mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Simplify encoding a bit.

Browse Source
This commit is contained in:
Camille GILLOT 2022-08-06 23:13:09 +02:00
parent d74af405eb
commit 7c2d722fb0
1 changed files with 35 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
compiler/rustc_metadata/src/rmeta/encoder.rs
View File

@ -234,13 +234,17 @@ fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
s.source_file_cache =
(source_map.files()[source_file_index].clone(), source_file_index);
}
let (ref source_file, source_file_index) = s.source_file_cache;
if !s.source_file_cache.0.contains(span.hi) {
if !source_file.contains(span.hi) {
// Unfortunately, macro expansion still sometimes generates Spans
// that malformed in this way.
return TAG_PARTIAL_SPAN.encode(s);
}
// Length is independent of the span provenance.
let len = span.hi - span.lo;
// There are two possible cases here:
// 1. This span comes from a 'foreign' crate - e.g. some crate upstream of the
// crate we are writing metadata for. When the metadata for *this* crate gets
@ -257,47 +261,44 @@ fn encode(&self, s: &mut EncodeContext<'a, 'tcx>) {
// if we're a proc-macro crate.
// This allows us to avoid loading the dependencies of proc-macro crates: all of
// the information we need to decode `Span`s is stored in the proc-macro crate.
let (tag, lo, hi, metadata_index) =
if s.source_file_cache.0.is_imported() && !s.is_proc_macro {
// To simplify deserialization, we 'rebase' this span onto the crate it originally came from
// (the crate that 'owns' the file it references. These rebased 'lo' and 'hi' values
// are relative to the source map information for the 'foreign' crate whose CrateNum
// we write into the metadata. This allows `imported_source_files` to binary
// search through the 'foreign' crate's source map information, using the
// deserialized 'lo' and 'hi' values directly.
//
// All of this logic ensures that the final result of deserialization is a 'normal'
// Span that can be used without any additional trouble.
let (external_start_pos, metadata_index) = {
// Introduce a new scope so that we drop the 'lock()' temporary
match &*s.source_file_cache.0.external_src.lock() {
ExternalSource::Foreign { original_start_pos, metadata_index, .. } => {
(*original_start_pos, *metadata_index)
}
src => panic!("Unexpected external source {:?}", src),
let (tag, lo, metadata_index) = if source_file.is_imported() && !s.is_proc_macro {
// To simplify deserialization, we 'rebase' this span onto the crate it originally came from
// (the crate that 'owns' the file it references. These rebased 'lo' and 'hi' values
// are relative to the source map information for the 'foreign' crate whose CrateNum
// we write into the metadata. This allows `imported_source_files` to binary
// search through the 'foreign' crate's source map information, using the
// deserialized 'lo' and 'hi' values directly.
//
// All of this logic ensures that the final result of deserialization is a 'normal'
// Span that can be used without any additional trouble.
let (external_start_pos, metadata_index) = {
// Introduce a new scope so that we drop the 'lock()' temporary
match &*source_file.external_src.lock() {
ExternalSource::Foreign { original_start_pos, metadata_index, .. } => {
(*original_start_pos, *metadata_index)
}
};
let lo = (span.lo - s.source_file_cache.0.start_pos) + external_start_pos;
let hi = (span.hi - s.source_file_cache.0.start_pos) + external_start_pos;
(TAG_VALID_SPAN_FOREIGN, lo, hi, metadata_index)
} else {
// Record the fact that we need to encode the data for this `SourceFile`
let source_files =
s.required_source_files.as_mut().expect("Already encoded SourceMap!");
let (source_file_index, _) = source_files.insert_full(s.source_file_cache.1);
let source_file_index: u32 =
source_file_index.try_into().expect("cannot export more than U32_MAX files");
(TAG_VALID_SPAN_LOCAL, span.lo, span.hi, source_file_index)
src => panic!("Unexpected external source {:?}", src),
}
};
let lo = (span.lo - source_file.start_pos) + external_start_pos;
(TAG_VALID_SPAN_FOREIGN, lo, metadata_index)
} else {
// Record the fact that we need to encode the data for this `SourceFile`
let source_files =
s.required_source_files.as_mut().expect("Already encoded SourceMap!");
let (metadata_index, _) = source_files.insert_full(source_file_index);
let metadata_index: u32 =
metadata_index.try_into().expect("cannot export more than U32_MAX files");
(TAG_VALID_SPAN_LOCAL, span.lo, metadata_index)
};
tag.encode(s);
lo.encode(s);
// Encode length which is usually less than span.hi and profits more
// from the variable-length integer encoding that we use.
let len = hi - lo;
len.encode(s);
// Encode the index of the `SourceFile` for the span, in order to make decoding faster.