From 11d22ae7c572ce35923ced63415e95f0a2ab8361 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Mon, 30 May 2022 15:59:45 +1000
Subject: [PATCH] Lazify `SourceFile::lines`.
`SourceFile::lines` is a big part of metadata. It's stored in a compressed form
(a difference list) to save disk space. Decoding it is a big fraction of
compile time for very small crates/programs.
This commit introduces a new type `SourceFileLines` which has a `Lines`
form and a `Diffs` form. The latter is used when the metadata is first
read, and it is only decoded into the `Lines` form when line data is
actually needed. This avoids the decoding cost for many files,
especially in `std`. It's a performance win of up to 15% for tiny
crates/programs where metadata decoding is a high part of compilation
costs.
A `Lock` is needed because the methods that access lines data (which can
trigger decoding) take `&self` rather than `&mut self`. To allow for this,
`SourceFile::lines` now takes a `FnMut` that operates on the lines slice rather
than returning the lines slice.
---
.../src/undocumented_unsafe_blocks.rs | 36 +++++++++++--------
clippy_utils/src/diagnostics.rs | 4 +--
clippy_utils/src/lib.rs | 2 +-
3 files changed, 24 insertions(+), 18 deletions(-)
diff --git a/clippy_lints/src/undocumented_unsafe_blocks.rs b/clippy_lints/src/undocumented_unsafe_blocks.rs
index 5a8677f90be..025dd57e83a 100644
--- a/clippy_lints/src/undocumented_unsafe_blocks.rs
+++ b/clippy_lints/src/undocumented_unsafe_blocks.rs
@@ -187,11 +187,13 @@ fn item_has_safety_comment(cx: &LateContext<'_>, item: &hir::Item<'_>) -> bool {
&& Lrc::ptr_eq(&unsafe_line.sf, &comment_start_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
{
- comment_start_line.line < unsafe_line.line && text_has_safety_comment(
- src,
- &unsafe_line.sf.lines[comment_start_line.line + 1..=unsafe_line.line],
- unsafe_line.sf.start_pos.to_usize(),
- )
+ unsafe_line.sf.lines(|lines| {
+ comment_start_line.line < unsafe_line.line && text_has_safety_comment(
+ src,
+ &lines[comment_start_line.line + 1..=unsafe_line.line],
+ unsafe_line.sf.start_pos.to_usize(),
+ )
+ })
} else {
// Problem getting source text. Pretend a comment was found.
true
@@ -249,11 +251,13 @@ fn span_from_macro_expansion_has_safety_comment(cx: &LateContext<'_>, span: Span
&& Lrc::ptr_eq(&unsafe_line.sf, ¯o_line.sf)
&& let Some(src) = unsafe_line.sf.src.as_deref()
{
- macro_line.line < unsafe_line.line && text_has_safety_comment(
- src,
- &unsafe_line.sf.lines[macro_line.line + 1..=unsafe_line.line],
- unsafe_line.sf.start_pos.to_usize(),
- )
+ unsafe_line.sf.lines(|lines| {
+ macro_line.line < unsafe_line.line && text_has_safety_comment(
+ src,
+ &lines[macro_line.line + 1..=unsafe_line.line],
+ unsafe_line.sf.start_pos.to_usize(),
+ )
+ })
} else {
// Problem getting source text. Pretend a comment was found.
true
@@ -276,11 +280,13 @@ fn span_in_body_has_safety_comment(cx: &LateContext<'_>, span: Span) -> bool {
// Get the text from the start of function body to the unsafe block.
// fn foo() { some_stuff; unsafe { stuff }; other_stuff; }
// ^-------------^
- body_line.line < unsafe_line.line && text_has_safety_comment(
- src,
- &unsafe_line.sf.lines[body_line.line + 1..=unsafe_line.line],
- unsafe_line.sf.start_pos.to_usize(),
- )
+ unsafe_line.sf.lines(|lines| {
+ body_line.line < unsafe_line.line && text_has_safety_comment(
+ src,
+ &lines[body_line.line + 1..=unsafe_line.line],
+ unsafe_line.sf.start_pos.to_usize(),
+ )
+ })
} else {
// Problem getting source text. Pretend a comment was found.
true
diff --git a/clippy_utils/src/diagnostics.rs b/clippy_utils/src/diagnostics.rs
index 4e037d88494..39595f589c7 100644
--- a/clippy_utils/src/diagnostics.rs
+++ b/clippy_utils/src/diagnostics.rs
@@ -283,10 +283,10 @@ pub fn span_lint_and_sugg_for_edges(
{
let split_idx = MAX_SUGGESTION_HIGHLIGHT_LINES / 2;
let span_upper = sm.span_until_char(
- sp.with_hi(line_upper.sf.lines[line_upper.line + split_idx]),
+ sp.with_hi(line_upper.sf.lines(|lines| lines[line_upper.line + split_idx])),
'\n',
);
- let span_bottom = sp.with_lo(line_bottom.sf.lines[line_bottom.line - split_idx]);
+ let span_bottom = sp.with_lo(line_bottom.sf.lines(|lines| lines[line_bottom.line - split_idx]));
let sugg_lines_vec = sugg.lines().collect::<Vec<&str>>();
let sugg_upper = sugg_lines_vec[..split_idx].join("\n");
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index adb37cc9d75..833f8cde63a 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -1149,7 +1149,7 @@ fn line_span<T: LintContext>(cx: &T, span: Span) -> Span {
let span = original_sp(span, DUMMY_SP);
let source_map_and_line = cx.sess().source_map().lookup_line(span.lo()).unwrap();
let line_no = source_map_and_line.line;
- let line_start = source_map_and_line.sf.lines[line_no];
+ let line_start = source_map_and_line.sf.lines(|lines| lines[line_no]);
span.with_lo(line_start)
}