.ty));
186 assert!(!layout.ty.has_erasable_regions());
188 if local == mir::RETURN_PLACE && fx.fn_abi.ret.is_indirect() {
189 debug!("alloc: {:?} (return place) -> place", local);
190 let llretptr = bx.get_param(0);
191 return LocalRef::Place(PlaceRef::new_sized(llretptr, layout));
194 if memory_locals.contains(local) {
195 debug!("alloc: {:?} -> place", local);
196 if layout.is_unsized() {
197 LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut bx, layout))
199 LocalRef::Place(PlaceRef::alloca(&mut bx, layout))
202 debug!("alloc: {:?} -> operand", local);
203 LocalRef::new_operand(&mut bx, layout)
207 let retptr = allocate_local(mir::RETURN_PLACE);
209 .chain(args.into_iter())
210 .chain(mir_body.vars_and_temps_iter().map(allocate_local))
214 // Apply debuginfo to the newly allocated locals.
215 fx.debug_introduce_locals(&mut bx);
217 // Branch to the START block, if it's not the entry block.
218 if reentrant_start_block {
219 bx.br(fx.blocks[mir::START_BLOCK]);
222 // Up until here, IR instructions for this function have explicitly not been annotated with
223 // source code location, so we don't step into call setup code. From here on, source location
224 // emitting should be enabled.
225 if let Some(debug_context) = &mut fx.debug_context {
226 debug_context.source_locations_enabled = true;
229 let rpo = traversal::reverse_postorder(&mir_body);
230 let mut visited = BitSet::new_empty(mir_body.basic_blocks().len());
232 // Codegen the body of each block using reverse postorder
234 visited.insert(bb.index());
235 fx.codegen_block(bb);
238 // Remove blocks that haven't been visited, or have no
240 for bb in mir_body.basic_blocks().indices() {
242 if !visited.contains(bb.index()) {
243 debug!("codegen_mir: block {:?} was not visited", bb);
245 bx.delete_basic_block(fx.blocks[bb]);
251 fn create_funclets<'a, 'b, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
254 cleanup_kinds: &IndexVec<mir::BasicBlock, CleanupKind>,
255 block_bxs: &IndexVec<mir::BasicBlock, Bx::BasicBlock>,
257 IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
258 IndexVec<mir::BasicBlock, Option<Bx::Funclet>>,
260 block_bxs.iter_enumerated().zip(cleanup_kinds).map(|((bb, &llbb), cleanup_kind)| {
261 match *cleanup_kind {
262 CleanupKind::Funclet if base::wants_msvc_seh(bx.sess()) => {}
263 _ => return (None, None)
268 match mir[bb].terminator.as_ref().map(|t| &t.kind) {
269 // This is a basic block that we're aborting the program for,
270 // notably in an `extern` function. These basic blocks are inserted
271 // so that we assert that `extern` functions do indeed not panic,
272 // and if they do we abort the process.
274 // On MSVC these are tricky though (where we're doing funclets). If
275 // we were to do a cleanuppad (like below) the normal functions like
276 // `longjmp` would trigger the abort logic, terminating the
277 // program. Instead we insert the equivalent of `catch(...)` for C++
278 // which magically doesn't trigger when `longjmp` files over this
281 // Lots more discussion can be found on #48251 but this codegen is
282 // modeled after clang's for:
289 Some(&mir::TerminatorKind::Abort) => {
290 let mut cs_bx = bx.build_sibling_block(&format!("cs_funclet{:?}", bb));
291 let mut cp_bx = bx.build_sibling_block(&format!("cp_funclet{:?}", bb));
292 ret_llbb = cs_bx.llbb();
294 let cs = cs_bx.catch_switch(None, None, 1);
295 cs_bx.add_handler(cs, cp_bx.llbb());
297 // The "null" here is actually a RTTI type descriptor for the
298 // C++ personality function, but `catch (...)` has no type so
299 // it's null. The 64 here is actually a bitfield which
300 // represents that this is a catch-all block.
301 let null = bx.const_null(bx.type_i8p());
302 let sixty_four = bx.const_i32(64);
303 funclet = cp_bx.catch_pad(cs, &[null, sixty_four, null]);
307 let mut cleanup_bx = bx.build_sibling_block(&format!("funclet_{:?}", bb));
308 ret_llbb = cleanup_bx.llbb();
309 funclet = cleanup_bx.cleanup_pad(None, &[]);
314 (Some(ret_llbb), Some(funclet))
318 /// Produces, for each argument, a `Value` pointing at the
319 /// argument's value. As arguments are places, these are always
321 fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
323 fx: &FunctionCx<'a, 'tcx, Bx>,
324 memory_locals: &BitSet<mir::Local>,
325 ) -> Vec<LocalRef<'tcx, Bx::Value>> {
328 let mut llarg_idx = fx.fn_abi.ret.is_indirect() as usize;
330 mir.args_iter().enumerate().map(|(arg_index, local)| {
331 let arg_decl = &mir.local_decls[local];
333 if Some(local) == mir.spread_arg {
334 // This argument (e.g., the last argument in the "rust-call" ABI)
335 // is a tuple that was spread at the ABI level and now we have
336 // to reconstruct it into a tuple local variable, from multiple
337 // individual LLVM function arguments.
339 let arg_ty = fx.monomorphize(&arg_decl.ty);
340 let tupled_arg_tys = match arg_ty.kind {
341 ty::Tuple(ref tys) => tys,
342 _ => bug!("spread argument isn't a tuple?!")
345 let place = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
346 for i in 0..tupled_arg_tys.len() {
347 let arg = &fx.fn_abi.args[idx];
349 if arg.pad.is_some() {
352 let pr_field = place.project_field(bx, i);
353 bx.store_fn_arg(arg, &mut llarg_idx, pr_field);
356 return LocalRef::Place(place);
359 if fx.fn_abi.c_variadic && arg_index == fx.fn_abi.args.len() {
360 let arg_ty = fx.monomorphize(&arg_decl.ty);
362 let va_list = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
363 bx.va_start(va_list.llval);
365 return LocalRef::Place(va_list);
368 let arg = &fx.fn_abi.args[idx];
370 if arg.pad.is_some() {
374 if !memory_locals.contains(local) {
375 // We don't have to cast or keep the argument in the alloca.
376 // FIXME(eddyb): We should figure out how to use llvm.dbg.value instead
377 // of putting everything in allocas just so we can use llvm.dbg.declare.
378 let local = |op| LocalRef::Operand(Some(op));
380 PassMode::Ignore => {
381 return local(OperandRef::new_zst(bx, arg.layout));
383 PassMode::Direct(_) => {
384 let llarg = bx.get_param(llarg_idx);
387 OperandRef::from_immediate_or_packed_pair(bx, llarg, arg.layout));
389 PassMode::Pair(..) => {
390 let (a, b) = (bx.get_param(llarg_idx), bx.get_param(llarg_idx + 1));
393 return local(OperandRef {
394 val: OperandValue::Pair(a, b),
402 if arg.is_sized_indirect() {
403 // Don't copy an indirect argument to an alloca, the caller
404 // already put it in a temporary alloca and gave it up.
406 let llarg = bx.get_param(llarg_idx);
408 LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
409 } else if arg.is_unsized_indirect() {
410 // As the storage for the indirect argument lives during
411 // the whole function call, we just copy the fat pointer.
412 let llarg = bx.get_param(llarg_idx);
414 let llextra = bx.get_param(llarg_idx);
416 let indirect_operand = OperandValue::Pair(llarg, llextra);
418 let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
419 indirect_operand.store(bx, tmp);
420 LocalRef::UnsizedPlace(tmp)
422 let tmp = PlaceRef::alloca(bx, arg.layout);
423 bx.store_fn_arg(arg, &mut llarg_idx, tmp);