1448980 - Add an --enable-thinlto (or similar) for Windows

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[(Away)]

When set, this flag should:

* Complain if the linker is not lld-link
* Add -flto=thin to MOZ_OPTIMIZE_FLAGS (probably want to coordinate with bug 1448978)
* Add -FORCE to LDFLAGS until bug 1448976 is addressed
* Change AR and to llvm-lib, and add -llvmlibthin to AR_FLAGS
* Maybe? change HOST_AR to llvm-lib. It seems like we shouldn't need this but I needed it to make my build work. I didn't need to change HOST_AR_FLAGS.

Comment 1

[(Away)]

And possibly also add -OPT:LLDLTO=3 to LDFLAGS.

Comment 2

[(Away)]

(In reply to David Major [:dmajor] from comment #1)
> And possibly also add -OPT:LLDLTO=3 to LDFLAGS.

But be careful with Spidermonkey builds: 
LINK : fatal error LNK1117: syntax error in option 'OPT:LLDLTO=3'

Comment 3

[Mike Hommey [:glandium]]

Something like --enable-lto=thin would probably be better.

Comment 4

[(Away)]

No objection from me.

Comment 5

[(not currently active) Ted Mielczarek]

tjr is working on getting LTO or ThinLTO working with clang builds on Linux as a prerequisite to making clang CFI work, so it'd be great if we could make this work there as well.

Comment 6

[(Away)]

Attachment: Part 0: Rename flags to cflags

I wrote this just to help me understand the next patch better

Comment 7

[(Away)]

Attachment: Make --enable-lto work with clang-cl

Comment 8

[Nathan Froyd [:froydnj]]

Comment on attachment 8992013 [details] [diff] [review]
Make --enable-lto work with clang-cl

Review of attachment 8992013 [details] [diff] [review]:
-----------------------------------------------------------------

Not a huge fan of the massive amount of indentation here, but oh well.  r=me with the change below.

::: build/moz.configure/toolchain.configure
@@ +1332,3 @@
>  
> +    if value:
> +        enabled = "1"

Can we not just make this `True`, and add_old_configure_assignment will DTRT?  Assigning "1" is...weird.

Comment 9

[(Away)]

> Can we not just make this `True`, and add_old_configure_assignment will
> DTRT?  Assigning "1" is...weird.

Sounds good to me. I didn't know add_old_configure_assignment could do that. I was just refactoring the existing "1" code.

Comment 10

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/34a44432715b
prequel: Rename LTO `flags` to `cflags`. r=froydnj
https://hg.mozilla.org/integration/mozilla-inbound/rev/a2ae515ee43f
Make --enable-lto work with clang-cl. r=froydnj

Comment 11

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/34a44432715b
https://hg.mozilla.org/mozilla-central/rev/a2ae515ee43f