55 lines
1.4 KiB
Rust
55 lines
1.4 KiB
Rust
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//! Fast postorder computation.
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// Borrowed from regalloc2's postorder.rs, which is also Apache-2.0
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// with LLVM-exception.
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use crate::ir::BlockId;
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use smallvec::{smallvec, SmallVec};
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pub fn calculate<'a, SuccFn: Fn(BlockId) -> &'a [BlockId]>(
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num_blocks: usize,
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entry: BlockId,
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succ_blocks: SuccFn,
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) -> Vec<BlockId> {
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let mut ret = vec![];
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// State: visited-block map, and explicit DFS stack.
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let mut visited = vec![];
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visited.resize(num_blocks, false);
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struct State<'a> {
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block: BlockId,
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succs: &'a [BlockId],
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next_succ: usize,
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}
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let mut stack: SmallVec<[State; 64]> = smallvec![];
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visited[entry] = true;
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stack.push(State {
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block: entry,
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succs: succ_blocks(entry),
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next_succ: 0,
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});
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while let Some(ref mut state) = stack.last_mut() {
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// Perform one action: push to new succ, skip an already-visited succ, or pop.
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if state.next_succ < state.succs.len() {
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let succ = state.succs[state.next_succ];
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state.next_succ += 1;
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if !visited[succ] {
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visited[succ] = true;
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stack.push(State {
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block: succ,
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succs: succ_blocks(succ),
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next_succ: 0,
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});
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}
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} else {
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ret.push(state.block);
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stack.pop();
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}
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}
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ret
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}
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