1415229 - (WinLTO) Support lld-link and ThinLTO in clang-cl builds

Status: RESOLVED FIXED

(Firefox Build System :: General, enhancement)

Description

[(Away)]

I was able to get cross-TU inlining using ThinLTO on a toy program. Let's see if we can scale this up to full Firefox builds.

$ cat foo.cpp
int seven();
int main() { return seven(); }

$ cat bar.cpp
int seven() { return 7; }

$ rm -f *.obj *.pdb *.exe
$ clang-cl -O2 -c *.cpp
$ lld-link -out:a.exe -debug *.obj
$ cdb -z a.exe -c 'uf a!main; q'
a!main:
00000001`4000f010 e9ebffffff      jmp     a!seven (00000001`4000f000)

$ rm -f *.obj *.pdb *.exe
$ clang-cl -flto=thin -O2 -c *.cpp
$ lld-link -out:a.exe -debug *.obj
$ cdb -z a.exe -c 'uf a!main; q'
a!main:
00000001`4000f010 b807000000      mov     eax,7
00000001`4000f015 c3              ret


(Tested with LLVM trunk, rev 317336)

Comment 1

[(Away)]

Dependencies are resolved and ThinLTO nightlies have been shipping for a few weeks now.