2aae619edb
Because that's now the only crate that uses it. Moving stuff out of `rustc_middle` is always welcome. I chose to use `impl crate::MirPass`/`impl crate::MirLint` (with explicit `crate::`) everywhere because that's the only mention of `MirPass`/`MirLint` used in all of these files. (Prior to this change, `MirPass` was mostly imported via `use rustc_middle::mir::*` items.)
58 lines
1.9 KiB
Rust
58 lines
1.9 KiB
Rust
//! A pass that inserts the `ConstEvalCounter` instruction into any blocks that have a back edge
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//! (thus indicating there is a loop in the CFG), or whose terminator is a function call.
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use rustc_data_structures::graph::dominators::Dominators;
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use rustc_middle::mir::{
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BasicBlock, BasicBlockData, Body, Statement, StatementKind, TerminatorKind,
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};
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use rustc_middle::ty::TyCtxt;
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use tracing::instrument;
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pub struct CtfeLimit;
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impl<'tcx> crate::MirPass<'tcx> for CtfeLimit {
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#[instrument(skip(self, _tcx, body))]
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fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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let doms = body.basic_blocks.dominators();
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let indices: Vec<BasicBlock> = body
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.basic_blocks
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.iter_enumerated()
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.filter_map(|(node, node_data)| {
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if matches!(node_data.terminator().kind, TerminatorKind::Call { .. })
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// Back edges in a CFG indicate loops
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|| has_back_edge(doms, node, node_data)
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{
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Some(node)
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} else {
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None
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}
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})
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.collect();
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for index in indices {
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insert_counter(
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body.basic_blocks_mut()
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.get_mut(index)
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.expect("basic_blocks index {index} should exist"),
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);
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}
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}
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}
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fn has_back_edge(
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doms: &Dominators<BasicBlock>,
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node: BasicBlock,
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node_data: &BasicBlockData<'_>,
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) -> bool {
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if !doms.is_reachable(node) {
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return false;
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}
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// Check if any of the dominators of the node are also the node's successor.
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node_data.terminator().successors().any(|succ| doms.dominates(succ, node))
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}
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fn insert_counter(basic_block_data: &mut BasicBlockData<'_>) {
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basic_block_data.statements.push(Statement {
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source_info: basic_block_data.terminator().source_info,
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kind: StatementKind::ConstEvalCounter,
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});
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}
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