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Calculate predecessor count directly #138076

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Merged
merged 2 commits into from
Mar 13, 2025
Merged

Calculate predecessor count directly #138076

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508b803
Remove start block special case
tmiasko Mar 5, 2025
5bae3ad
Calculate predecessor count directly
tmiasko Mar 5, 2025
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9 changes: 6 additions & 3 deletions compiler/rustc_mir_transform/src/add_call_guards.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -32,9 +32,12 @@ pub(super) use self::AddCallGuards::*;

impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let mut pred_count: IndexVec<_, _> =
body.basic_blocks.predecessors().iter().map(|ps| ps.len()).collect();
pred_count[START_BLOCK] += 1;
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Start block has no predecessors since #88968, so this special case is no longer necessary.

let mut pred_count = IndexVec::from_elem(0u8, &body.basic_blocks);
for (_, data) in body.basic_blocks.iter_enumerated() {
for succ in data.terminator().successors() {
pred_count[succ] = pred_count[succ].saturating_add(1);
}
}

// We need a place to store the new blocks generated
let mut new_blocks = Vec::new();
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