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use std::iter;
use rustc_index::bit_set::BitSet;
use rustc_index::IndexVec;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::mir::{traversal, UnwindTerminateReason};
use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, TyAndLayout};
use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
use rustc_middle::{bug, mir, span_bug};
use rustc_target::abi::call::{FnAbi, PassMode};
use tracing::{debug, instrument};
use crate::base;
use crate::traits::*;
mod analyze;
mod block;
pub mod constant;
pub mod coverageinfo;
pub mod debuginfo;
mod intrinsic;
mod locals;
pub mod operand;
pub mod place;
mod rvalue;
mod statement;
use self::debuginfo::{FunctionDebugContext, PerLocalVarDebugInfo};
use self::operand::{OperandRef, OperandValue};
use self::place::PlaceRef;
// Used for tracking the state of generated basic blocks.
enum CachedLlbb<T> {
/// Nothing created yet.
None,
/// Has been created.
Some(T),
/// Nothing created yet, and nothing should be.
Skip,
}
/// Master context for codegenning from MIR.
pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
instance: Instance<'tcx>,
mir: &'tcx mir::Body<'tcx>,
debug_context: Option<FunctionDebugContext<'tcx, Bx::DIScope, Bx::DILocation>>,
llfn: Bx::Function,
cx: &'a Bx::CodegenCx,
fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
/// When unwinding is initiated, we have to store this personality
/// value somewhere so that we can load it and re-use it in the
/// resume instruction. The personality is (afaik) some kind of
/// value used for C++ unwinding, which must filter by type: we
/// don't really care about it very much. Anyway, this value
/// contains an alloca into which the personality is stored and
/// then later loaded when generating the DIVERGE_BLOCK.
personality_slot: Option<PlaceRef<'tcx, Bx::Value>>,
/// A backend `BasicBlock` for each MIR `BasicBlock`, created lazily
/// as-needed (e.g. RPO reaching it or another block branching to it).
// FIXME(eddyb) rename `llbbs` and other `ll`-prefixed things to use a
// more backend-agnostic prefix such as `cg` (i.e. this would be `cgbbs`).
cached_llbbs: IndexVec<mir::BasicBlock, CachedLlbb<Bx::BasicBlock>>,
/// The funclet status of each basic block
cleanup_kinds: Option<IndexVec<mir::BasicBlock, analyze::CleanupKind>>,
/// When targeting MSVC, this stores the cleanup info for each funclet BB.
/// This is initialized at the same time as the `landing_pads` entry for the
/// funclets' head block, i.e. when needed by an unwind / `cleanup_ret` edge.
funclets: IndexVec<mir::BasicBlock, Option<Bx::Funclet>>,
/// This stores the cached landing/cleanup pad block for a given BB.
// FIXME(eddyb) rename this to `eh_pads`.
landing_pads: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
/// Cached unreachable block
unreachable_block: Option<Bx::BasicBlock>,
/// Cached terminate upon unwinding block and its reason
terminate_block: Option<(Bx::BasicBlock, UnwindTerminateReason)>,
/// The location where each MIR arg/var/tmp/ret is stored. This is
/// usually an `PlaceRef` representing an alloca, but not always:
/// sometimes we can skip the alloca and just store the value
/// directly using an `OperandRef`, which makes for tighter LLVM
/// IR. The conditions for using an `OperandRef` are as follows:
///
/// - the type of the local must be judged "immediate" by `is_llvm_immediate`
/// - the operand must never be referenced indirectly
/// - we should not take its address using the `&` operator
/// - nor should it appear in a place path like `tmp.a`
/// - the operand must be defined by an rvalue that can generate immediate
/// values
///
/// Avoiding allocs can also be important for certain intrinsics,
/// notably `expect`.
locals: locals::Locals<'tcx, Bx::Value>,
/// All `VarDebugInfo` from the MIR body, partitioned by `Local`.
/// This is `None` if no variable debuginfo/names are needed.
per_local_var_debug_info:
Option<IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, Bx::DIVariable>>>>,
/// Caller location propagated if this function has `#[track_caller]`.
caller_location: Option<OperandRef<'tcx, Bx::Value>>,
}
impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
pub fn monomorphize<T>(&self, value: T) -> T
where
T: Copy + TypeFoldable<TyCtxt<'tcx>>,
{
debug!("monomorphize: self.instance={:?}", self.instance);
self.instance.instantiate_mir_and_normalize_erasing_regions(
self.cx.tcx(),
ty::ParamEnv::reveal_all(),
ty::EarlyBinder::bind(value),
)
}
}
enum LocalRef<'tcx, V> {
Place(PlaceRef<'tcx, V>),
/// `UnsizedPlace(p)`: `p` itself is a thin pointer (indirect place).
/// `*p` is the fat pointer that references the actual unsized place.
/// Every time it is initialized, we have to reallocate the place
/// and update the fat pointer. That's the reason why it is indirect.
UnsizedPlace(PlaceRef<'tcx, V>),
/// The backend [`OperandValue`] has already been generated.
Operand(OperandRef<'tcx, V>),
/// Will be a `Self::Operand` once we get to its definition.
PendingOperand,
}
impl<'tcx, V: CodegenObject> LocalRef<'tcx, V> {
fn new_operand(layout: TyAndLayout<'tcx>) -> LocalRef<'tcx, V> {
if layout.is_zst() {
// Zero-size temporaries aren't always initialized, which
// doesn't matter because they don't contain data, but
// we need something sufficiently aligned in the operand.
LocalRef::Operand(OperandRef::zero_sized(layout))
} else {
LocalRef::PendingOperand
}
}
}
///////////////////////////////////////////////////////////////////////////
#[instrument(level = "debug", skip(cx))]
pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
cx: &'a Bx::CodegenCx,
instance: Instance<'tcx>,
) {
assert!(!instance.args.has_infer());
let llfn = cx.get_fn(instance);
let mir = cx.tcx().instance_mir(instance.def);
let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
debug!("fn_abi: {:?}", fn_abi);
let debug_context = cx.create_function_debug_context(instance, fn_abi, llfn, mir);
let start_llbb = Bx::append_block(cx, llfn, "start");
let mut start_bx = Bx::build(cx, start_llbb);
if mir.basic_blocks.iter().any(|bb| {
bb.is_cleanup || matches!(bb.terminator().unwind(), Some(mir::UnwindAction::Terminate(_)))
}) {
start_bx.set_personality_fn(cx.eh_personality());
}
let cleanup_kinds =
base::wants_new_eh_instructions(cx.tcx().sess).then(|| analyze::cleanup_kinds(mir));
let cached_llbbs: IndexVec<mir::BasicBlock, CachedLlbb<Bx::BasicBlock>> =
mir.basic_blocks
.indices()
.map(|bb| {
if bb == mir::START_BLOCK { CachedLlbb::Some(start_llbb) } else { CachedLlbb::None }
})
.collect();
let mut fx = FunctionCx {
instance,
mir,
llfn,
fn_abi,
cx,
personality_slot: None,
cached_llbbs,
unreachable_block: None,
terminate_block: None,
cleanup_kinds,
landing_pads: IndexVec::from_elem(None, &mir.basic_blocks),
funclets: IndexVec::from_fn_n(|_| None, mir.basic_blocks.len()),
locals: locals::Locals::empty(),
debug_context,
per_local_var_debug_info: None,
caller_location: None,
};
// It may seem like we should iterate over `required_consts` to ensure they all successfully
// evaluate; however, the `MirUsedCollector` already did that during the collection phase of
// monomorphization, and if there is an error during collection then codegen never starts -- so
// we don't have to do it again.
fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info(&mut start_bx);
let memory_locals = analyze::non_ssa_locals(&fx);
// Allocate variable and temp allocas
let local_values = {
let args = arg_local_refs(&mut start_bx, &mut fx, &memory_locals);
let mut allocate_local = |local| {
let decl = &mir.local_decls[local];
let layout = start_bx.layout_of(fx.monomorphize(decl.ty));
assert!(!layout.ty.has_erasable_regions());
if local == mir::RETURN_PLACE {
match fx.fn_abi.ret.mode {
PassMode::Indirect { .. } => {
debug!("alloc: {:?} (return place) -> place", local);
let llretptr = start_bx.get_param(0);
return LocalRef::Place(PlaceRef::new_sized(llretptr, layout));
}
PassMode::Cast { ref cast, .. } => {
debug!("alloc: {:?} (return place) -> place", local);
let size = cast.size(&start_bx);
return LocalRef::Place(PlaceRef::alloca_size(&mut start_bx, size, layout));
}
_ => {}
};
}
if memory_locals.contains(local) {
debug!("alloc: {:?} -> place", local);
if layout.is_unsized() {
LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut start_bx, layout))
} else {
LocalRef::Place(PlaceRef::alloca(&mut start_bx, layout))
}
} else {
debug!("alloc: {:?} -> operand", local);
LocalRef::new_operand(layout)
}
};
let retptr = allocate_local(mir::RETURN_PLACE);
iter::once(retptr)
.chain(args.into_iter())
.chain(mir.vars_and_temps_iter().map(allocate_local))
.collect()
};
fx.initialize_locals(local_values);
// Apply debuginfo to the newly allocated locals.
fx.debug_introduce_locals(&mut start_bx);
// If the backend supports coverage, and coverage is enabled for this function,
// do any necessary start-of-function codegen (e.g. locals for MC/DC bitmaps).
start_bx.init_coverage(instance);
// The builders will be created separately for each basic block at `codegen_block`.
// So drop the builder of `start_llbb` to avoid having two at the same time.
drop(start_bx);
let reachable_blocks = traversal::mono_reachable_as_bitset(mir, cx.tcx(), instance);
// Codegen the body of each block using reverse postorder
for (bb, _) in traversal::reverse_postorder(mir) {
if reachable_blocks.contains(bb) {
fx.codegen_block(bb);
} else {
// We want to skip this block, because it's not reachable. But we still create
// the block so terminators in other blocks can reference it.
fx.codegen_block_as_unreachable(bb);
}
}
}
/// Produces, for each argument, a `Value` pointing at the
/// argument's value. As arguments are places, these are always
/// indirect.
fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
bx: &mut Bx,
fx: &mut FunctionCx<'a, 'tcx, Bx>,
memory_locals: &BitSet<mir::Local>,
) -> Vec<LocalRef<'tcx, Bx::Value>> {
let mir = fx.mir;
let mut idx = 0;
let mut llarg_idx = fx.fn_abi.ret.is_indirect() as usize;
let mut num_untupled = None;
let codegen_fn_attrs = bx.tcx().codegen_fn_attrs(fx.instance.def_id());
let naked = codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED);
if naked {
return vec![];
}
let args = mir
.args_iter()
.enumerate()
.map(|(arg_index, local)| {
let arg_decl = &mir.local_decls[local];
let arg_ty = fx.monomorphize(arg_decl.ty);
if Some(local) == mir.spread_arg {
// This argument (e.g., the last argument in the "rust-call" ABI)
// is a tuple that was spread at the ABI level and now we have
// to reconstruct it into a tuple local variable, from multiple
// individual LLVM function arguments.
let ty::Tuple(tupled_arg_tys) = arg_ty.kind() else {
bug!("spread argument isn't a tuple?!");
};
let layout = bx.layout_of(arg_ty);
// FIXME: support unsized params in "rust-call" ABI
if layout.is_unsized() {
span_bug!(
arg_decl.source_info.span,
"\"rust-call\" ABI does not support unsized params",
);
}
let place = PlaceRef::alloca(bx, layout);
for i in 0..tupled_arg_tys.len() {
let arg = &fx.fn_abi.args[idx];
idx += 1;
if let PassMode::Cast { pad_i32: true, .. } = arg.mode {
llarg_idx += 1;
}
let pr_field = place.project_field(bx, i);
bx.store_fn_arg(arg, &mut llarg_idx, pr_field);
}
assert_eq!(
None,
num_untupled.replace(tupled_arg_tys.len()),
"Replaced existing num_tupled"
);
return LocalRef::Place(place);
}
if fx.fn_abi.c_variadic && arg_index == fx.fn_abi.args.len() {
let va_list = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
bx.va_start(va_list.val.llval);
return LocalRef::Place(va_list);
}
let arg = &fx.fn_abi.args[idx];
idx += 1;
if let PassMode::Cast { pad_i32: true, .. } = arg.mode {
llarg_idx += 1;
}
if !memory_locals.contains(local) {
// We don't have to cast or keep the argument in the alloca.
// FIXME(eddyb): We should figure out how to use llvm.dbg.value instead
// of putting everything in allocas just so we can use llvm.dbg.declare.
let local = |op| LocalRef::Operand(op);
match arg.mode {
PassMode::Ignore => {
return local(OperandRef::zero_sized(arg.layout));
}
PassMode::Direct(_) => {
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
return local(OperandRef::from_immediate_or_packed_pair(
bx, llarg, arg.layout,
));
}
PassMode::Pair(..) => {
let (a, b) = (bx.get_param(llarg_idx), bx.get_param(llarg_idx + 1));
llarg_idx += 2;
return local(OperandRef {
val: OperandValue::Pair(a, b),
layout: arg.layout,
});
}
_ => {}
}
}
match arg.mode {
// Sized indirect arguments
PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
// Don't copy an indirect argument to an alloca, the caller already put it
// in a temporary alloca and gave it up.
// FIXME: lifetimes
if let Some(pointee_align) = attrs.pointee_align
&& pointee_align < arg.layout.align.abi
{
// ...unless the argument is underaligned, then we need to copy it to
// a higher-aligned alloca.
let tmp = PlaceRef::alloca(bx, arg.layout);
bx.store_fn_arg(arg, &mut llarg_idx, tmp);
LocalRef::Place(tmp)
} else {
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
}
}
// Unsized indirect qrguments
PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
// As the storage for the indirect argument lives during
// the whole function call, we just copy the fat pointer.
let llarg = bx.get_param(llarg_idx);
llarg_idx += 1;
let llextra = bx.get_param(llarg_idx);
llarg_idx += 1;
let indirect_operand = OperandValue::Pair(llarg, llextra);
let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
indirect_operand.store(bx, tmp);
LocalRef::UnsizedPlace(tmp)
}
_ => {
let tmp = PlaceRef::alloca(bx, arg.layout);
bx.store_fn_arg(arg, &mut llarg_idx, tmp);
LocalRef::Place(tmp)
}
}
})
.collect::<Vec<_>>();
if fx.instance.def.requires_caller_location(bx.tcx()) {
let mir_args = if let Some(num_untupled) = num_untupled {
// Subtract off the tupled argument that gets 'expanded'
args.len() - 1 + num_untupled
} else {
args.len()
};
assert_eq!(
fx.fn_abi.args.len(),
mir_args + 1,
"#[track_caller] instance {:?} must have 1 more argument in their ABI than in their MIR",
fx.instance
);
let arg = fx.fn_abi.args.last().unwrap();
match arg.mode {
PassMode::Direct(_) => (),
_ => bug!("caller location must be PassMode::Direct, found {:?}", arg.mode),
}
fx.caller_location = Some(OperandRef {
val: OperandValue::Immediate(bx.get_param(llarg_idx)),
layout: arg.layout,
});
}
args
}