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Auto merge of #123175 - Nilstrieb:debug-strict-overflow, r=wesleywiser

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Add add/sub methods that only panic with debug assertions to rustc

This mitigates the perf impact of enabling overflow checks on rustc. The change to use overflow checks will be done in a later PR.

For rust-lang/compiler-team#724, based on data gathered in #119440.
This commit is contained in:
bors 2024-04-13 17:18:42 +00:00
commit af6a1613b3
6 changed files with 109 additions and 27 deletions
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8
compiler/rustc_span/src/span_encoding.rs
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@ -5,6 +5,10 @@ use crate::{BytePos, SpanData};
use rustc_data_structures::fx::FxIndexSet;
// This code is very hot and uses lots of arithmetic, avoid overflow checks for performance.
// See https://github.com/rust-lang/rust/pull/119440#issuecomment-1874255727
use rustc_serialize::int_overflow::DebugStrictAdd;
/// A compressed span.
///
/// [`SpanData`] is 16 bytes, which is too big to stick everywhere. `Span` only
@ -166,7 +170,7 @@ impl Span {
debug_assert!(len <= MAX_LEN);
SpanData {
lo: BytePos(self.lo_or_index),
hi: BytePos(self.lo_or_index + len),
hi: BytePos(self.lo_or_index.debug_strict_add(len)),
ctxt: SyntaxContext::from_u32(self.ctxt_or_parent_or_marker as u32),
parent: None,
}
@ -179,7 +183,7 @@ impl Span {
};
SpanData {
lo: BytePos(self.lo_or_index),
hi: BytePos(self.lo_or_index + len),
hi: BytePos(self.lo_or_index.debug_strict_add(len)),
ctxt: SyntaxContext::root(),
parent: Some(parent),
}