1448978 - Split out Windows MOZ_OPTIMIZE_FLAGS based on compiler

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[(Away)]

In my local clang-cl builds I just stomp over MOZ_OPTIMIZE_FLAGS. It would be cleaner if old-configure.in would say something like:

if <clang-cl>
  MOZ_OPTIMIZE_FLAGS="-O2"
else
  MOZ_OPTIMIZE_FLAGS="-O1 -Oi"
endif

Comment 1

[Nathan Froyd [:froydnj]]

Do we really want -O2 for clang-cl?  Why not -Os or -Oz, for consistency with what clang/gcc do?

Comment 2

[(Away)]

Unless someone can show me better numbers, -O2 seems to be our only hope of even coming close to MSVC speed: bug 1443590 comment 8

Comment 3

[Nathan Froyd [:froydnj]]

Attachment: use more aggressive optimization flags for clang-cl

We want to use clang-cl to ship Firefox, and the only way we can come
close to MSVC numbers is to use -O2 here, for better or worse.

dmajor, I see in bug 1443590 comment 8 that "binary sizes are much larger than
MSVC's"; is that with using -O2 or some other settings?  We'll probably need to
push harder on that before we get to something shippable...

Comment 4

[(Away)]

Comment on attachment 8962483 [details] [diff] [review]
use more aggressive optimization flags for clang-cl

Yes, this increases code size in order to get us better speed. And ThinLTO makes it a lot worse still. And yes, it will be a major factor to consider before shipping this.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/3619a41def16
use more aggressive optimization flags for clang-cl; r=chmanchester

Comment 6

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/3619a41def16

Comment 7

[(not currently active) Ted Mielczarek]

FWIW I have a patch sitting here to move MOZ_OPTIMIZE_FLAGS into moz.configure, but I got hung up on the fact that js/src uses different defaults.