Joshua Cranmer 🐧 Pidgeot18 at
Fri Jul 11 16:31:13 UTC 2014

On 7/11/2014 11:20 AM, Patrick Cloke wrote:
> Looking over posts on the forum  a bit it seems to be pretty much
 > Thunderbird:
 > "Fossamail comes
 > with different defaults (both UI and under-the-hood) and has been
 > rebuilt with a newer compiler and better optimizations than
 > Thunderbird. Otherwise, there aren't many differences. At least not
 > at this time."
 > pretty much talks
 > in circles that it's "optimized" but won't say how.

My recollection is that "optimized" in this builds usually means:
* Use a different, newer compiler (maybe even ICC?)
* 64-bit builds instead of 32-bit builds
* Tuning options for relatively newer ISAs (e.g., SSE3 or SSSE3, etc.)

At least one the first one of these "optimized" rebuilds of Firefox came 
out, it was very much well-known within Firefox that our 64-bit JIT 
sucked more than the 32-bit JIT, which made the "optimized" claim fairly 

My personal take on this sort of "optimization" is that it's performance 
tuning by people who know nothing about performance tuning and are just 
parroting effectively marketing material without understanding it: amd64 
isn't necessarily faster than ia32 (especially since increased pointer 
sizes stress caches a lot more), and excessive flag combinations on your 
builds can very easily slow your builds down because you lost the 
lottery. Seeing as how we don't have any performance metrics, and I'm 
willing to bet whoever built this didn't try to come up with one [let 
alone create one that actually carries validity--not an easy task even 
if you're an expert], I'm very skeptical that there's anything actually 
useful here.

Joshua Cranmer
Thunderbird and DXR developer
Source code archæologist

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