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Move RWUTable to a separate module
This commit is contained in:
Tomasz Miąsko
parent
1700ca07c6
commit
c7d7bc917d
@ -105,6 +105,8 @@ use std::io;
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use std::io::prelude::*;
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use std::rc::Rc;
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mod rwu_table;
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rustc_index::newtype_index! {
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pub struct Variable {
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DEBUG_FORMAT = "v({})",
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@ -468,149 +470,6 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
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// Actually we compute just a bit more than just liveness, but we use
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// the same basic propagation framework in all cases.
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#[derive(Clone, Copy)]
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struct RWU {
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reader: bool,
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writer: bool,
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used: bool,
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}
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/// Conceptually, this is like a `Vec<Vec<RWU>>`. But the number of
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/// RWU`s can get very large, so it uses a more compact representation.
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struct RWUTable {
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/// Total number of live nodes.
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live_nodes: usize,
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/// Total number of variables.
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vars: usize,
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/// A compressed representation of `RWU`s.
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///
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/// Each word represents 2 different `RWU`s packed together. Each packed RWU
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/// is stored in 4 bits: a reader bit, a writer bit, a used bit and a
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/// padding bit.
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///
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/// The data for each live node is contiguous and starts at a word boundary,
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/// so there might be an unused space left.
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words: Vec<u8>,
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/// Number of words per each live node.
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live_node_words: usize,
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}
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impl RWUTable {
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const RWU_READER: u8 = 0b0001;
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const RWU_WRITER: u8 = 0b0010;
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const RWU_USED: u8 = 0b0100;
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const RWU_MASK: u8 = 0b1111;
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/// Size of packed RWU in bits.
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const RWU_BITS: usize = 4;
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/// Size of a word in bits.
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const WORD_BITS: usize = std::mem::size_of::<u8>() * 8;
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/// Number of packed RWUs that fit into a single word.
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const WORD_RWU_COUNT: usize = Self::WORD_BITS / Self::RWU_BITS;
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fn new(live_nodes: usize, vars: usize) -> RWUTable {
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let live_node_words = (vars + Self::WORD_RWU_COUNT - 1) / Self::WORD_RWU_COUNT;
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Self { live_nodes, vars, live_node_words, words: vec![0u8; live_node_words * live_nodes] }
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}
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fn word_and_shift(&self, ln: LiveNode, var: Variable) -> (usize, u32) {
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assert!(ln.index() < self.live_nodes);
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assert!(var.index() < self.vars);
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let var = var.index();
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let word = var / Self::WORD_RWU_COUNT;
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let shift = Self::RWU_BITS * (var % Self::WORD_RWU_COUNT);
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(ln.index() * self.live_node_words + word, shift as u32)
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}
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fn pick2_rows_mut(&mut self, a: LiveNode, b: LiveNode) -> (&mut [u8], &mut [u8]) {
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assert!(a.index() < self.live_nodes);
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assert!(b.index() < self.live_nodes);
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assert!(a != b);
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let a_start = a.index() * self.live_node_words;
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let b_start = b.index() * self.live_node_words;
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unsafe {
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let ptr = self.words.as_mut_ptr();
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(
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std::slice::from_raw_parts_mut(ptr.add(a_start), self.live_node_words),
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std::slice::from_raw_parts_mut(ptr.add(b_start), self.live_node_words),
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)
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}
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}
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fn copy(&mut self, dst: LiveNode, src: LiveNode) {
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if dst == src {
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return;
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}
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let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
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dst_row.copy_from_slice(src_row);
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}
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/// Sets `dst` to the union of `dst` and `src`, returns true if `dst` was
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/// changed.
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fn union(&mut self, dst: LiveNode, src: LiveNode) -> bool {
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if dst == src {
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return false;
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}
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let mut changed = false;
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let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
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for (dst_word, src_word) in dst_row.iter_mut().zip(src_row.iter()) {
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let old = *dst_word;
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let new = *dst_word | src_word;
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*dst_word = new;
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changed |= old != new;
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}
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changed
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}
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fn get_reader(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_READER != 0
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}
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fn get_writer(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_WRITER != 0
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}
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fn get_used(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_USED != 0
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}
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fn get(&self, ln: LiveNode, var: Variable) -> RWU {
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let (word, shift) = self.word_and_shift(ln, var);
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let rwu_packed = self.words[word] >> shift;
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RWU {
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reader: rwu_packed & Self::RWU_READER != 0,
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writer: rwu_packed & Self::RWU_WRITER != 0,
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used: rwu_packed & Self::RWU_USED != 0,
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}
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}
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fn set(&mut self, ln: LiveNode, var: Variable, rwu: RWU) {
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let mut packed = 0;
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if rwu.reader {
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packed |= Self::RWU_READER;
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}
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if rwu.writer {
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packed |= Self::RWU_WRITER;
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}
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if rwu.used {
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packed |= Self::RWU_USED;
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}
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let (word, shift) = self.word_and_shift(ln, var);
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let word = &mut self.words[word];
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*word = (*word & !(Self::RWU_MASK << shift)) | (packed << shift)
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}
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}
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const ACC_READ: u32 = 1;
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const ACC_WRITE: u32 = 2;
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const ACC_USE: u32 = 4;
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@ -623,7 +482,7 @@ struct Liveness<'a, 'tcx> {
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upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
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closure_captures: Option<&'tcx FxIndexMap<hir::HirId, ty::UpvarId>>,
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successors: IndexVec<LiveNode, Option<LiveNode>>,
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rwu_table: RWUTable,
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rwu_table: rwu_table::RWUTable,
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/// A live node representing a point of execution before closure entry &
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/// after closure exit. Used to calculate liveness of captured variables
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@ -661,7 +520,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
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upvars,
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closure_captures,
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successors: IndexVec::from_elem_n(None, num_live_nodes),
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rwu_table: RWUTable::new(num_live_nodes, num_vars),
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rwu_table: rwu_table::RWUTable::new(num_live_nodes, num_vars),
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closure_ln,
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exit_ln,
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break_ln: Default::default(),
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@ -802,7 +661,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
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// this) so we just clear out all the data.
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fn define(&mut self, writer: LiveNode, var: Variable) {
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let used = self.rwu_table.get_used(writer, var);
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self.rwu_table.set(writer, var, RWU { reader: false, writer: false, used });
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self.rwu_table.set(writer, var, rwu_table::RWU { reader: false, writer: false, used });
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debug!("{:?} defines {:?}: {}", writer, var, self.ln_str(writer));
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}
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144
compiler/rustc_passes/src/liveness/rwu_table.rs
Normal file
144
compiler/rustc_passes/src/liveness/rwu_table.rs
Normal file
@ -0,0 +1,144 @@
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use crate::liveness::{LiveNode, Variable};
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#[derive(Clone, Copy)]
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pub(super) struct RWU {
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pub(super) reader: bool,
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pub(super) writer: bool,
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pub(super) used: bool,
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}
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/// Conceptually, this is like a `Vec<Vec<RWU>>`. But the number of
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/// RWU`s can get very large, so it uses a more compact representation.
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pub(super) struct RWUTable {
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/// Total number of live nodes.
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live_nodes: usize,
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/// Total number of variables.
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vars: usize,
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/// A compressed representation of `RWU`s.
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///
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/// Each word represents 2 different `RWU`s packed together. Each packed RWU
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/// is stored in 4 bits: a reader bit, a writer bit, a used bit and a
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/// padding bit.
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///
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/// The data for each live node is contiguous and starts at a word boundary,
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/// so there might be an unused space left.
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words: Vec<u8>,
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/// Number of words per each live node.
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live_node_words: usize,
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}
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impl RWUTable {
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const RWU_READER: u8 = 0b0001;
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const RWU_WRITER: u8 = 0b0010;
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const RWU_USED: u8 = 0b0100;
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const RWU_MASK: u8 = 0b1111;
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/// Size of packed RWU in bits.
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const RWU_BITS: usize = 4;
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/// Size of a word in bits.
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const WORD_BITS: usize = std::mem::size_of::<u8>() * 8;
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/// Number of packed RWUs that fit into a single word.
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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 {
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let live_node_words = (vars + Self::WORD_RWU_COUNT - 1) / Self::WORD_RWU_COUNT;
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Self { live_nodes, vars, live_node_words, words: vec![0u8; live_node_words * live_nodes] }
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}
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fn word_and_shift(&self, ln: LiveNode, var: Variable) -> (usize, u32) {
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assert!(ln.index() < self.live_nodes);
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assert!(var.index() < self.vars);
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let var = var.index();
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let word = var / Self::WORD_RWU_COUNT;
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let shift = Self::RWU_BITS * (var % Self::WORD_RWU_COUNT);
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(ln.index() * self.live_node_words + word, shift as u32)
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}
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fn pick2_rows_mut(&mut self, a: LiveNode, b: LiveNode) -> (&mut [u8], &mut [u8]) {
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assert!(a.index() < self.live_nodes);
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assert!(b.index() < self.live_nodes);
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assert!(a != b);
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let a_start = a.index() * self.live_node_words;
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let b_start = b.index() * self.live_node_words;
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unsafe {
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let ptr = self.words.as_mut_ptr();
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(
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std::slice::from_raw_parts_mut(ptr.add(a_start), self.live_node_words),
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std::slice::from_raw_parts_mut(ptr.add(b_start), self.live_node_words),
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)
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}
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}
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pub(super) fn copy(&mut self, dst: LiveNode, src: LiveNode) {
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if dst == src {
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return;
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}
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let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
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dst_row.copy_from_slice(src_row);
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}
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/// Sets `dst` to the union of `dst` and `src`, returns true if `dst` was
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/// changed.
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pub(super) fn union(&mut self, dst: LiveNode, src: LiveNode) -> bool {
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if dst == src {
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return false;
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}
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let mut changed = false;
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let (dst_row, src_row) = self.pick2_rows_mut(dst, src);
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for (dst_word, src_word) in dst_row.iter_mut().zip(src_row.iter()) {
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let old = *dst_word;
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let new = *dst_word | src_word;
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*dst_word = new;
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changed |= old != new;
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}
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changed
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}
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pub(super) fn get_reader(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_READER != 0
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}
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pub(super) fn get_writer(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_WRITER != 0
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}
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pub(super) fn get_used(&self, ln: LiveNode, var: Variable) -> bool {
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let (word, shift) = self.word_and_shift(ln, var);
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(self.words[word] >> shift) & Self::RWU_USED != 0
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}
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pub(super) fn get(&self, ln: LiveNode, var: Variable) -> RWU {
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let (word, shift) = self.word_and_shift(ln, var);
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let rwu_packed = self.words[word] >> shift;
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RWU {
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reader: rwu_packed & Self::RWU_READER != 0,
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writer: rwu_packed & Self::RWU_WRITER != 0,
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used: rwu_packed & Self::RWU_USED != 0,
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}
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}
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pub(super) fn set(&mut self, ln: LiveNode, var: Variable, rwu: RWU) {
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let mut packed = 0;
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if rwu.reader {
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packed |= Self::RWU_READER;
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}
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if rwu.writer {
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packed |= Self::RWU_WRITER;
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}
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if rwu.used {
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packed |= Self::RWU_USED;
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}
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let (word, shift) = self.word_and_shift(ln, var);
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let word = &mut self.words[word];
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*word = (*word & !(Self::RWU_MASK << shift)) | (packed << shift)
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}
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}
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