SSE2 is always available in 64bit CPUs, it's included in the AMD64
specification.
So I'd be surprised if compilers didn't automatically use SSE2 for 64bit
targets.
Another interesting data point is that Windows 8.1 doesn't work without
SSE2 [1],
but I guess most people that use Windows 8.1 have a 64bit CPU.
[1] http://windows.microsoft.com/en-GB/windows-8/what-is-pae-nx-sse2
- Marco.
Il 01/02/16 15:00, Xidorn Quan ha scritto:
On Tue, Feb 2, 2016 at 7:04 AM, Benjamin Smedberg <benja...@smedbergs.us> wrote:
On 1/29/2016 2:05 PM, Cameron Kaiser wrote:
On 1/29/16 9:43 AM, Ashley Gullen wrote:
FWIW, the Steam Hardware Survey says 99.99% of users have SSE2 (under
"other settings"): http://store.steampowered.com/hwsurvey
For that to be valid, one must assume that the population of Firefox users
and Steam users are sufficiently similar. I don't think that's necessarily
true since most Steam titles have substantially higher system requirements.
The last time we broke this (by accident) was several years ago. At the
time, we got vigorous complaining from various people who had relatively
recent bare-bones machines without SSE2.
It might be worth reconsidering now: I'm not willing to throw away 0.5% of
our users without good cause, but perhaps there is a good cause to be made
here? What would the performance gain be for the remaining 99.5% of users,
realizing that we already have dynamic SSE2/non-SSE switching in place for
some of our hottest paths.
The main question here I think is, whether we've enabled SSE2 for 64bit build
It seems to me if we do, whether enabling SSE2 on x86 doesn't really
matter unless we have a good reason. Fewer and fewer people would
stick on x86, especially who cares about performance.
If we haven't yet done that, we should. It seems to me the majority
processors which supports x64 also supports SSE2. If there are really
some people who use a processor doesn't support SSE2 but are using
64bit Firefox, they could simply back to use the 32bit version.
- Xidorn
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