1265366 - Option to turn on SSE2 autovectorization and SSE2-based floating-point math on 32-bit Windows

Status: RESOLVED WORKSFORME

(Firefox Build System :: General, defect)

Description

[Henri Sivonen (:hsivonen) (away from Bugzilla until 2025-12-29)]

In order to evaluate whether we should de-support non-SSE2 CPUs, it would be useful to have a way to have an option (that's easy to turn on for a tryserver build) to build for 32-bit Windows with SSE2 autovectorization and floating-point math enabled.

Comment 1

[(not currently active) Ted Mielczarek]

I assume there are specific MSVC compiler flags you'd want to use here? If so, sticking them in CFLAGS/CXXFLAGS should be sufficient for testing.

Comment 2

[Ralph Giles (:rillian)]

Will that override the default `-arch:IA32` in old-configure.in? One would need `-arch:SSE2` (the default) at minimum I think. Unless you meant hacking up that setting instead of a mozconfig override.

Comment 3

[Ralph Giles (:rillian)]

I don't have any experience with this, but looking at the docs, I did find there's a diagnostic `/Qpar-report:2` option which logs success/failure messages for autovectorization. Counting those would be an additional metric for the advantage of dropping `/arch:IA32`.

Comment 4

[Mike Hommey [:glandium] OoO until Dec 30]

Replacing -arch:IA32 with -arch:SSE in old-configure.in and js/src/old-configure.in for a try build shouldn't be harder than adding an ac_add_options to the right mozconfigs. Why not do the former?

Comment 5

[Henri Sivonen (:hsivonen) (away from Bugzilla until 2025-12-29)]

(In reply to Ted Mielczarek [:ted.mielczarek] from comment #1)
> I assume there are specific MSVC compiler flags you'd want to use here? If
> so, sticking them in CFLAGS/CXXFLAGS should be sufficient for testing.

I filed the bug, because I didn't know what flags I wanted.

Anyway, it seems that bug 1271794 is making this bug obsolete. Marking as WORKSFORME in anticipation of bug 1271794 landing.