The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/398b188eab96c3b198b6a4eb8788bba77202aef8

commit 398b188eab96c3b198b6a4eb8788bba77202aef8
Author: Samuel Huang <huangs@chromium.org>
Date: Fri Jan 11 20:00:13 2019

[Zucchini] ARM Support: Add arm_utils.* with tests.

This CL adds new files for ARM support. The code is not yet integrated
into Zucchini, but are only used by the added tests. The high-level
goal is to support rel32 reference read / write via:

    (data bytes) <-> |code| <-> |disp| <-> |target_rva|,

where |code| is ARM machine code value (read-write), and |disp| is a
PC-relative displacement. Details:
* Add template class ArmAddrTraits as API to process rel32 references.
  It is specialized for each rel32 address type, and aggregates
  selected low-level static functions from an ARM *Translator class.
* Add class Arm32Rel32Translator for 32-bit ARM (ARM32)
  * ArmAddrTraits is specialized to {A24} encoding for ARM mode, and
    {T8, T11, T21, T24} encodings for THUMB2 mode.
  * Complication: |code| can affect |disp| <-> |target_rva|, since the
    the BLX instruction dictates whether |target_rva| should be 2-byte
    or 4-byte aligned!
* The BLX special case makes |disp| <-> |target_rva| unsuitable for
  ArmAddrTraits. This led to the API to be defined as:
  * Fetch() for (data bytes) -> |code|.
  * Store() for |code| -> (data bytes).
  * Decode() for |code| -> |disp| & alignment spec (ArmAlign).
  * Encode() for |disp| -> |code|: Modifies existing |code|.
  * Read() for |code| -> |target_rva|: Needs |instr_rva|.
  * Write() for |target_rva| -> |code|.
    * Needs |instr_rva|; modifies existing |code|.
* Add class AArch64Rel32Translator for 64-bit ARM (AArch64).
  * ArmAddrTraits is specialized to {Immd14, Immd19, Immd26} encodings.

Bug: 918867
Change-Id: Ie20935e391ed0ac85c408aa9c8959305dc8bba42
Reviewed-on: https://chromium-review.googlesource.com/c/1394397
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622115}
[modify] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/BUILD.gn
[add] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/arm_utils.cc
[add] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/arm_utils.h
[add] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/arm_utils_unittest.cc
[modify] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/reference_bytes_mixer.cc
[modify] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/reference_bytes_mixer.h
[modify] https://crrev.com/398b188eab96c3b198b6a4eb8788bba77202aef8/components/zucchini/zucchini_gen.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/64b76696cded1502e1f9dd055dd3e2a51fa70f80

commit 64b76696cded1502e1f9dd055dd3e2a51fa70f80
Author: Samuel Huang <huangs@chromium.org>
Date: Wed Jan 16 15:31:06 2019

[Zucchini] ARM code: Fix counting mistake; rename T21 to T20.

ARM instruction B encoding T3 specifies:
  |code|: 11110Scc cciiiiii 10(J1)0(J2)jjj jjjjjjjj
  |disp|: SSSSSSSS SSSS(J2)(J1)ii iiiijjjj jjjjjjj0

There are 20 bits in |code| dedicated for |disp|:
  S iiiiii (J1)(J2)jjj jjjjjjjj

Previously this was miscounted as 21! This CL corrects the mistake, and
renames "T21" to "T20". There's no change in behavior.

Bug: 918867
Change-Id: Ie571bc1a413c4b77f2017cfd2ffe8bf99975ef7a
Reviewed-on: https://chromium-review.googlesource.com/c/1413352
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623243}
[modify] https://crrev.com/64b76696cded1502e1f9dd055dd3e2a51fa70f80/components/zucchini/arm_utils.cc
[modify] https://crrev.com/64b76696cded1502e1f9dd055dd3e2a51fa70f80/components/zucchini/arm_utils.h
[modify] https://crrev.com/64b76696cded1502e1f9dd055dd3e2a51fa70f80/components/zucchini/arm_utils_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/88de28e56330d97fe046755fee972495d5e5749d

commit 88de28e56330d97fe046755fee972495d5e5749d
Author: Samuel Huang <huangs@chromium.org>
Date: Fri Jan 18 19:36:50 2019

[Zucchini] ARM code: Add alignment checks for Read*() / Write*(); add tests.

Read*() / Write*() functions for ARM code take |instr_rva|, and
translate |code| <-> |target_rva|. Both |instr_rva| and |target_rva|
must be properly aligned (2-bytes or 4-bytes), but previously such
checks were only done on |target_rva - PC(instr_rva)|. This CL adds:
* Alignment checks for input params of Read*() / Write*().
* Unit tests for Read*() / Write*().

Also update high-level comments in arm_utils.h.

Bug: 918867
Change-Id: Ie37d2df621411920b54ef699edaed1d90eacba88
Reviewed-on: https://chromium-review.googlesource.com/c/1415753
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624236}
[modify] https://crrev.com/88de28e56330d97fe046755fee972495d5e5749d/components/zucchini/arm_utils.cc
[modify] https://crrev.com/88de28e56330d97fe046755fee972495d5e5749d/components/zucchini/arm_utils.h
[modify] https://crrev.com/88de28e56330d97fe046755fee972495d5e5749d/components/zucchini/arm_utils_unittest.cc