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Diffstat (limited to 'compiler/rustc_middle/src/mir/terminator.rs')
| -rw-r--r-- | compiler/rustc_middle/src/mir/terminator.rs | 448 |
1 files changed, 448 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs new file mode 100644 index 000000000..9ccf5aea6 --- /dev/null +++ b/compiler/rustc_middle/src/mir/terminator.rs @@ -0,0 +1,448 @@ +use crate::mir; +use crate::mir::interpret::Scalar; +use crate::ty::{self, Ty, TyCtxt}; +use smallvec::{smallvec, SmallVec}; + +use super::{BasicBlock, InlineAsmOperand, Operand, SourceInfo, TerminatorKind}; +use rustc_ast::InlineAsmTemplatePiece; +pub use rustc_ast::Mutability; +use rustc_macros::HashStable; +use std::borrow::Cow; +use std::fmt::{self, Debug, Formatter, Write}; +use std::iter; +use std::slice; + +pub use super::query::*; + +#[derive(Debug, Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, PartialOrd)] +pub struct SwitchTargets { + /// Possible values. The locations to branch to in each case + /// are found in the corresponding indices from the `targets` vector. + values: SmallVec<[u128; 1]>, + + /// Possible branch sites. The last element of this vector is used + /// for the otherwise branch, so targets.len() == values.len() + 1 + /// should hold. + // + // This invariant is quite non-obvious and also could be improved. + // One way to make this invariant is to have something like this instead: + // + // branches: Vec<(ConstInt, BasicBlock)>, + // otherwise: Option<BasicBlock> // exhaustive if None + // + // However we’ve decided to keep this as-is until we figure a case + // where some other approach seems to be strictly better than other. + targets: SmallVec<[BasicBlock; 2]>, +} + +impl SwitchTargets { + /// Creates switch targets from an iterator of values and target blocks. + /// + /// The iterator may be empty, in which case the `SwitchInt` instruction is equivalent to + /// `goto otherwise;`. + pub fn new(targets: impl Iterator<Item = (u128, BasicBlock)>, otherwise: BasicBlock) -> Self { + let (values, mut targets): (SmallVec<_>, SmallVec<_>) = targets.unzip(); + targets.push(otherwise); + Self { values, targets } + } + + /// Builds a switch targets definition that jumps to `then` if the tested value equals `value`, + /// and to `else_` if not. + pub fn static_if(value: u128, then: BasicBlock, else_: BasicBlock) -> Self { + Self { values: smallvec![value], targets: smallvec![then, else_] } + } + + /// Returns the fallback target that is jumped to when none of the values match the operand. + pub fn otherwise(&self) -> BasicBlock { + *self.targets.last().unwrap() + } + + /// Returns an iterator over the switch targets. + /// + /// The iterator will yield tuples containing the value and corresponding target to jump to, not + /// including the `otherwise` fallback target. + /// + /// Note that this may yield 0 elements. Only the `otherwise` branch is mandatory. + pub fn iter(&self) -> SwitchTargetsIter<'_> { + SwitchTargetsIter { inner: iter::zip(&self.values, &self.targets) } + } + + /// Returns a slice with all possible jump targets (including the fallback target). + pub fn all_targets(&self) -> &[BasicBlock] { + &self.targets + } + + pub fn all_targets_mut(&mut self) -> &mut [BasicBlock] { + &mut self.targets + } + + /// Finds the `BasicBlock` to which this `SwitchInt` will branch given the + /// specific value. This cannot fail, as it'll return the `otherwise` + /// branch if there's not a specific match for the value. + pub fn target_for_value(&self, value: u128) -> BasicBlock { + self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise()) + } +} + +pub struct SwitchTargetsIter<'a> { + inner: iter::Zip<slice::Iter<'a, u128>, slice::Iter<'a, BasicBlock>>, +} + +impl<'a> Iterator for SwitchTargetsIter<'a> { + type Item = (u128, BasicBlock); + + fn next(&mut self) -> Option<Self::Item> { + self.inner.next().map(|(val, bb)| (*val, *bb)) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.inner.size_hint() + } +} + +impl<'a> ExactSizeIterator for SwitchTargetsIter<'a> {} + +#[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)] +pub struct Terminator<'tcx> { + pub source_info: SourceInfo, + pub kind: TerminatorKind<'tcx>, +} + +pub type Successors<'a> = impl Iterator<Item = BasicBlock> + 'a; +pub type SuccessorsMut<'a> = + iter::Chain<std::option::IntoIter<&'a mut BasicBlock>, slice::IterMut<'a, BasicBlock>>; + +impl<'tcx> Terminator<'tcx> { + pub fn successors(&self) -> Successors<'_> { + self.kind.successors() + } + + pub fn successors_mut(&mut self) -> SuccessorsMut<'_> { + self.kind.successors_mut() + } + + pub fn unwind(&self) -> Option<&Option<BasicBlock>> { + self.kind.unwind() + } + + pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> { + self.kind.unwind_mut() + } +} + +impl<'tcx> TerminatorKind<'tcx> { + pub fn if_( + tcx: TyCtxt<'tcx>, + cond: Operand<'tcx>, + t: BasicBlock, + f: BasicBlock, + ) -> TerminatorKind<'tcx> { + TerminatorKind::SwitchInt { + discr: cond, + switch_ty: tcx.types.bool, + targets: SwitchTargets::static_if(0, f, t), + } + } + + pub fn successors(&self) -> Successors<'_> { + use self::TerminatorKind::*; + match *self { + Resume + | Abort + | GeneratorDrop + | Return + | Unreachable + | Call { target: None, cleanup: None, .. } + | InlineAsm { destination: None, cleanup: None, .. } => { + None.into_iter().chain((&[]).into_iter().copied()) + } + Goto { target: t } + | Call { target: None, cleanup: Some(t), .. } + | Call { target: Some(t), cleanup: None, .. } + | Yield { resume: t, drop: None, .. } + | DropAndReplace { target: t, unwind: None, .. } + | Drop { target: t, unwind: None, .. } + | Assert { target: t, cleanup: None, .. } + | FalseUnwind { real_target: t, unwind: None } + | InlineAsm { destination: Some(t), cleanup: None, .. } + | InlineAsm { destination: None, cleanup: Some(t), .. } => { + Some(t).into_iter().chain((&[]).into_iter().copied()) + } + Call { target: Some(t), cleanup: Some(ref u), .. } + | Yield { resume: t, drop: Some(ref u), .. } + | DropAndReplace { target: t, unwind: Some(ref u), .. } + | Drop { target: t, unwind: Some(ref u), .. } + | Assert { target: t, cleanup: Some(ref u), .. } + | FalseUnwind { real_target: t, unwind: Some(ref u) } + | InlineAsm { destination: Some(t), cleanup: Some(ref u), .. } => { + Some(t).into_iter().chain(slice::from_ref(u).into_iter().copied()) + } + SwitchInt { ref targets, .. } => { + None.into_iter().chain(targets.targets.iter().copied()) + } + FalseEdge { real_target, ref imaginary_target } => Some(real_target) + .into_iter() + .chain(slice::from_ref(imaginary_target).into_iter().copied()), + } + } + + pub fn successors_mut(&mut self) -> SuccessorsMut<'_> { + use self::TerminatorKind::*; + match *self { + Resume + | Abort + | GeneratorDrop + | Return + | Unreachable + | Call { target: None, cleanup: None, .. } + | InlineAsm { destination: None, cleanup: None, .. } => None.into_iter().chain(&mut []), + Goto { target: ref mut t } + | Call { target: None, cleanup: Some(ref mut t), .. } + | Call { target: Some(ref mut t), cleanup: None, .. } + | Yield { resume: ref mut t, drop: None, .. } + | DropAndReplace { target: ref mut t, unwind: None, .. } + | Drop { target: ref mut t, unwind: None, .. } + | Assert { target: ref mut t, cleanup: None, .. } + | FalseUnwind { real_target: ref mut t, unwind: None } + | InlineAsm { destination: Some(ref mut t), cleanup: None, .. } + | InlineAsm { destination: None, cleanup: Some(ref mut t), .. } => { + Some(t).into_iter().chain(&mut []) + } + Call { target: Some(ref mut t), cleanup: Some(ref mut u), .. } + | Yield { resume: ref mut t, drop: Some(ref mut u), .. } + | DropAndReplace { target: ref mut t, unwind: Some(ref mut u), .. } + | Drop { target: ref mut t, unwind: Some(ref mut u), .. } + | Assert { target: ref mut t, cleanup: Some(ref mut u), .. } + | FalseUnwind { real_target: ref mut t, unwind: Some(ref mut u) } + | InlineAsm { destination: Some(ref mut t), cleanup: Some(ref mut u), .. } => { + Some(t).into_iter().chain(slice::from_mut(u)) + } + SwitchInt { ref mut targets, .. } => None.into_iter().chain(&mut targets.targets), + FalseEdge { ref mut real_target, ref mut imaginary_target } => { + Some(real_target).into_iter().chain(slice::from_mut(imaginary_target)) + } + } + } + + pub fn unwind(&self) -> Option<&Option<BasicBlock>> { + match *self { + TerminatorKind::Goto { .. } + | TerminatorKind::Resume + | TerminatorKind::Abort + | TerminatorKind::Return + | TerminatorKind::Unreachable + | TerminatorKind::GeneratorDrop + | TerminatorKind::Yield { .. } + | TerminatorKind::SwitchInt { .. } + | TerminatorKind::FalseEdge { .. } => None, + TerminatorKind::Call { cleanup: ref unwind, .. } + | TerminatorKind::Assert { cleanup: ref unwind, .. } + | TerminatorKind::DropAndReplace { ref unwind, .. } + | TerminatorKind::Drop { ref unwind, .. } + | TerminatorKind::FalseUnwind { ref unwind, .. } + | TerminatorKind::InlineAsm { cleanup: ref unwind, .. } => Some(unwind), + } + } + + pub fn unwind_mut(&mut self) -> Option<&mut Option<BasicBlock>> { + match *self { + TerminatorKind::Goto { .. } + | TerminatorKind::Resume + | TerminatorKind::Abort + | TerminatorKind::Return + | TerminatorKind::Unreachable + | TerminatorKind::GeneratorDrop + | TerminatorKind::Yield { .. } + | TerminatorKind::SwitchInt { .. } + | TerminatorKind::FalseEdge { .. } => None, + TerminatorKind::Call { cleanup: ref mut unwind, .. } + | TerminatorKind::Assert { cleanup: ref mut unwind, .. } + | TerminatorKind::DropAndReplace { ref mut unwind, .. } + | TerminatorKind::Drop { ref mut unwind, .. } + | TerminatorKind::FalseUnwind { ref mut unwind, .. } + | TerminatorKind::InlineAsm { cleanup: ref mut unwind, .. } => Some(unwind), + } + } + + pub fn as_switch(&self) -> Option<(&Operand<'tcx>, Ty<'tcx>, &SwitchTargets)> { + match self { + TerminatorKind::SwitchInt { discr, switch_ty, targets } => { + Some((discr, *switch_ty, targets)) + } + _ => None, + } + } + + pub fn as_goto(&self) -> Option<BasicBlock> { + match self { + TerminatorKind::Goto { target } => Some(*target), + _ => None, + } + } +} + +impl<'tcx> Debug for TerminatorKind<'tcx> { + fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result { + self.fmt_head(fmt)?; + let successor_count = self.successors().count(); + let labels = self.fmt_successor_labels(); + assert_eq!(successor_count, labels.len()); + + match successor_count { + 0 => Ok(()), + + 1 => write!(fmt, " -> {:?}", self.successors().next().unwrap()), + + _ => { + write!(fmt, " -> [")?; + for (i, target) in self.successors().enumerate() { + if i > 0 { + write!(fmt, ", ")?; + } + write!(fmt, "{}: {:?}", labels[i], target)?; + } + write!(fmt, "]") + } + } + } +} + +impl<'tcx> TerminatorKind<'tcx> { + /// Writes the "head" part of the terminator; that is, its name and the data it uses to pick the + /// successor basic block, if any. The only information not included is the list of possible + /// successors, which may be rendered differently between the text and the graphviz format. + pub fn fmt_head<W: Write>(&self, fmt: &mut W) -> fmt::Result { + use self::TerminatorKind::*; + match self { + Goto { .. } => write!(fmt, "goto"), + SwitchInt { discr, .. } => write!(fmt, "switchInt({:?})", discr), + Return => write!(fmt, "return"), + GeneratorDrop => write!(fmt, "generator_drop"), + Resume => write!(fmt, "resume"), + Abort => write!(fmt, "abort"), + Yield { value, resume_arg, .. } => write!(fmt, "{:?} = yield({:?})", resume_arg, value), + Unreachable => write!(fmt, "unreachable"), + Drop { place, .. } => write!(fmt, "drop({:?})", place), + DropAndReplace { place, value, .. } => { + write!(fmt, "replace({:?} <- {:?})", place, value) + } + Call { func, args, destination, .. } => { + write!(fmt, "{:?} = ", destination)?; + write!(fmt, "{:?}(", func)?; + for (index, arg) in args.iter().enumerate() { + if index > 0 { + write!(fmt, ", ")?; + } + write!(fmt, "{:?}", arg)?; + } + write!(fmt, ")") + } + Assert { cond, expected, msg, .. } => { + write!(fmt, "assert(")?; + if !expected { + write!(fmt, "!")?; + } + write!(fmt, "{:?}, ", cond)?; + msg.fmt_assert_args(fmt)?; + write!(fmt, ")") + } + FalseEdge { .. } => write!(fmt, "falseEdge"), + FalseUnwind { .. } => write!(fmt, "falseUnwind"), + InlineAsm { template, ref operands, options, .. } => { + write!(fmt, "asm!(\"{}\"", InlineAsmTemplatePiece::to_string(template))?; + for op in operands { + write!(fmt, ", ")?; + let print_late = |&late| if late { "late" } else { "" }; + match op { + InlineAsmOperand::In { reg, value } => { + write!(fmt, "in({}) {:?}", reg, value)?; + } + InlineAsmOperand::Out { reg, late, place: Some(place) } => { + write!(fmt, "{}out({}) {:?}", print_late(late), reg, place)?; + } + InlineAsmOperand::Out { reg, late, place: None } => { + write!(fmt, "{}out({}) _", print_late(late), reg)?; + } + InlineAsmOperand::InOut { + reg, + late, + in_value, + out_place: Some(out_place), + } => { + write!( + fmt, + "in{}out({}) {:?} => {:?}", + print_late(late), + reg, + in_value, + out_place + )?; + } + InlineAsmOperand::InOut { reg, late, in_value, out_place: None } => { + write!(fmt, "in{}out({}) {:?} => _", print_late(late), reg, in_value)?; + } + InlineAsmOperand::Const { value } => { + write!(fmt, "const {:?}", value)?; + } + InlineAsmOperand::SymFn { value } => { + write!(fmt, "sym_fn {:?}", value)?; + } + InlineAsmOperand::SymStatic { def_id } => { + write!(fmt, "sym_static {:?}", def_id)?; + } + } + } + write!(fmt, ", options({:?}))", options) + } + } + } + + /// Returns the list of labels for the edges to the successor basic blocks. + pub fn fmt_successor_labels(&self) -> Vec<Cow<'static, str>> { + use self::TerminatorKind::*; + match *self { + Return | Resume | Abort | Unreachable | GeneratorDrop => vec![], + Goto { .. } => vec!["".into()], + SwitchInt { ref targets, switch_ty, .. } => ty::tls::with(|tcx| { + let param_env = ty::ParamEnv::empty(); + let switch_ty = tcx.lift(switch_ty).unwrap(); + let size = tcx.layout_of(param_env.and(switch_ty)).unwrap().size; + targets + .values + .iter() + .map(|&u| { + mir::ConstantKind::from_scalar(tcx, Scalar::from_uint(u, size), switch_ty) + .to_string() + .into() + }) + .chain(iter::once("otherwise".into())) + .collect() + }), + Call { target: Some(_), cleanup: Some(_), .. } => { + vec!["return".into(), "unwind".into()] + } + Call { target: Some(_), cleanup: None, .. } => vec!["return".into()], + Call { target: None, cleanup: Some(_), .. } => vec!["unwind".into()], + Call { target: None, cleanup: None, .. } => vec![], + Yield { drop: Some(_), .. } => vec!["resume".into(), "drop".into()], + Yield { drop: None, .. } => vec!["resume".into()], + DropAndReplace { unwind: None, .. } | Drop { unwind: None, .. } => { + vec!["return".into()] + } + DropAndReplace { unwind: Some(_), .. } | Drop { unwind: Some(_), .. } => { + vec!["return".into(), "unwind".into()] + } + Assert { cleanup: None, .. } => vec!["".into()], + Assert { .. } => vec!["success".into(), "unwind".into()], + FalseEdge { .. } => vec!["real".into(), "imaginary".into()], + FalseUnwind { unwind: Some(_), .. } => vec!["real".into(), "cleanup".into()], + FalseUnwind { unwind: None, .. } => vec!["real".into()], + InlineAsm { destination: Some(_), cleanup: Some(_), .. } => { + vec!["return".into(), "unwind".into()] + } + InlineAsm { destination: Some(_), cleanup: None, .. } => vec!["return".into()], + InlineAsm { destination: None, cleanup: Some(_), .. } => vec!["unwind".into()], + InlineAsm { destination: None, cleanup: None, .. } => vec![], + } + } +} |