Port 8798b3ef
Port 1d3c80d3

Original Commit Message:

    - Fixes some incorrect assumptions about padding in the
      code generation. Slots may have apparent extra padding
      when allocation fragments go unused.
    - Reworks 32 bit push code to simplify skipping slot gaps
      when 'push' instructions are used.
    - Adds a ElementSizeInPointers function on machine
      representations.

R=bbudge@chromium.org, joransiu@ca.ibm.com, junyan@redhat.com, midawson@redhat.com
BUG=
LOG=N

Change-Id: I076ae8396434610c52fed040ace5e0f49ea3ef88
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2673142
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Reviewed-by: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/master@{#72516}