the plan is to do the roll on Sunday evening (Aug 6, 2017). The prebuilts will be uploaed by chromiumos-sdk on Monday morning after a delay of 16 hours.

Hopefully, there will be no issue post update.
CCing : akeshet + next week's Infra rotation folks so that they are aware of the planned llvm update.

CL for llvm update: https://chromium-review.googlesource.com/c/602683

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4

commit bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4
Author: Manoj Gupta <manojgupta@google.com>
Date: Sun Aug 06 22:37:58 2017

LLVM: Release version r305632.

This CL updates LLVM in ChromeOS to r305632.
In addition, compiler-rt is enabled as the default compiler
runtime library for llvm.

Links to trybot jobs:
https://docs.google.com/a/google.com/spreadsheets/d/1xVLkraenV8I2EV-UzHArghnBoDUYMX5LiwfxMZ8qmZk/edit?usp=sharing

Autofdo ebuild is updated to ensure that it works both with the current
llvm in paladin builders and the new llvm release.

BUG= chromium:752642 
TEST=https://docs.google.com/a/google.com/spreadsheets/d/1xVLkraenV8I2EV-UzHArghnBoDUYMX5LiwfxMZ8qmZk/edit?usp=sharing
TEST=sudo emerge llvm clang works.
TEST=sudo emerge autofdo works with current/old llvm.

Change-Id: I9d6f5dcfe7a81760fc3a2450666fb36b96374257
Reviewed-on: https://chromium-review.googlesource.com/602683
Reviewed-by: Luis Lozano <llozano@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Manoj Gupta <manojgupta@chromium.org>

[rename] https://crrev.com/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4/sys-devel/llvm/llvm-5.0_pre305632_p20170806.ebuild
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/bde56a96995a329cf1df5716b1f84b32aac6c174.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/llvm-4.0-leak-whitelist.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/revert-71dbb7838bd4a1b84c40da45d4b85353590875b7.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/385d9f6d5abb6b2d4ea27e59ac1e7b0e20d54f7c.patch
[rename] https://crrev.com/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4/sys-devel/clang/clang-5.0_pre305632_p20170806.ebuild
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/96eed06b6e57a3c8e2593e73d6f33bdd407f43b9.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/21b4d8e9b9afa5787894aecde704cd3ef62b10c2.patch
[modify] https://crrev.com/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4/sys-devel/autofdo/autofdo-0.15.ebuild
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/46a48e5918ab64e40ed8b929fdb8d2ff4117cfa1.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/99e2e66daf8d334858cec4f6e8e7a39d6a535a55.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/385d9f6d5abb6b2d4ea27e59ac1e7b0e20d54f7c.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/46a48e5918ab64e40ed8b929fdb8d2ff4117cfa1.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/abf586838958632768fa4c91d7d8be1689e37bf8.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/96eed06b6e57a3c8e2593e73d6f33bdd407f43b9.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/c74078b0a058c70de3504cb2533352ee48e71836.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/llvm-4.0-leak-whitelist.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-libs/compiler-rt/files/cherry/e60a00c0dfb05bad4912315912b70fa35050a058.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/432ed0e4a6d58f7dda8992a167aad43bc91f76c6.patch
[delete] https://crrev.com/94e253e969c1688801b3a867b68774489c715be2/sys-devel/llvm/files/cherry/7217e99fda533e3a439020fa5dfbc23b7b360988.patch
[rename] https://crrev.com/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4/sys-devel/autofdo/autofdo-0.15-r6.ebuild
[rename] https://crrev.com/bbdb4028be8d20f2440ee6530dc0deff1cb1b8b4/sys-libs/compiler-rt/compiler-rt-5.0_pre305632.ebuild

Roll to r305632 is completed. CQ also had a green run.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7

commit 0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7
Author: Manoj Gupta <manojgupta@chromium.org>
Date: Thu Aug 10 22:39:48 2017

generic_stages: temporarily ignore all target prebuilts.

Clear all binaries to build from scratch after llvm roll.

Revert this CL once it 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:752642 
TEST='./cbuildbot/run_tests' passed.

Change-Id: I8ed265609f92afcce1a6ba93cf3548645aabbec4
Reviewed-on: https://chromium-review.googlesource.com/609923
Commit-Ready: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>

[modify] https://crrev.com/0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7/cbuildbot/config_dump.json
[modify] https://crrev.com/0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7/cbuildbot/stages/build_stages_unittest.py
[modify] https://crrev.com/0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7/cbuildbot/stages/generic_stages.py
[modify] https://crrev.com/0ec26a7a84a6ce157c75f5f01b267b78f6f9b5c7/lib/config_lib.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/98661c7ec667982eb7233e8bc56532e43c0a5116

commit 98661c7ec667982eb7233e8bc56532e43c0a5116
Author: Manoj Gupta <manojgupta@google.com>
Date: Thu Aug 10 22:46:42 2017

Revert "generic_stages: temporarily ignore all target prebuilts."

Revert CL: generic_stages: temporarily ignore all target prebuilts.

Clear all binaries to build from scratch after llvm roll.
This process is documented at
https://sites.google.com/a/google.com/chromeos/for-team-members/infrastructure/chromeos-admin/clear_binaries

BUG= chromium:752642 
TEST='./cbuildbot/run_tests' passed.

Change-Id: I611d680215372a99dd3ecf402a213867b5f71465
Reviewed-on: https://chromium-review.googlesource.com/609924
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Trybot-Ready: Manoj Gupta <manojgupta@chromium.org>

[modify] https://crrev.com/98661c7ec667982eb7233e8bc56532e43c0a5116/cbuildbot/config_dump.json
[modify] https://crrev.com/98661c7ec667982eb7233e8bc56532e43c0a5116/cbuildbot/stages/build_stages_unittest.py
[modify] https://crrev.com/98661c7ec667982eb7233e8bc56532e43c0a5116/cbuildbot/stages/generic_stages.py
[modify] https://crrev.com/98661c7ec667982eb7233e8bc56532e43c0a5116/lib/config_lib.py