The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c9ee8b32a9740805d519c57cef154c9d30b7db98

commit c9ee8b32a9740805d519c57cef154c9d30b7db98
Author: Peter Collingbourne <pcc@chromium.org>
Date: Thu Feb 08 02:28:38 2018

build: Increase linker optimization level to -O2.

This enables string tail merge optimization in gold and lld.
It decreased the size of an official build of libmonochrome.so
by 150KB.

Bug: 810154
Change-Id: I69a6446a2dfccbe0b438477661087524bf1018e9
Reviewed-on: https://chromium-review.googlesource.com/907635
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Peter Collingbourne <pcc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535268}
[modify] https://crrev.com/c9ee8b32a9740805d519c57cef154c9d30b7db98/build/config/compiler/BUILD.gn

I've attached a prototype patch that implements string tail merging in COFF lld. Here's the effect on binary size in an official build:

Without tail merging:
02/28/2018  07:32 PM        75,499,008 chrome_child0.dll
03/02/2018  03:40 PM        52,397,568 chrome0.dll

With tail merging:
02/28/2018  07:33 PM        75,318,784 chrome_child1.dll
03/02/2018  03:41 PM        52,308,480 chrome1.dll

So that's about 270KB saved overall.

Deleted: 0001-string-tail-merging.patch 7.0 KB

0001-string-tail-merging.patch 7.0 KB Download

Could you send this patch for review?

It's still a little prototypish, so I haven't sent it for review yet. I'll try to do that soon.

Sent https://reviews.llvm.org/D44504

r327668

The roll landed, so this is now blocked on switching to lld on Windows.

Removing Android label since this is now done on Android

It's also done on Linux.

As https://chromium-review.googlesource.com/c/chromium/src/+/907635 there is nothing to do on Windows but is macOS/iOS OK? If so this can be closed I guess.

We had to disable string tail merging on Windows because it regressed compressed binary size (see https://bugs.chromium.org/p/chromium/issues/detail?id=838449#c24). I'd still like to re-enable it on Windows by figuring out a way to avoid the regression.