[chromium-dev] Windows component build become 1.3~1.4x faster

[Takuto Ikuta]

Hi chromium developers (especially on windows).

I just landed a CL
<https://chromium-review.googlesource.com/c/1317069> enabling
a new clang flag "/Zc:dllexportInlines-" (draft document
<https://reviews.llvm.org/D54319>) collaborating with chrome c++ toolchain
team (hans <***@chromium.org>, thakis <***@chromium.org> and rnk
<***@chromium.org>).
This flag makes windows component build 1.3~1.4x faster with goma
<https://docs.google.com/document/d/1_W-RsPe5LMz8LOm2Cz1hQ9OlmpTNARbBzARaM81RBYM/edit?usp=sharing>
and
1.1~1.3x faster without goma <https://reviews.llvm.org/D51340>.
I hope this give windows developer better experience of faster edit and
test cycles on windows.

But you may see linker error like

[97/1686] LINK net_unittests.exe

FAILED: net_unittests.exe
ninja -t msvc -e environment.x86 --
../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo
/OUT:./net_unittests.exe /PDB:./net_unittests.exe.pdb
@./net_unittests.exe.rsp
lld-link: error: undefined symbol: "bool __thiscall
net::internal::ClientSocketPoolBaseHelper::Group::RequestWithHandleHasJobForTesting(class
net::ClientSocketHandle const *) const"
@***@internal@net@@***@4@@Z)

referenced by

obj/net/net_unittests/client_socket_pool_base_unittest.obj:("bool
__thiscall
net::internal::ClientSocketPoolBaseHelper::RequestInGroupWithHandleHasJobForTesting(class
std::basic_string<char, struct std::char_traits<char>, class
std::allocator<char>> const &, class net::ClientSocketHandle const *)
@***@net@@QBE_NABV?$***@DU?$***@D@std@
@V?$***@D@2@@std@@***@3@@Z))

If you see this kind of error, please add export attribute to the class
<https://chromium-review.googlesource.com/c/chromium/src/+/1322333> (this
is recommended, but not always work) or function
<https://chromium-review.googlesource.com/c/chromium/src/+/1322331/2/third_party/blink/renderer/core/paint/ng/ng_paint_fragment.h>
where the undefined symbol is defined.

Also if you see other strange behavior, please let me know.

Thanks, Takuto

[Hans Wennborg]

Post by Takuto Ikuta
Hi chromium developers (especially on windows).
I just landed a CL enabling a new clang flag "/Zc:dllexportInlines-" (draft
document) collaborating with chrome c++ toolchain team (hans, thakis and
rnk).
This flag makes windows component build 1.3~1.4x faster with goma and
1.1~1.3x faster without goma.
I hope this give windows developer better experience of faster edit and test
cycles on windows.
But you may see linker error like

Post by Takuto Ikuta
[97/1686] LINK net_unittests.exe
FAILED: net_unittests.exe
ninja -t msvc -e environment.x86 --
../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo
/OUT:./net_unittests.exe /PDB:./net_unittests.exe.pdb
@./net_unittests.exe.rsp
lld-link: error: undefined symbol: "bool __thiscall
net::internal::ClientSocketPoolBaseHelper::Group::RequestWithHandleHasJobForTesting(class
net::ClientSocketHandle const *) const"

referenced by
obj/net/net_unittests/client_socket_pool_base_unittest.obj:("bool __thiscall
net::internal::ClientSocketPoolBaseHelper::RequestInGroupWithHandleHasJobForTesting(class
std::basic_string<char, struct std::char_traits<char>, class
std::allocator<char>> const &, class net::ClientSocketHandle const *) const"

If you see this kind of error, please add export attribute to the class
(this is recommended, but not always work) or function where the undefined
symbol is defined.

The Clang User's Manual
https://clang.llvm.org/docs/UsersManual.html#the-zc-dllexportinlines-option
has some info on how this flag works and why it can create new link
errors.

[b***@chromium.org]

Another (related) benefit of this change is that .obj files get *much* smaller
in component builds. In one test of this change the total size of my .obj
files dropped from 30.7 GB to 18.5 GB. This has obvious implications for
disk cache effectiveness, the ability to have multiple output directories
on a small disk, and on link times (especially on slow disks or after the
files have aged out of the disk cache).

Excellent work.

Post by Takuto Ikuta

Post by Takuto Ikuta
Hi chromium developers (especially on windows).
I just landed a CL enabling a new clang flag "/Zc:dllexportInlines-"

(draft

Post by Takuto Ikuta
document) collaborating with chrome c++ toolchain team (hans, thakis and
rnk).
This flag makes windows component build 1.3~1.4x faster with goma and
1.1~1.3x faster without goma.
I hope this give windows developer better experience of faster edit and

test

Post by Takuto Ikuta
cycles on windows.
But you may see linker error like

Post by Takuto Ikuta
[97/1686] LINK net_unittests.exe
FAILED: net_unittests.exe
ninja -t msvc -e environment.x86 --
../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo
/OUT:./net_unittests.exe /PDB:./net_unittests.exe.pdb
@./net_unittests.exe.rsp
lld-link: error: undefined symbol: "bool __thiscall

net::internal::ClientSocketPoolBaseHelper::Group::RequestWithHandleHasJobForTesting(class

Post by Takuto Ikuta

Post by Takuto Ikuta
net::ClientSocketHandle const *) const"

referenced by
obj/net/net_unittests/client_socket_pool_base_unittest.obj:("bool

__thiscall
net::internal::ClientSocketPoolBaseHelper::RequestInGroupWithHandleHasJobForTesting(class

Post by Takuto Ikuta

Post by Takuto Ikuta

std::basic_string<char, struct std::char_traits<char>, class
std::allocator<char>> const &, class net::ClientSocketHandle const

*) const"

Post by Takuto Ikuta
If you see this kind of error, please add export attribute to the class
(this is recommended, but not always work) or function where the

undefined

Post by Takuto Ikuta
symbol is defined.

The Clang User's Manual
https://clang.llvm.org/docs/UsersManual.html#the-zc-dllexportinlines-option
has some info on how this flag works and why it can create new link
errors.

[Nico Weber]

There's a longer write-up of what this change does at
http://blog.llvm.org/2018/11/30-faster-windows-builds-with-clang-cl_14.html
for people who are curious.

Post by Takuto Ikuta
Hi chromium developers (especially on windows).
I just landed a CL <https://chromium-review.googlesource.com/c/1317069> enabling
a new clang flag "/Zc:dllexportInlines-" (draft document
<https://reviews.llvm.org/D54319>) collaborating with chrome c++
This flag makes windows component build 1.3~1.4x faster with goma
<https://docs.google.com/document/d/1_W-RsPe5LMz8LOm2Cz1hQ9OlmpTNARbBzARaM81RBYM/edit?usp=sharing> and
1.1~1.3x faster without goma <https://reviews.llvm.org/D51340>.
I hope this give windows developer better experience of faster edit and
test cycles on windows.
But you may see linker error like
[97/1686] LINK net_unittests.exe

FAILED: net_unittests.exe
ninja -t msvc -e environment.x86 --
../../third_party/llvm-build/Release+Asserts/bin/lld-link.exe /nologo
/OUT:./net_unittests.exe /PDB:./net_unittests.exe.pdb
@./net_unittests.exe.rsp
lld-link: error: undefined symbol: "bool __thiscall
net::internal::ClientSocketPoolBaseHelper::Group::RequestWithHandleHasJobForTesting(class
net::ClientSocketHandle const *) const"
@***@internal@net@@***@4
@@Z)

referenced by

obj/net/net_unittests/client_socket_pool_base_unittest.obj:("bool
__thiscall
net::internal::ClientSocketPoolBaseHelper::RequestInGroupWithHandleHasJobForTesting(class
std::basic_string<char, struct std::char_traits<char>, class
std::allocator<char>> const &, class net::ClientSocketHandle const *)
@***@net@@QBE_NABV?$***@DU?$***@D@std@
@V?$***@D@2@@std@@***@3@@Z))

If you see this kind of error, please add export attribute to the class
<https://chromium-review.googlesource.com/c/chromium/src/+/1322333> (this
is recommended, but not always work) or function
<https://chromium-review.googlesource.com/c/chromium/src/+/1322331/2/third_party/blink/renderer/core/paint/ng/ng_paint_fragment.h>
where the undefined symbol is defined.
Also if you see other strange behavior, please let me know.
Thanks, Takuto