bjoernager/rust
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Improve efficiency of has_back_edge(...)

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This commit is contained in:
Bryan Garza 2023-01-06 22:04:25 +00:00
parent 7618163a1c
commit 1bbd655888
2 changed files with 18 additions and 10 deletions
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21
compiler/rustc_mir_transform/src/ctfe_limit.rs
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@ -2,8 +2,9 @@
//! (thus indicating there is a loop in the CFG), or whose terminator is a function call.
use crate::MirPass;
use rustc_data_structures::graph::dominators::Dominators;
use rustc_middle::mir::{
BasicBlock, BasicBlockData, BasicBlocks, Body, Statement, StatementKind, TerminatorKind,
BasicBlock, BasicBlockData, Body, Statement, StatementKind, TerminatorKind,
};
use rustc_middle::ty::TyCtxt;
@ -12,13 +13,14 @@ pub struct CtfeLimit;
impl<'tcx> MirPass<'tcx> for CtfeLimit {
#[instrument(skip(self, _tcx, body))]
fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let doms = body.basic_blocks.dominators();
let indices: Vec<BasicBlock> = body
.basic_blocks
.iter_enumerated()
.filter_map(|(node, node_data)| {
if matches!(node_data.terminator().kind, TerminatorKind::Call { .. })
// Back edges in a CFG indicate loops
|| has_back_edge(&body.basic_blocks, node, &node_data)
|| has_back_edge(&doms, node, &node_data)
{
Some(node)
} else {
@ -37,17 +39,16 @@ impl<'tcx> MirPass<'tcx> for CtfeLimit {
}
fn has_back_edge(
basic_blocks: &BasicBlocks<'_>,
doms: &Dominators<BasicBlock>,
node: BasicBlock,
node_data: &BasicBlockData<'_>,
) -> bool {
let doms = basic_blocks.dominators();
basic_blocks.indices().any(|potential_dom| {
doms.is_reachable(potential_dom)
&& doms.is_reachable(node)
&& doms.is_dominated_by(node, potential_dom)
&& node_data.terminator().successors().into_iter().any(|succ| succ == potential_dom)
})
if !doms.is_reachable(node) {
return false;
}
// Check if any of the dominators of the node are also the node's successor.
doms.dominators(node)
.any(|dom| node_data.terminator().successors().into_iter().any(|succ| succ == dom))
}
fn insert_counter(basic_block_data: &mut BasicBlockData<'_>) {