9cba14b95b
the behavior of the type system not only depends on the current assumptions, but also the currentnphase of the compiler. This is mostly necessary as we need to decide whether and how to reveal opaque types. We track this via the `TypingMode`.
521 lines
20 KiB
Rust
521 lines
20 KiB
Rust
use std::iter;
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use rustc_index::IndexVec;
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use rustc_index::bit_set::BitSet;
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use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
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use rustc_middle::mir::{UnwindTerminateReason, traversal};
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use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, HasTypingEnv, TyAndLayout};
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use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
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use rustc_middle::{bug, mir, span_bug};
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use rustc_target::callconv::{FnAbi, PassMode};
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use tracing::{debug, instrument};
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use crate::base;
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use crate::traits::*;
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mod analyze;
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mod block;
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mod constant;
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mod coverageinfo;
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pub mod debuginfo;
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mod intrinsic;
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mod locals;
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pub mod operand;
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pub mod place;
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mod rvalue;
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mod statement;
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use self::debuginfo::{FunctionDebugContext, PerLocalVarDebugInfo};
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use self::operand::{OperandRef, OperandValue};
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use self::place::PlaceRef;
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// Used for tracking the state of generated basic blocks.
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enum CachedLlbb<T> {
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/// Nothing created yet.
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None,
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/// Has been created.
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Some(T),
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/// Nothing created yet, and nothing should be.
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Skip,
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}
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type PerLocalVarDebugInfoIndexVec<'tcx, V> =
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IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, V>>>;
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/// Master context for codegenning from MIR.
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pub struct FunctionCx<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
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instance: Instance<'tcx>,
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mir: &'tcx mir::Body<'tcx>,
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debug_context: Option<FunctionDebugContext<'tcx, Bx::DIScope, Bx::DILocation>>,
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llfn: Bx::Function,
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cx: &'a Bx::CodegenCx,
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fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
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/// When unwinding is initiated, we have to store this personality
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/// value somewhere so that we can load it and re-use it in the
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/// resume instruction. The personality is (afaik) some kind of
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/// value used for C++ unwinding, which must filter by type: we
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/// don't really care about it very much. Anyway, this value
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/// contains an alloca into which the personality is stored and
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/// then later loaded when generating the DIVERGE_BLOCK.
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personality_slot: Option<PlaceRef<'tcx, Bx::Value>>,
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/// A backend `BasicBlock` for each MIR `BasicBlock`, created lazily
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/// as-needed (e.g. RPO reaching it or another block branching to it).
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// FIXME(eddyb) rename `llbbs` and other `ll`-prefixed things to use a
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// more backend-agnostic prefix such as `cg` (i.e. this would be `cgbbs`).
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cached_llbbs: IndexVec<mir::BasicBlock, CachedLlbb<Bx::BasicBlock>>,
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/// The funclet status of each basic block
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cleanup_kinds: Option<IndexVec<mir::BasicBlock, analyze::CleanupKind>>,
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/// When targeting MSVC, this stores the cleanup info for each funclet BB.
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/// This is initialized at the same time as the `landing_pads` entry for the
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/// funclets' head block, i.e. when needed by an unwind / `cleanup_ret` edge.
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funclets: IndexVec<mir::BasicBlock, Option<Bx::Funclet>>,
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/// This stores the cached landing/cleanup pad block for a given BB.
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// FIXME(eddyb) rename this to `eh_pads`.
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landing_pads: IndexVec<mir::BasicBlock, Option<Bx::BasicBlock>>,
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/// Cached unreachable block
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unreachable_block: Option<Bx::BasicBlock>,
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/// Cached terminate upon unwinding block and its reason
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terminate_block: Option<(Bx::BasicBlock, UnwindTerminateReason)>,
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/// A bool flag for each basic block indicating whether it is a cold block.
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/// A cold block is a block that is unlikely to be executed at runtime.
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cold_blocks: IndexVec<mir::BasicBlock, bool>,
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/// The location where each MIR arg/var/tmp/ret is stored. This is
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/// usually an `PlaceRef` representing an alloca, but not always:
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/// sometimes we can skip the alloca and just store the value
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/// directly using an `OperandRef`, which makes for tighter LLVM
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/// IR. The conditions for using an `OperandRef` are as follows:
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///
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/// - the type of the local must be judged "immediate" by `is_llvm_immediate`
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/// - the operand must never be referenced indirectly
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/// - we should not take its address using the `&` operator
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/// - nor should it appear in a place path like `tmp.a`
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/// - the operand must be defined by an rvalue that can generate immediate
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/// values
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///
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/// Avoiding allocs can also be important for certain intrinsics,
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/// notably `expect`.
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locals: locals::Locals<'tcx, Bx::Value>,
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/// All `VarDebugInfo` from the MIR body, partitioned by `Local`.
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/// This is `None` if no variable debuginfo/names are needed.
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per_local_var_debug_info: Option<PerLocalVarDebugInfoIndexVec<'tcx, Bx::DIVariable>>,
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/// Caller location propagated if this function has `#[track_caller]`.
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caller_location: Option<OperandRef<'tcx, Bx::Value>>,
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}
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impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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pub fn monomorphize<T>(&self, value: T) -> T
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where
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T: Copy + TypeFoldable<TyCtxt<'tcx>>,
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{
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debug!("monomorphize: self.instance={:?}", self.instance);
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self.instance.instantiate_mir_and_normalize_erasing_regions(
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self.cx.tcx(),
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self.cx.typing_env(),
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ty::EarlyBinder::bind(value),
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)
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}
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}
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enum LocalRef<'tcx, V> {
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Place(PlaceRef<'tcx, V>),
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/// `UnsizedPlace(p)`: `p` itself is a thin pointer (indirect place).
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/// `*p` is the wide pointer that references the actual unsized place.
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/// Every time it is initialized, we have to reallocate the place
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/// and update the wide pointer. That's the reason why it is indirect.
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UnsizedPlace(PlaceRef<'tcx, V>),
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/// The backend [`OperandValue`] has already been generated.
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Operand(OperandRef<'tcx, V>),
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/// Will be a `Self::Operand` once we get to its definition.
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PendingOperand,
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}
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impl<'tcx, V: CodegenObject> LocalRef<'tcx, V> {
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fn new_operand(layout: TyAndLayout<'tcx>) -> LocalRef<'tcx, V> {
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if layout.is_zst() {
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// Zero-size temporaries aren't always initialized, which
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// doesn't matter because they don't contain data, but
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// we need something sufficiently aligned in the operand.
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LocalRef::Operand(OperandRef::zero_sized(layout))
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} else {
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LocalRef::PendingOperand
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}
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}
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}
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///////////////////////////////////////////////////////////////////////////
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#[instrument(level = "debug", skip(cx))]
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pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
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cx: &'a Bx::CodegenCx,
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instance: Instance<'tcx>,
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) {
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assert!(!instance.args.has_infer());
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let llfn = cx.get_fn(instance);
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let mir = cx.tcx().instance_mir(instance.def);
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let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
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debug!("fn_abi: {:?}", fn_abi);
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let debug_context = cx.create_function_debug_context(instance, fn_abi, llfn, mir);
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let start_llbb = Bx::append_block(cx, llfn, "start");
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let mut start_bx = Bx::build(cx, start_llbb);
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if mir.basic_blocks.iter().any(|bb| {
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bb.is_cleanup || matches!(bb.terminator().unwind(), Some(mir::UnwindAction::Terminate(_)))
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}) {
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start_bx.set_personality_fn(cx.eh_personality());
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}
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let cleanup_kinds =
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base::wants_new_eh_instructions(cx.tcx().sess).then(|| analyze::cleanup_kinds(mir));
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let cached_llbbs: IndexVec<mir::BasicBlock, CachedLlbb<Bx::BasicBlock>> =
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mir.basic_blocks
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.indices()
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.map(|bb| {
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if bb == mir::START_BLOCK { CachedLlbb::Some(start_llbb) } else { CachedLlbb::None }
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})
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.collect();
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let mut fx = FunctionCx {
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instance,
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mir,
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llfn,
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fn_abi,
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cx,
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personality_slot: None,
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cached_llbbs,
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unreachable_block: None,
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terminate_block: None,
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cleanup_kinds,
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landing_pads: IndexVec::from_elem(None, &mir.basic_blocks),
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funclets: IndexVec::from_fn_n(|_| None, mir.basic_blocks.len()),
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cold_blocks: find_cold_blocks(cx.tcx(), mir),
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locals: locals::Locals::empty(),
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debug_context,
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per_local_var_debug_info: None,
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caller_location: None,
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};
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// It may seem like we should iterate over `required_consts` to ensure they all successfully
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// evaluate; however, the `MirUsedCollector` already did that during the collection phase of
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// monomorphization, and if there is an error during collection then codegen never starts -- so
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// we don't have to do it again.
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let (per_local_var_debug_info, consts_debug_info) =
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fx.compute_per_local_var_debug_info(&mut start_bx).unzip();
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fx.per_local_var_debug_info = per_local_var_debug_info;
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let traversal_order = traversal::mono_reachable_reverse_postorder(mir, cx.tcx(), instance);
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let memory_locals = analyze::non_ssa_locals(&fx, &traversal_order);
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// Allocate variable and temp allocas
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let local_values = {
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let args = arg_local_refs(&mut start_bx, &mut fx, &memory_locals);
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let mut allocate_local = |local| {
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let decl = &mir.local_decls[local];
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let layout = start_bx.layout_of(fx.monomorphize(decl.ty));
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assert!(!layout.ty.has_erasable_regions());
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if local == mir::RETURN_PLACE {
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match fx.fn_abi.ret.mode {
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PassMode::Indirect { .. } => {
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debug!("alloc: {:?} (return place) -> place", local);
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let llretptr = start_bx.get_param(0);
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return LocalRef::Place(PlaceRef::new_sized(llretptr, layout));
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}
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PassMode::Cast { ref cast, .. } => {
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debug!("alloc: {:?} (return place) -> place", local);
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let size = cast.size(&start_bx);
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return LocalRef::Place(PlaceRef::alloca_size(&mut start_bx, size, layout));
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}
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_ => {}
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};
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}
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if memory_locals.contains(local) {
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debug!("alloc: {:?} -> place", local);
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if layout.is_unsized() {
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LocalRef::UnsizedPlace(PlaceRef::alloca_unsized_indirect(&mut start_bx, layout))
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} else {
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LocalRef::Place(PlaceRef::alloca(&mut start_bx, layout))
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}
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} else {
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debug!("alloc: {:?} -> operand", local);
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LocalRef::new_operand(layout)
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}
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};
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let retptr = allocate_local(mir::RETURN_PLACE);
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iter::once(retptr)
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.chain(args.into_iter())
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.chain(mir.vars_and_temps_iter().map(allocate_local))
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.collect()
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};
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fx.initialize_locals(local_values);
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// Apply debuginfo to the newly allocated locals.
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fx.debug_introduce_locals(&mut start_bx, consts_debug_info.unwrap_or_default());
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// If the backend supports coverage, and coverage is enabled for this function,
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// do any necessary start-of-function codegen (e.g. locals for MC/DC bitmaps).
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start_bx.init_coverage(instance);
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// The builders will be created separately for each basic block at `codegen_block`.
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// So drop the builder of `start_llbb` to avoid having two at the same time.
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drop(start_bx);
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let mut unreached_blocks = BitSet::new_filled(mir.basic_blocks.len());
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// Codegen the body of each reachable block using our reverse postorder list.
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for bb in traversal_order {
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fx.codegen_block(bb);
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unreached_blocks.remove(bb);
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}
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// FIXME: These empty unreachable blocks are *mostly* a waste. They are occasionally
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// targets for a SwitchInt terminator, but the reimplementation of the mono-reachable
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// simplification in SwitchInt lowering sometimes misses cases that
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// mono_reachable_reverse_postorder manages to figure out.
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// The solution is to do something like post-mono GVN. But for now we have this hack.
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for bb in unreached_blocks.iter() {
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fx.codegen_block_as_unreachable(bb);
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}
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}
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/// Produces, for each argument, a `Value` pointing at the
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/// argument's value. As arguments are places, these are always
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/// indirect.
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fn arg_local_refs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
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bx: &mut Bx,
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fx: &mut FunctionCx<'a, 'tcx, Bx>,
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memory_locals: &BitSet<mir::Local>,
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) -> Vec<LocalRef<'tcx, Bx::Value>> {
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let mir = fx.mir;
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let mut idx = 0;
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let mut llarg_idx = fx.fn_abi.ret.is_indirect() as usize;
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let mut num_untupled = None;
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let codegen_fn_attrs = bx.tcx().codegen_fn_attrs(fx.instance.def_id());
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let naked = codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED);
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if naked {
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return vec![];
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}
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let args = mir
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.args_iter()
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.enumerate()
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.map(|(arg_index, local)| {
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let arg_decl = &mir.local_decls[local];
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let arg_ty = fx.monomorphize(arg_decl.ty);
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if Some(local) == mir.spread_arg {
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// This argument (e.g., the last argument in the "rust-call" ABI)
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// is a tuple that was spread at the ABI level and now we have
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// to reconstruct it into a tuple local variable, from multiple
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// individual LLVM function arguments.
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let ty::Tuple(tupled_arg_tys) = arg_ty.kind() else {
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bug!("spread argument isn't a tuple?!");
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};
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let layout = bx.layout_of(arg_ty);
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// FIXME: support unsized params in "rust-call" ABI
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if layout.is_unsized() {
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span_bug!(
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arg_decl.source_info.span,
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"\"rust-call\" ABI does not support unsized params",
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);
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}
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let place = PlaceRef::alloca(bx, layout);
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for i in 0..tupled_arg_tys.len() {
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let arg = &fx.fn_abi.args[idx];
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idx += 1;
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if let PassMode::Cast { pad_i32: true, .. } = arg.mode {
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llarg_idx += 1;
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}
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let pr_field = place.project_field(bx, i);
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bx.store_fn_arg(arg, &mut llarg_idx, pr_field);
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}
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assert_eq!(
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None,
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num_untupled.replace(tupled_arg_tys.len()),
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"Replaced existing num_tupled"
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);
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return LocalRef::Place(place);
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}
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if fx.fn_abi.c_variadic && arg_index == fx.fn_abi.args.len() {
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let va_list = PlaceRef::alloca(bx, bx.layout_of(arg_ty));
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bx.va_start(va_list.val.llval);
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return LocalRef::Place(va_list);
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}
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let arg = &fx.fn_abi.args[idx];
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idx += 1;
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if let PassMode::Cast { pad_i32: true, .. } = arg.mode {
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llarg_idx += 1;
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}
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if !memory_locals.contains(local) {
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// We don't have to cast or keep the argument in the alloca.
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// FIXME(eddyb): We should figure out how to use llvm.dbg.value instead
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// of putting everything in allocas just so we can use llvm.dbg.declare.
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let local = |op| LocalRef::Operand(op);
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match arg.mode {
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PassMode::Ignore => {
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return local(OperandRef::zero_sized(arg.layout));
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}
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PassMode::Direct(_) => {
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let llarg = bx.get_param(llarg_idx);
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llarg_idx += 1;
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return local(OperandRef::from_immediate_or_packed_pair(
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bx, llarg, arg.layout,
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));
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}
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PassMode::Pair(..) => {
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let (a, b) = (bx.get_param(llarg_idx), bx.get_param(llarg_idx + 1));
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llarg_idx += 2;
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return local(OperandRef {
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val: OperandValue::Pair(a, b),
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layout: arg.layout,
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});
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}
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_ => {}
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}
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}
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match arg.mode {
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// Sized indirect arguments
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PassMode::Indirect { attrs, meta_attrs: None, on_stack: _ } => {
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// Don't copy an indirect argument to an alloca, the caller already put it
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// in a temporary alloca and gave it up.
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// FIXME: lifetimes
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if let Some(pointee_align) = attrs.pointee_align
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&& pointee_align < arg.layout.align.abi
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{
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// ...unless the argument is underaligned, then we need to copy it to
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// a higher-aligned alloca.
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let tmp = PlaceRef::alloca(bx, arg.layout);
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bx.store_fn_arg(arg, &mut llarg_idx, tmp);
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LocalRef::Place(tmp)
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} else {
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let llarg = bx.get_param(llarg_idx);
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llarg_idx += 1;
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LocalRef::Place(PlaceRef::new_sized(llarg, arg.layout))
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}
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}
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// Unsized indirect qrguments
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PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
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// As the storage for the indirect argument lives during
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// the whole function call, we just copy the wide pointer.
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let llarg = bx.get_param(llarg_idx);
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llarg_idx += 1;
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let llextra = bx.get_param(llarg_idx);
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llarg_idx += 1;
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let indirect_operand = OperandValue::Pair(llarg, llextra);
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let tmp = PlaceRef::alloca_unsized_indirect(bx, arg.layout);
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indirect_operand.store(bx, tmp);
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LocalRef::UnsizedPlace(tmp)
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}
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_ => {
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let tmp = PlaceRef::alloca(bx, arg.layout);
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bx.store_fn_arg(arg, &mut llarg_idx, tmp);
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LocalRef::Place(tmp)
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}
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}
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})
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.collect::<Vec<_>>();
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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
|
|
}
|
|
|
|
fn find_cold_blocks<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
mir: &mir::Body<'tcx>,
|
|
) -> IndexVec<mir::BasicBlock, bool> {
|
|
let local_decls = &mir.local_decls;
|
|
|
|
let mut cold_blocks: IndexVec<mir::BasicBlock, bool> =
|
|
IndexVec::from_elem(false, &mir.basic_blocks);
|
|
|
|
// Traverse all basic blocks from end of the function to the start.
|
|
for (bb, bb_data) in traversal::postorder(mir) {
|
|
let terminator = bb_data.terminator();
|
|
|
|
// If a BB ends with a call to a cold function, mark it as cold.
|
|
if let mir::TerminatorKind::Call { ref func, .. } = terminator.kind
|
|
&& let ty::FnDef(def_id, ..) = *func.ty(local_decls, tcx).kind()
|
|
&& let attrs = tcx.codegen_fn_attrs(def_id)
|
|
&& attrs.flags.contains(CodegenFnAttrFlags::COLD)
|
|
{
|
|
cold_blocks[bb] = true;
|
|
continue;
|
|
}
|
|
|
|
// If all successors of a BB are cold and there's at least one of them, mark this BB as cold
|
|
let mut succ = terminator.successors();
|
|
if let Some(first) = succ.next()
|
|
&& cold_blocks[first]
|
|
&& succ.all(|s| cold_blocks[s])
|
|
{
|
|
cold_blocks[bb] = true;
|
|
}
|
|
}
|
|
|
|
cold_blocks
|
|
}
|