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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,144 @@ | ||
| use crate::liveness::{LiveNode, Variable}; | ||
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| #[derive(Clone, Copy)] | ||
| pub(super) struct RWU { | ||
| pub(super) reader: bool, | ||
| pub(super) writer: bool, | ||
| pub(super) used: bool, | ||
| } | ||
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||
| /// Conceptually, this is like a `Vec<Vec<RWU>>`. But the number of | ||
| /// RWU`s can get very large, so it uses a more compact representation. | ||
| pub(super) struct RWUTable { | ||
| /// Total number of live nodes. | ||
| live_nodes: usize, | ||
| /// Total number of variables. | ||
| vars: usize, | ||
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| /// A compressed representation of `RWU`s. | ||
| /// | ||
| /// Each word represents 2 different `RWU`s packed together. Each packed RWU | ||
| /// is stored in 4 bits: a reader bit, a writer bit, a used bit and a | ||
| /// padding bit. | ||
| /// | ||
| /// The data for each live node is contiguous and starts at a word boundary, | ||
| /// so there might be an unused space left. | ||
| words: Vec<u8>, | ||
| /// Number of words per each live node. | ||
| live_node_words: usize, | ||
| } | ||
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| impl RWUTable { | ||
| const RWU_READER: u8 = 0b0001; | ||
| const RWU_WRITER: u8 = 0b0010; | ||
| const RWU_USED: u8 = 0b0100; | ||
| const RWU_MASK: u8 = 0b1111; | ||
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| /// Size of packed RWU in bits. | ||
| const RWU_BITS: usize = 4; | ||
| /// Size of a word in bits. | ||
| const WORD_BITS: usize = std::mem::size_of::<u8>() * 8; | ||
| /// Number of packed RWUs that fit into a single word. | ||
| const WORD_RWU_COUNT: usize = Self::WORD_BITS / Self::RWU_BITS; | ||
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| pub(super) fn new(live_nodes: usize, vars: usize) -> RWUTable { | ||
| let live_node_words = (vars + Self::WORD_RWU_COUNT - 1) / Self::WORD_RWU_COUNT; | ||
| Self { live_nodes, vars, live_node_words, words: vec![0u8; live_node_words * live_nodes] } | ||
| } | ||
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| fn word_and_shift(&self, ln: LiveNode, var: Variable) -> (usize, u32) { | ||
| assert!(ln.index() < self.live_nodes); | ||
| assert!(var.index() < self.vars); | ||
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| let var = var.index(); | ||
| let word = var / Self::WORD_RWU_COUNT; | ||
| let shift = Self::RWU_BITS * (var % Self::WORD_RWU_COUNT); | ||
| (ln.index() * self.live_node_words + word, shift as u32) | ||
| } | ||
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| fn pick2_rows_mut(&mut self, a: LiveNode, b: LiveNode) -> (&mut [u8], &mut [u8]) { | ||
| assert!(a.index() < self.live_nodes); | ||
| assert!(b.index() < self.live_nodes); | ||
| assert!(a != b); | ||
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| let a_start = a.index() * self.live_node_words; | ||
| let b_start = b.index() * self.live_node_words; | ||
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| unsafe { | ||
| let ptr = self.words.as_mut_ptr(); | ||
| ( | ||
| std::slice::from_raw_parts_mut(ptr.add(a_start), self.live_node_words), | ||
| std::slice::from_raw_parts_mut(ptr.add(b_start), self.live_node_words), | ||
| ) | ||
| } | ||
| } | ||
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| pub(super) fn copy(&mut self, dst: LiveNode, src: LiveNode) { | ||
| if dst == src { | ||
| return; | ||
| } | ||
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| let (dst_row, src_row) = self.pick2_rows_mut(dst, src); | ||
| dst_row.copy_from_slice(src_row); | ||
| } | ||
|
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| /// Sets `dst` to the union of `dst` and `src`, returns true if `dst` was | ||
| /// changed. | ||
| pub(super) fn union(&mut self, dst: LiveNode, src: LiveNode) -> bool { | ||
| if dst == src { | ||
| return false; | ||
| } | ||
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| let mut changed = false; | ||
| let (dst_row, src_row) = self.pick2_rows_mut(dst, src); | ||
| for (dst_word, src_word) in dst_row.iter_mut().zip(src_row.iter()) { | ||
| let old = *dst_word; | ||
| let new = *dst_word | src_word; | ||
| *dst_word = new; | ||
| changed |= old != new; | ||
| } | ||
| changed | ||
| } | ||
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| pub(super) fn get_reader(&self, ln: LiveNode, var: Variable) -> bool { | ||
| let (word, shift) = self.word_and_shift(ln, var); | ||
| (self.words[word] >> shift) & Self::RWU_READER != 0 | ||
| } | ||
|
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| pub(super) fn get_writer(&self, ln: LiveNode, var: Variable) -> bool { | ||
| let (word, shift) = self.word_and_shift(ln, var); | ||
| (self.words[word] >> shift) & Self::RWU_WRITER != 0 | ||
| } | ||
|
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| pub(super) fn get_used(&self, ln: LiveNode, var: Variable) -> bool { | ||
| let (word, shift) = self.word_and_shift(ln, var); | ||
| (self.words[word] >> shift) & Self::RWU_USED != 0 | ||
| } | ||
|
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| pub(super) fn get(&self, ln: LiveNode, var: Variable) -> RWU { | ||
| let (word, shift) = self.word_and_shift(ln, var); | ||
| let rwu_packed = self.words[word] >> shift; | ||
| RWU { | ||
| reader: rwu_packed & Self::RWU_READER != 0, | ||
| writer: rwu_packed & Self::RWU_WRITER != 0, | ||
| used: rwu_packed & Self::RWU_USED != 0, | ||
| } | ||
| } | ||
|
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| pub(super) fn set(&mut self, ln: LiveNode, var: Variable, rwu: RWU) { | ||
| let mut packed = 0; | ||
| if rwu.reader { | ||
| packed |= Self::RWU_READER; | ||
| } | ||
| if rwu.writer { | ||
| packed |= Self::RWU_WRITER; | ||
| } | ||
| if rwu.used { | ||
| packed |= Self::RWU_USED; | ||
| } | ||
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| let (word, shift) = self.word_and_shift(ln, var); | ||
| let word = &mut self.words[word]; | ||
| *word = (*word & !(Self::RWU_MASK << shift)) | (packed << shift) | ||
| } | ||
| } |