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LibJS: Make line-and-column resolution fast for large minified JS

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Instead of caching start-of-line offsets, we now cache byte offsets
at regular intervals. This fixes an issue where we had terrible
performance on large minified JS, since that often means one very,
VERY long line (with no line endings to cache).

My machine was spending ~35ms per stack frame when throwing errors
on some heavy minified websites, and after this patch, we now spend
<1ms per stack frame.
This commit is contained in:
Andreas Kling 2023-09-12 13:03:56 +02:00
parent ff02de4ad0
commit 44b2735b9e
4 changed files with 67 additions and 35 deletions
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7
Userland/Libraries/LibJS/SourceRange.h
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@ -10,16 +10,11 @@
#include <AK/NonnullRefPtr.h>
#include <AK/StringView.h>
#include <AK/Types.h>
#include <LibJS/Position.h>
#include <LibJS/SourceCode.h>
namespace JS {
struct Position {
size_t line { 0 };
size_t column { 0 };
size_t offset { 0 };
};
struct SourceRange {
[[nodiscard]] bool contains(Position const& position) const { return position.offset <= end.offset && position.offset >= start.offset; }