FYI: 
1. There was an issue in seabios with this clang version (cr/181247700). So we may have to update seabios if it is used anywhere in ChromeOS e.g. Qemu.

2. cherry pick r321510 (cr/180963915).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/be9b2623eb770d4be5f51eab652b371c833f24a3

commit be9b2623eb770d4be5f51eab652b371c833f24a3
Author: Ting-Yuan Huang <laszio@chromium.org>
Date: Fri Jan 19 08:29:48 2018

autofdo: uprev ebuild to force a rebuild.

There is an ABI change in LLVM and the prebuilt package needs to be
rebuilt.

BUG= chromium:800984 
TEST=cros tryjob chell-chrome-pfq

Change-Id: Id363a4070e7e3121cf874605dc7bdafe43baf67a
Reviewed-on: https://chromium-review.googlesource.com/875234
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Ting-Yuan Huang <laszio@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[add] https://crrev.com/be9b2623eb770d4be5f51eab652b371c833f24a3/sys-devel/autofdo/autofdo-0.18-r2.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/aef1d453cc8dcdf2072be70fe53893121c1fa75d

commit aef1d453cc8dcdf2072be70fe53893121c1fa75d
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Sat Jan 20 04:35:40 2018

toolchain: roll llvm-next to r321490.

BUG= chromium:800984 
TEST=Built packages for chell and daisy.
     Resolved build failures due to new errros:
          http://crbug.com/801269 
	  http://crbug.com/801280 
	  http://crbug.com/801303 

Change-Id: I7850fb86c703198cf966dd1ae664438f83e96720
Reviewed-on: https://chromium-review.googlesource.com/860574
Commit-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>

[add] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-devel/lld/files/lld-invoke-name-llvm-next.patch
[rename] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-devel/clang/clang-6.0_pre317203_p20171212-r1.ebuild
[delete] https://crrev.com/b16daa5195317cab0e77047b756e73ccb74e987f/sys-devel/lld/files/cherry/0c9a338de181a4c5f4905a455ffb424a774d8a3e.patch
[rename] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-devel/lld/lld-6.0_pre317203-r1.ebuild
[rename] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-libs/compiler-rt/compiler-rt-6.0_pre317203-r1.ebuild
[add] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-devel/llvm/files/cherry/1e7ad1c95ade6d20d3e0544772e55e45d2e6edb9.patch
[rename] https://crrev.com/aef1d453cc8dcdf2072be70fe53893121c1fa75d/sys-devel/llvm/llvm-6.0_pre317203_p20171212-r3.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/d1471338d6a893c89ff48e93c4dd4f17f4145fb1

commit d1471338d6a893c89ff48e93c4dd4f17f4145fb1
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Tue Jan 30 00:38:27 2018

sys-devel/{llvm,clang,lld}: backport retpoline patches for llvm-next.

The upstream patches are:
  llvm: https://chromium.googlesource.com/chromiumos/third_party/llvm/+/fd5a8723ce9f2a6b250e85972ef859e4253ea95d
  clang: https://chromium.googlesource.com/chromiumos/third_party/clang/+/0d816739a82da29748caf88570affb9715e18b69
  lld: https://chromium.googlesource.com/external/llvm.org/lld/+/17b90924dbf7eb14c591d72d4e360d77b87fdefc

llvm and clang patches do not apply cleanly on top of our llvm-next (r321490).
I've resolved the conflicts and updated the diffs accordingly.

BUG= chromium:800984 
BUG=chromium:799480
TEST='sudo USE="llvm-next" emerge sys-devel/{llvm,clang,lld}' works.
TEST=Built chell image with llvm-next+retpoline patches. Flashed on a device. Boots fine.
TEST=Built daisy image with llvm-next+retpoline patches. Flashed on a device. Boots fine.
TEST=Built elm image with llvm-next+retpoline patches. Flashed on a device. Boots fine.

Change-Id: Ia2e9d6cceedacbba1b8a3658663827759932fb05
Reviewed-on: https://chromium-review.googlesource.com/890020
Commit-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>

[add] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/lld/files/cherry/17b90924dbf7eb14c591d72d4e360d77b87fdefc.patch
[add] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/llvm/files/cherry/0d816739a82da29748caf88570affb9715e18b69.patch
[rename] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/clang/clang-6.0_pre317203_p20180123-r1.ebuild
[rename] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/llvm/llvm-6.0_pre317203_p20180123-r1.ebuild
[add] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/llvm/files/cherry/fd5a8723ce9f2a6b250e85972ef859e4253ea95d.patch
[rename] https://crrev.com/d1471338d6a893c89ff48e93c4dd4f17f4145fb1/sys-devel/lld/lld-6.0_pre317203-r3.ebuild

llvm will require one more patch with updated retpoline support: https://reviews.llvm.org/D42998.
Git commit 59b64490fda ("[x86/retpoline] Make the external thunk names exactly match the names that happened to end up in GCC.")

CL with the new cherry-pick: https://chromium-review.googlesource.com/907377

and we are still blocked on  Issue 808434 . So, groeck will have to continue building the compiler himself until this is fixed. Hopefully it will be fixed today and we can roll compiler late today.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/cef9bcaa708070db41d41d59a4bb65bcbf93d6b1

commit cef9bcaa708070db41d41d59a4bb65bcbf93d6b1
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Thu Feb 08 09:23:50 2018

sys-devel/llvm: cherry-pick one more retpoline patch for llvm-next.

The upstream patch is:
  https://chromium.googlesource.com/chromiumos/third_party/llvm/+/59b64490fda69d29bb42cfdf7eec37bcc31ff833

BUG= chromium:800984 
BUG=chromium:799480
TEST='sudo USE="llvm-next" emerge sys-devel/llvm' works.

Change-Id: Ie85d06550e09a532f143ff592a0536a6f03d1729
Reviewed-on: https://chromium-review.googlesource.com/907377
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>

[rename] https://crrev.com/cef9bcaa708070db41d41d59a4bb65bcbf93d6b1/sys-devel/llvm/llvm-6.0_pre317203_p20180123-r2.ebuild
[add] https://crrev.com/cef9bcaa708070db41d41d59a4bb65bcbf93d6b1/sys-devel/llvm/files/cherry/59b64490fda69d29bb42cfdf7eec37bcc31ff833.patch

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/810325ed2836e43d3de36e6667128e77dd746699

commit 810325ed2836e43d3de36e6667128e77dd746699
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Thu Feb 15 02:14:03 2018

toolchain: roll llvm, clang, compiler-rt, and lld to version r321490.

This advances llvm, clang, compiler-rt, and lld to the same versions
as llvm-next right now. llvm-next was rolled to this version in
https://chromium-review.googlesource.com/860574

Text matrix: https://docs.google.com/spreadsheets/d/16c7pQS4nttV536FlW5E0GMcQHHbHSrk5KXcUj9f53yo/edit?usp=sharing

BUG= chromium:800984 
TEST=See test matrix.

Change-Id: Ic75a6b330c2a7b2807d5b428df4ced923debcafe
Reviewed-on: https://chromium-review.googlesource.com/896272
Trybot-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>

[delete] https://crrev.com/97346d35d169915ec29b0c71c7418bd9e3dadc3b/sys-devel/lld/files/lld-invoke-name-llvm-next.patch
[delete] https://crrev.com/97346d35d169915ec29b0c71c7418bd9e3dadc3b/sys-devel/llvm/files/cherry/f1cb8efedeb65da55ff87449a6c83ad7e839b090.patch
[rename] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-devel/llvm/llvm-6.0_pre321490_p20180131.ebuild
[modify] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-devel/lld/files/lld-invoke-name.patch
[rename] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-libs/compiler-rt/compiler-rt-6.0_pre321490.ebuild
[rename] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-devel/clang/clang-6.0_pre321490_p20180131.ebuild
[rename] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-devel/lld/lld-6.0_pre321490.ebuild
[rename] https://crrev.com/810325ed2836e43d3de36e6667128e77dd746699/sys-devel/gcc/gcc-4.9.2-r181.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/1b20b7548d6693bfa78f41223b3792a43a7f39b2

commit 1b20b7548d6693bfa78f41223b3792a43a7f39b2
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Fri Feb 23 07:54:22 2018

generic_stages: temporarily ignore all target prebuilts.

Ignore the target prebuilts and rebuild packages from source.

This is a temporary CL. Revert this CL once in has participated in
a green CQ run. This process is documented at:
  https://sites.google.com/a/google.com/chromeos/for-team-members/infrastructure/chromeos-admin/clear_binaries

BUG= chromium:800984 
TEST='./cbuildbot/run_tests' passed.

Change-Id: Ifd6be49037229e1436c257e9f88b1b01222fe80b
Reviewed-on: https://chromium-review.googlesource.com/930221
Commit-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>

[modify] https://crrev.com/1b20b7548d6693bfa78f41223b3792a43a7f39b2/cbuildbot/config_dump.json
[modify] https://crrev.com/1b20b7548d6693bfa78f41223b3792a43a7f39b2/lib/sysroot_lib.py
[modify] https://crrev.com/1b20b7548d6693bfa78f41223b3792a43a7f39b2/cbuildbot/stages/build_stages_unittest.py
[modify] https://crrev.com/1b20b7548d6693bfa78f41223b3792a43a7f39b2/cbuildbot/stages/generic_stages.py
[modify] https://crrev.com/1b20b7548d6693bfa78f41223b3792a43a7f39b2/lib/config_lib.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/3cd58a6a7a651421b1f0f93180455be32e483a68

commit 3cd58a6a7a651421b1f0f93180455be32e483a68
Author: Rahul Chaudhry <rahulchaudhry@chromium.org>
Date: Fri Feb 23 17:06:13 2018

generic_stages: revert 'temporarily ignore all target prebuilts'.

This reverts https://chromium-review.googlesource.com/930221

Stop ignoring the target prebuilts. Chump this CL after CQ master has
had a green build. This process is documented at:
  https://sites.google.com/a/google.com/chromeos/for-team-members/infrastructure/chromeos-admin/clear_binaries

BUG= chromium:800984 
TEST='./cbuildbot/run_tests' passed.

Change-Id: I80826a0b8e9aa209730848ad30ec69469aee53ad
Reviewed-on: https://chromium-review.googlesource.com/930222
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>

[modify] https://crrev.com/3cd58a6a7a651421b1f0f93180455be32e483a68/cbuildbot/config_dump.json
[modify] https://crrev.com/3cd58a6a7a651421b1f0f93180455be32e483a68/lib/sysroot_lib.py
[modify] https://crrev.com/3cd58a6a7a651421b1f0f93180455be32e483a68/cbuildbot/stages/build_stages_unittest.py
[modify] https://crrev.com/3cd58a6a7a651421b1f0f93180455be32e483a68/cbuildbot/stages/generic_stages.py
[modify] https://crrev.com/3cd58a6a7a651421b1f0f93180455be32e483a68/lib/config_lib.py