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_posts/2024-11-27-newsletter-firefox-132-134.md

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+---
+layout: post
+title:  "SpiderMonkey Newsletter (Firefox 132-134)"
+date:   2024-11-27 18:00:00 +0100
+author: Matthew Gaudet
+---
+
+Hello! Welcome to another episode of the SpiderMonkey Newsletter. I’m your host,
+Matthew Gaudet.
+
+In the spirit of the [upcoming
+season](https://en.wikipedia.org/wiki/Thanksgiving_\(United_States\)), let’s [talk
+turkey](https://en.wiktionary.org/wiki/talk_turkey). I mean, monkeys. I mean
+SpiderMonkey.
+
+Today we’ll cover a little more ground than the normal newsletter.
+
+If you haven’t already read Jan’s wonderful blog about how he managed to improve Wasm
+compilation speed by 75x on large modules, [please take a
+peek](https://spidermonkey.dev/blog/2024/10/16/75x-faster-optimizing-the-ion-compiler-backend.html).
+It’s a great story of how O(n^2) is the worst complexity – fast enough to seem OK in
+small cases, and slow enough to blow up horrendously when things get big.
+
+### 🚀 Performance
+
+- Awesome contributor Debadree [has added IC support for addition and subtraction on
+  Date Objects](https://bugzilla.mozilla.org/show_bug.cgi?id=1490441)
+
+- Jan [worked on saving fewer registers when calling out to C++
+  code](https://bugzilla.mozilla.org/show_bug.cgi?id=1919217), providing a 5%
+  improvement on some speedometer subtests.
+
+- Jon [improved the performance of store buffer
+  iteration](https://bugzilla.mozilla.org/show_bug.cgi?id=1920761) by avoiding
+  linked-list traversal where possible.
+
+- Jon [improved the performance of
+  sweeping](https://bugzilla.mozilla.org/show_bug.cgi?id=1925581) by doing more work
+  without holding a lock
+
+- Jan [continued improving register allocation by choosing a better representation
+  for sparse bitsets](http://bugzilla.mozilla.org/show_bug.cgi?id=1920430), improving
+  compilation time on a wasm module by 40%, and improving some PDF test cases by 5%.
+
+- Jan worked on [Map and Set
+  Optimizations,](https://bugzilla.mozilla.org/show_bug.cgi?id=1851662) with
+  improvements across a number of benchmarks.
+
+### 👷🏽‍♀️ New features & In Progress Standards Work
+
+- The WebAssembly Memory64 proposal has reached stage 4 and is enabled by default in
+  Firefox 134. This proposal finally adds 64-bit pointers to WebAssembly—although
+  this comes with some downsides, so stay tuned for a blog post exploring this
+  subject further.
+
+- Prolific contributor André has worked on over 30 (‼) bugs in this newsletter time
+  frame. Feature wise he’s continued his incredible stewardship of the Temporal
+  proposal, as well as [implementing Int.Duration
+  format](https://bugzilla.mozilla.org/show_bug.cgi?id=1648139), providing [initial
+  implementation of
+  Atomics.pause](https://bugzilla.mozilla.org/show_bug.cgi?id=1930952).
+
+- Speaking of great contributors: Debadree has continued work on the [Explicit
+  Resource Management
+  proposal](https://github.com/tc39/proposal-explicit-resource-management), with [the
+  implementation looking like it’s in great
+  shape](https://bugzilla.mozilla.org/show_bug.cgi?id=1569081).
+
+- Dan has been on a roll shipping proposals:
+  [Promise.try](https://bugzilla.mozilla.org/show_bug.cgi?id=1918235),
+  [Regexp.escape](https://bugzilla.mozilla.org/show_bug.cgi?id=1918235), and [Regular
+  Expression Pattern
+  Modifiers](https://bugzilla.mozilla.org/show_bug.cgi?id=1913752).
+
+### **🚉** SpiderMonkey Platform Improvements
+
+- Jan has killed a whole class of errors that have [bedevilled SpiderMonkey
+  developers for at least 15
+  years.](https://bugzilla.mozilla.org/show_bug.cgi?id=552007) The root cause of the
+  issue is the overloading of error checking inside of SpiderMonkey. The general case
+  is “Report an Exception” and return false.
+
+  The problem is that, returning false without setting an exception \-also- has a
+  meaning: It’s throwing an uncatchable exception, which is used for things like
+  unwinding when you stop a script due to the slow script dialog.
+
+  So what happens if you were to accidentally return false without setting an
+  exception: Did you mean to do that? Or did you forget? In [Bug
+  1921215](https://bugzilla.mozilla.org/show_bug.cgi?id=1921215), [bug
+  1921780](https://bugzilla.mozilla.org/show_bug.cgi?id=1921780), and [bug
+  1921963](https://bugzilla.mozilla.org/show_bug.cgi?id=1921963) Jan has tidied this
+  whole story up with a new helper `JS::ReportUncatchableException` and assertions
+  that validate you’ve used this correctly!
+
+- Debadree [added support for generating LIR ops where they are pretty
+  straightforward boilerplate](https://bugzilla.mozilla.org/show_bug.cgi?id=1916359).
+  This will reduce the amount of work we have to do when improving the JITs. Previous
+  work like this has been appreciated hugely, and I expect we’ll find lots of value
+  in this quickly.
+
+- Denis [has made `--enable-perf` the default for nightly
+  builds](https://bugzilla.mozilla.org/show_bug.cgi?id=1918139), which will make
+  profiling Firefox more effective.
+
+- A few years ago our OS integration team deployed a neat trick on Windows to reduce
+  out of memory errors in Firefox, [written up in this wonderful blog
+  post](https://hacks.mozilla.org/2022/11/improving-firefox-stability-with-this-one-weird-trick/).
+  Recently [Jon went through the effort to apply this same weird trick to our own
+  memory allocation](https://bugzilla.mozilla.org/show_bug.cgi?id=1786451). Our hope
+  is that this will reduce the amount of out-of-memory failures.
+