This is a reland of a72b2f88
Original change's description:
> [arm] Restrict grouping pushes before a TailCall to registers only
>
> We optimize parallel moves performed before a TailCall by grouping adjacent
> pushes. This way, we may use a single instruction to push multiple registers at
> once. However, we also have support for pushing immediates and stack slots for
> which the benefit is questionnable therefore this patch removes support for
> them.
>
> Concerning immediate pushes, it looks like a mistake since we do not have
> support for this case in `AssembleMove` so this patch removes it. Furthermore,
> if we add a test for this case, we see that a `push ip` instruction is
> generated, effectively pushing whatever was in `ip` at the time instead of
> pushing a constant.
>
> Concerning stack slot pushes, we generate a more or less equivalent sequence of
> instructions.
>
> Finally, grouping floating point pushes is not used anywhere so this patch
> removes support for this also.
>
> Bug: v8:6553
> Change-Id: I9b820d33361fc442dd813f66e1f96cda41009110
> Reviewed-on: https://chromium-review.googlesource.com/567191
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
> Cr-Commit-Position: refs/heads/master@{#46718}

Bug: v8:6553
Change-Id: Ib9a55dae7cc5db6185d163c56088ff23426d04bb
Reviewed-on: https://chromium-review.googlesource.com/576087Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Cr-Commit-Position: refs/heads/master@{#46754}