48064d4498
These are all functions with a single callsite, where having a separate function does nothing to help with readability. These changes make the code a little shorter and easier to read.
78 lines
2.8 KiB
Rust
78 lines
2.8 KiB
Rust
use rustc_index::{Idx, IndexVec};
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use rustc_middle::mir::*;
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use rustc_middle::ty::TyCtxt;
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use tracing::debug;
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#[derive(PartialEq)]
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pub(super) enum AddCallGuards {
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AllCallEdges,
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CriticalCallEdges,
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}
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pub(super) use self::AddCallGuards::*;
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/**
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* Breaks outgoing critical edges for call terminators in the MIR.
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*
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* Critical edges are edges that are neither the only edge leaving a
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* block, nor the only edge entering one.
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*
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* When you want something to happen "along" an edge, you can either
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* do at the end of the predecessor block, or at the start of the
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* successor block. Critical edges have to be broken in order to prevent
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* "edge actions" from affecting other edges. We need this for calls that are
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* codegened to LLVM invoke instructions, because invoke is a block terminator
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* in LLVM so we can't insert any code to handle the call's result into the
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* block that performs the call.
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*
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* This function will break those edges by inserting new blocks along them.
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*
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* NOTE: Simplify CFG will happily undo most of the work this pass does.
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*
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*/
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impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
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fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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let mut pred_count: IndexVec<_, _> =
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body.basic_blocks.predecessors().iter().map(|ps| ps.len()).collect();
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pred_count[START_BLOCK] += 1;
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// We need a place to store the new blocks generated
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let mut new_blocks = Vec::new();
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let cur_len = body.basic_blocks.len();
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for block in body.basic_blocks_mut() {
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match block.terminator {
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Some(Terminator {
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kind: TerminatorKind::Call { target: Some(ref mut destination), unwind, .. },
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source_info,
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}) if pred_count[*destination] > 1
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&& (matches!(
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unwind,
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UnwindAction::Cleanup(_) | UnwindAction::Terminate(_)
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) || self == &AllCallEdges) =>
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{
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// It's a critical edge, break it
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let call_guard = BasicBlockData {
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statements: vec![],
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is_cleanup: block.is_cleanup,
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terminator: Some(Terminator {
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source_info,
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kind: TerminatorKind::Goto { target: *destination },
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}),
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};
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// Get the index it will be when inserted into the MIR
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let idx = cur_len + new_blocks.len();
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new_blocks.push(call_guard);
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*destination = BasicBlock::new(idx);
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}
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_ => {}
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}
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}
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debug!("Broke {} N edges", new_blocks.len());
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body.basic_blocks_mut().extend(new_blocks);
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}
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}
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