1098eafb45
WebAssembly doesn't have non-dense jump tables, and higher-level users are better served by the facilities in lib/frontend/src/switch.rs for working with non-dense switches. This eliminates the concept of "absent" jump table entries, which were represented as "0" in the text format. Also, jump table contents are now enclosed in `[` and `]`, so that we can unambiguously display empty jump tables. Previously, empty jump tables were displayed as if they had a single absent entry.
120 lines
2.9 KiB
Rust
120 lines
2.9 KiB
Rust
//! Jump table representation.
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//!
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//! Jump tables are declared in the preamble and assigned an `ir::entities::JumpTable` reference.
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//! The actual table of destinations is stored in a `JumpTableData` struct defined in this module.
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use ir::entities::Ebb;
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use std::fmt::{self, Display, Formatter};
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use std::slice::{Iter, IterMut};
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use std::vec::Vec;
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/// Contents of a jump table.
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///
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/// All jump tables use 0-based indexing and densely populated.
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#[derive(Clone)]
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pub struct JumpTableData {
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// Table entries.
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table: Vec<Ebb>,
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}
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impl JumpTableData {
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/// Create a new empty jump table.
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pub fn new() -> Self {
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Self { table: Vec::new() }
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}
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/// Create a new empty jump table with the specified capacity.
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pub fn with_capacity(capacity: usize) -> Self {
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Self {
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table: Vec::with_capacity(capacity),
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}
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}
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/// Get the number of table entries.
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pub fn len(&self) -> usize {
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self.table.len()
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}
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/// Append a table entry.
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pub fn push_entry(&mut self, dest: Ebb) {
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self.table.push(dest)
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}
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/// Checks if any of the entries branch to `ebb`.
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pub fn branches_to(&self, ebb: Ebb) -> bool {
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self.table.iter().any(|target_ebb| *target_ebb == ebb)
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}
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/// Access the whole table as a slice.
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pub fn as_slice(&self) -> &[Ebb] {
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self.table.as_slice()
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}
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/// Access the whole table as a mutable slice.
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pub fn as_mut_slice(&mut self) -> &mut [Ebb] {
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self.table.as_mut_slice()
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}
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/// Returns an iterator over the table.
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pub fn iter(&self) -> Iter<Ebb> {
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self.table.iter()
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}
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/// Returns an iterator that allows modifying each value.
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pub fn iter_mut(&mut self) -> IterMut<Ebb> {
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self.table.iter_mut()
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}
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}
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impl Display for JumpTableData {
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fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
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write!(fmt, "jump_table [")?;
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match self.table.first() {
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None => (),
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Some(first) => write!(fmt, "{}", first)?,
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}
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for ebb in self.table.iter().skip(1) {
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write!(fmt, ", {}", ebb)?;
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}
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write!(fmt, "]")
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}
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}
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#[cfg(test)]
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mod tests {
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use super::JumpTableData;
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use entity::EntityRef;
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use ir::Ebb;
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use std::string::ToString;
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#[test]
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fn empty() {
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let jt = JumpTableData::new();
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assert_eq!(jt.as_slice().get(0), None);
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assert_eq!(jt.as_slice().get(10), None);
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assert_eq!(jt.to_string(), "jump_table []");
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let v = jt.as_slice();
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assert_eq!(v, []);
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}
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#[test]
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fn insert() {
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let e1 = Ebb::new(1);
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let e2 = Ebb::new(2);
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let mut jt = JumpTableData::new();
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jt.push_entry(e1);
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jt.push_entry(e2);
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jt.push_entry(e1);
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assert_eq!(jt.to_string(), "jump_table [ebb1, ebb2, ebb1]");
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let v = jt.as_slice();
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assert_eq!(v, [e1, e2, e1]);
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}
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}
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