diff options
Diffstat (limited to 'compiler/rustc_span/src/span_encoding.rs')
| -rw-r--r-- | compiler/rustc_span/src/span_encoding.rs | 86 |
1 files changed, 64 insertions, 22 deletions
diff --git a/compiler/rustc_span/src/span_encoding.rs b/compiler/rustc_span/src/span_encoding.rs index f0e91e5a6..d48c4f7e5 100644 --- a/compiler/rustc_span/src/span_encoding.rs +++ b/compiler/rustc_span/src/span_encoding.rs @@ -4,7 +4,7 @@ // The encoding format for inline spans were obtained by optimizing over crates in rustc/libstd. // See https://internals.rust-lang.org/t/rfc-compiler-refactoring-spans/1357/28 -use crate::def_id::LocalDefId; +use crate::def_id::{DefIndex, LocalDefId}; use crate::hygiene::SyntaxContext; use crate::SPAN_TRACK; use crate::{BytePos, SpanData}; @@ -13,8 +13,8 @@ use rustc_data_structures::fx::FxIndexSet; /// A compressed span. /// -/// Whereas [`SpanData`] is 12 bytes, which is a bit too big to stick everywhere, `Span` -/// is a form that only takes up 8 bytes, with less space for the length and +/// Whereas [`SpanData`] is 16 bytes, which is a bit too big to stick everywhere, `Span` +/// is a form that only takes up 8 bytes, with less space for the length, parent and /// context. The vast majority (99.9%+) of `SpanData` instances will fit within /// those 8 bytes; any `SpanData` whose fields don't fit into a `Span` are /// stored in a separate interner table, and the `Span` will index into that @@ -25,7 +25,7 @@ use rustc_data_structures::fx::FxIndexSet; /// slower because only 80--90% of spans could be stored inline (even less in /// very large crates) and so the interner was used a lot more. /// -/// Inline (compressed) format: +/// Inline (compressed) format with no parent: /// - `span.base_or_index == span_data.lo` /// - `span.len_or_tag == len == span_data.hi - span_data.lo` (must be `<= MAX_LEN`) /// - `span.ctxt_or_tag == span_data.ctxt` (must be `<= MAX_CTXT`) @@ -35,6 +35,12 @@ use rustc_data_structures::fx::FxIndexSet; /// - `span.len_or_tag == LEN_TAG` (high bit set, all other bits are zero) /// - `span.ctxt_or_tag == span_data.ctxt` (must be `<= MAX_CTXT`) /// +/// Inline (compressed) format with root context: +/// - `span.base_or_index == span_data.lo` +/// - `span.len_or_tag == len == span_data.hi - span_data.lo` (must be `<= MAX_LEN`) +/// - `span.len_or_tag` has top bit (`PARENT_MASK`) set +/// - `span.ctxt == span_data.parent` (must be `<= MAX_CTXT`) +/// /// Interned format: /// - `span.base_or_index == index` (indexes into the interner table) /// - `span.len_or_tag == LEN_TAG` (high bit set, all other bits are zero) @@ -73,7 +79,8 @@ pub struct Span { ctxt_or_tag: u16, } -const LEN_TAG: u16 = 0b1000_0000_0000_0000; +const LEN_TAG: u16 = 0b1111_1111_1111_1111; +const PARENT_MASK: u16 = 0b1000_0000_0000_0000; const MAX_LEN: u32 = 0b0111_1111_1111_1111; const CTXT_TAG: u32 = 0b1111_1111_1111_1111; const MAX_CTXT: u32 = CTXT_TAG - 1; @@ -95,16 +102,32 @@ impl Span { let (base, len, ctxt2) = (lo.0, hi.0 - lo.0, ctxt.as_u32()); - if len <= MAX_LEN && ctxt2 <= MAX_CTXT && parent.is_none() { - // Inline format. - Span { base_or_index: base, len_or_tag: len as u16, ctxt_or_tag: ctxt2 as u16 } - } else { - // Interned format. - let index = - with_span_interner(|interner| interner.intern(&SpanData { lo, hi, ctxt, parent })); - let ctxt_or_tag = if ctxt2 <= MAX_CTXT { ctxt2 } else { CTXT_TAG } as u16; - Span { base_or_index: index, len_or_tag: LEN_TAG, ctxt_or_tag } + if len <= MAX_LEN && ctxt2 <= MAX_CTXT { + let len_or_tag = len as u16; + debug_assert_eq!(len_or_tag & PARENT_MASK, 0); + + if let Some(parent) = parent { + // Inline format with parent. + let len_or_tag = len_or_tag | PARENT_MASK; + let parent2 = parent.local_def_index.as_u32(); + if ctxt2 == SyntaxContext::root().as_u32() && parent2 <= MAX_CTXT { + return Span { base_or_index: base, len_or_tag, ctxt_or_tag: parent2 as u16 }; + } + } else { + // Inline format with ctxt. + return Span { + base_or_index: base, + len_or_tag: len as u16, + ctxt_or_tag: ctxt2 as u16, + }; + } } + + // Interned format. + let index = + with_span_interner(|interner| interner.intern(&SpanData { lo, hi, ctxt, parent })); + let ctxt_or_tag = if ctxt2 <= MAX_CTXT { ctxt2 } else { CTXT_TAG } as u16; + Span { base_or_index: index, len_or_tag: LEN_TAG, ctxt_or_tag } } #[inline] @@ -122,12 +145,25 @@ impl Span { pub fn data_untracked(self) -> SpanData { if self.len_or_tag != LEN_TAG { // Inline format. - debug_assert!(self.len_or_tag as u32 <= MAX_LEN); - SpanData { - lo: BytePos(self.base_or_index), - hi: BytePos(self.base_or_index + self.len_or_tag as u32), - ctxt: SyntaxContext::from_u32(self.ctxt_or_tag as u32), - parent: None, + if self.len_or_tag & PARENT_MASK == 0 { + debug_assert!(self.len_or_tag as u32 <= MAX_LEN); + SpanData { + lo: BytePos(self.base_or_index), + hi: BytePos(self.base_or_index + self.len_or_tag as u32), + ctxt: SyntaxContext::from_u32(self.ctxt_or_tag as u32), + parent: None, + } + } else { + let len = self.len_or_tag & !PARENT_MASK; + debug_assert!(len as u32 <= MAX_LEN); + let parent = + LocalDefId { local_def_index: DefIndex::from_u32(self.ctxt_or_tag as u32) }; + SpanData { + lo: BytePos(self.base_or_index), + hi: BytePos(self.base_or_index + len as u32), + ctxt: SyntaxContext::root(), + parent: Some(parent), + } } } else { // Interned format. @@ -141,8 +177,14 @@ impl Span { pub fn ctxt(self) -> SyntaxContext { let ctxt_or_tag = self.ctxt_or_tag as u32; if ctxt_or_tag <= MAX_CTXT { - // Inline format or interned format with inline ctxt. - SyntaxContext::from_u32(ctxt_or_tag) + if self.len_or_tag == LEN_TAG || self.len_or_tag & PARENT_MASK == 0 { + // Inline format or interned format with inline ctxt. + SyntaxContext::from_u32(ctxt_or_tag) + } else { + // Inline format or interned format with inline parent. + // We know that the SyntaxContext is root. + SyntaxContext::root() + } } else { // Interned format. let index = self.base_or_index; |