Rollup merge of #147189 - yotamofek:pr/rustdoc/highlight-optimizations-2, r=GuillaumeGomez

Replace `rustc_span::Span` with a stripped down version for librustdoc's highlighter

While profiling rustdoc's syntax highlighter, I noticed a lot of time being spent in the `Span` interner, due to the highlighter creating a lot of (new) spans.
Since the only data from the `Span` that we use is the `hi` and `lo` byte positions - I replaced the regular `Span` with a simple one with two fields, and in my benchmarks it seemed to make a big dent in the highlighter's perf, so thought I would see what the perf runner says.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/librustdoc/html/highlight.rs b/src/librustdoc/html/highlight.rs
index fad15573cde..1dcb4dcc3ff 100644
--- a/src/librustdoc/html/highlight.rs
+++ b/src/librustdoc/html/highlight.rs
@@ -12,15 +12,16 @@ use std::iter;
 
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_lexer::{Cursor, FrontmatterAllowed, LiteralKind, TokenKind};
+use rustc_span::BytePos;
 use rustc_span::edition::Edition;
 use rustc_span::symbol::Symbol;
-use rustc_span::{BytePos, DUMMY_SP, Span};
 
 use super::format;
 use crate::clean::PrimitiveType;
 use crate::display::Joined as _;
 use crate::html::escape::EscapeBodyText;
 use crate::html::macro_expansion::ExpandedCode;
+use crate::html::render::span_map::{DUMMY_SP, Span};
 use crate::html::render::{Context, LinkFromSrc};
 
 /// This type is needed in case we want to render links on items to allow to go to their definition.