Hash all spans relatively to their parent

Co-authored-by: Camille Gillot <gillot.camille@gmail.com>

Author: JonathanBrouwer

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -20,8 +20,8 @@ use rustc_span::hygiene::{
 };
 use rustc_span::source_map::Spanned;
 use rustc_span::{
-    BlobDecoder, BytePos, ByteSymbol, CachingSourceMapView, ExpnData, ExpnHash, Pos,
-    RelativeBytePos, SourceFile, Span, SpanDecoder, SpanEncoder, StableSourceFileId, Symbol,
+    BlobDecoder, BytePos, ByteSymbol, CachingSourceMapView, ExpnData, ExpnHash, RelativeBytePos,
+    SourceFile, Span, SpanDecoder, SpanEncoder, StableSourceFileId, Symbol,
 };
 
 use crate::dep_graph::{DepNodeIndex, SerializedDepNodeIndex};
@@ -652,7 +652,10 @@ impl<'a, 'tcx> SpanDecoder for CacheDecoder<'a, 'tcx> {
                 let dto = u32::decode(self);
 
                 let enclosing = self.tcx.source_span_untracked(parent.unwrap()).data_untracked();
-                (enclosing.lo + BytePos::from_u32(dlo), enclosing.lo + BytePos::from_u32(dto))
+                (
+                    BytePos(enclosing.lo.0.wrapping_add(dlo)),
+                    BytePos(enclosing.lo.0.wrapping_add(dto)),
+                )
             }
             TAG_FULL_SPAN => {
                 let file_lo_index = SourceFileIndex::decode(self);
@@ -894,30 +897,33 @@ impl<'a, 'tcx> SpanEncoder for CacheEncoder<'a, 'tcx> {
             return TAG_PARTIAL_SPAN.encode(self);
         }
 
-        if let Some(parent) = span_data.parent {
-            let enclosing = self.tcx.source_span_untracked(parent).data_untracked();
-            if enclosing.contains(span_data) {
-                TAG_RELATIVE_SPAN.encode(self);
-                (span_data.lo - enclosing.lo).to_u32().encode(self);
-                (span_data.hi - enclosing.lo).to_u32().encode(self);
-                return;
-            }
+        let parent =
+            span_data.parent.map(|parent| self.tcx.source_span_untracked(parent).data_untracked());
+        if let Some(parent) = parent
+            && parent.contains(span_data)
+        {
+            TAG_RELATIVE_SPAN.encode(self);
+            (span_data.lo.0.wrapping_sub(parent.lo.0)).encode(self);
+            (span_data.hi.0.wrapping_sub(parent.lo.0)).encode(self);
+            return;
         }
 
-        let pos = self.source_map.byte_pos_to_line_and_col(span_data.lo);
-        let partial_span = match &pos {
-            Some((file_lo, _, _)) => !file_lo.contains(span_data.hi),
-            None => true,
+        let Some((file_lo, line_lo, col_lo)) =
+            self.source_map.byte_pos_to_line_and_col(span_data.lo)
+        else {
+            return TAG_PARTIAL_SPAN.encode(self);
         };
 
-        if partial_span {
-            return TAG_PARTIAL_SPAN.encode(self);
+        if let Some(parent) = parent
+            && file_lo.contains(parent.lo)
+        {
+            TAG_RELATIVE_SPAN.encode(self);
+            (span_data.lo.0.wrapping_sub(parent.lo.0)).encode(self);
+            (span_data.hi.0.wrapping_sub(parent.lo.0)).encode(self);
+            return;
         }
 
-        let (file_lo, line_lo, col_lo) = pos.unwrap();
-
         let len = span_data.hi - span_data.lo;
-
         let source_file_index = self.source_file_index(file_lo);
 
         TAG_FULL_SPAN.encode(self);

compiler/rustc_query_system/src/ich/hcx.rs

@@ -5,9 +5,7 @@ use rustc_hir::definitions::DefPathHash;
 use rustc_session::Session;
 use rustc_session::cstore::Untracked;
 use rustc_span::source_map::SourceMap;
-use rustc_span::{
-    BytePos, CachingSourceMapView, DUMMY_SP, Span, SpanData, StableSourceFileId, Symbol,
-};
+use rustc_span::{BytePos, CachingSourceMapView, DUMMY_SP, SourceFile, Span, SpanData, Symbol};
 
 use crate::ich;
 
@@ -118,7 +116,7 @@ impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
     fn span_data_to_lines_and_cols(
         &mut self,
         span: &SpanData,
-    ) -> Option<(StableSourceFileId, usize, BytePos, usize, BytePos)> {
+    ) -> Option<(&SourceFile, usize, BytePos, usize, BytePos)> {
         self.source_map().span_data_to_lines_and_cols(span)
     }
 

compiler/rustc_span/src/caching_source_map_view.rs

@@ -2,7 +2,7 @@ use std::ops::Range;
 use std::sync::Arc;
 
 use crate::source_map::SourceMap;
-use crate::{BytePos, Pos, RelativeBytePos, SourceFile, SpanData, StableSourceFileId};
+use crate::{BytePos, Pos, RelativeBytePos, SourceFile, SpanData};
 
 #[derive(Clone)]
 struct CacheEntry {
@@ -114,7 +114,7 @@ impl<'sm> CachingSourceMapView<'sm> {
     pub fn span_data_to_lines_and_cols(
         &mut self,
         span_data: &SpanData,
-    ) -> Option<(StableSourceFileId, usize, BytePos, usize, BytePos)> {
+    ) -> Option<(&SourceFile, usize, BytePos, usize, BytePos)> {
         self.time_stamp += 1;
 
         // Check if lo and hi are in the cached lines.
@@ -136,7 +136,7 @@ impl<'sm> CachingSourceMapView<'sm> {
             let lo = &self.line_cache[lo_cache_idx as usize];
             let hi = &self.line_cache[hi_cache_idx as usize];
             return Some((
-                lo.file.stable_id,
+                &lo.file,
                 lo.line_number,
                 span_data.lo - lo.line.start,
                 hi.line_number,
@@ -224,7 +224,7 @@ impl<'sm> CachingSourceMapView<'sm> {
         assert_eq!(lo.file_index, hi.file_index);
 
         Some((
-            lo.file.stable_id,
+            &lo.file,
             lo.line_number,
             span_data.lo - lo.line.start,
             hi.line_number,

compiler/rustc_span/src/lib.rs

@@ -2831,7 +2831,7 @@ pub trait HashStableContext {
     fn span_data_to_lines_and_cols(
         &mut self,
         span: &SpanData,
-    ) -> Option<(StableSourceFileId, usize, BytePos, usize, BytePos)>;
+    ) -> Option<(&SourceFile, usize, BytePos, usize, BytePos)>;
     fn hashing_controls(&self) -> HashingControls;
 }
 
@@ -2849,6 +2849,8 @@ where
     /// codepoint offsets. For the purpose of the hash that's sufficient.
     /// Also, hashing filenames is expensive so we avoid doing it twice when the
     /// span starts and ends in the same file, which is almost always the case.
+    ///
+    /// IMPORTANT: changes to this method should be reflected in implementations of `SpanEncoder`.
     fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
         const TAG_VALID_SPAN: u8 = 0;
         const TAG_INVALID_SPAN: u8 = 1;
@@ -2867,15 +2869,16 @@ where
             return;
         }
 
-        if let Some(parent) = span.parent {
-            let def_span = ctx.def_span(parent).data_untracked();
-            if def_span.contains(span) {
-                // This span is enclosed in a definition: only hash the relative position.
-                Hash::hash(&TAG_RELATIVE_SPAN, hasher);
-                (span.lo - def_span.lo).to_u32().hash_stable(ctx, hasher);
-                (span.hi - def_span.lo).to_u32().hash_stable(ctx, hasher);
-                return;
-            }
+        let parent = span.parent.map(|parent| ctx.def_span(parent).data_untracked());
+        if let Some(parent) = parent
+            && parent.contains(span)
+        {
+            // This span is enclosed in a definition: only hash the relative position.
+            // The "in the same file" check below
+            Hash::hash(&TAG_RELATIVE_SPAN, hasher);
+            (span.lo - parent.lo).to_u32().hash_stable(ctx, hasher);
+            (span.hi - parent.lo).to_u32().hash_stable(ctx, hasher);
+            return;
         }
 
         // If this is not an empty or invalid span, we want to hash the last
@@ -2887,8 +2890,19 @@ where
             return;
         };
 
+        if let Some(parent) = parent
+            && file.contains(parent.lo)
+        {
+            // This span is relative to another span in the same file,
+            // only hash the relative position.
+            Hash::hash(&TAG_RELATIVE_SPAN, hasher);
+            Hash::hash(&(span.lo.0.wrapping_sub(parent.lo.0)), hasher);
+            Hash::hash(&(span.hi.0.wrapping_sub(parent.lo.0)), hasher);
+            return;
+        }
+
         Hash::hash(&TAG_VALID_SPAN, hasher);
-        Hash::hash(&file, hasher);
+        Hash::hash(&file.stable_id, hasher);
 
         // Hash both the length and the end location (line/column) of a span. If we
         // hash only the length, for example, then two otherwise equal spans with