ChangeTaggedSignedToInt32(ChangeCompressedSignedToTaggedSigned((x)) ->
  ChangeCompressedSignedToInt32(x)

This pattern shows up in the Octane Richards benchmark (on arm64):

    sxtw x11, w10
    asr w11, w11, #1

This patch will remove the sxtw.

ChangeCompressedSignedToInt32(CheckedInt32ToCompressedSigned(x)) -> x

This pattern shows up in the Octane Richards benchmark (on arm64):

    adds w10, w10, w10
    b.vs #+0x1118
    asr w11, w10, #1
    stur w10, [x6, #19]
    cmp w11, #0x1a

This patch will remove the asr, and produce:

    adds w11, w10, w10
    b.vs #+0x1108
    stur w11, [x6, #19]
    cmp w10, #0x1a

Bug: v8:7703
Change-Id: I5843e0a4f723b202857ee86130f835cd048d7e31
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1763529Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Rodolph Perfetta <rodolph.perfetta@arm.com>
Cr-Commit-Position: refs/heads/master@{#63389}