Refine allocation policy for input operands at calls.

Refine allocation policy for input operands at calls.

For instructions that are marked as calls we can use:

1. Fixed input registers

2. Use-at-start policy (register, memory or constant).

(Memory or constant would not need the use-at-start policy, but
not specifying use-at-start prevents the allocator from using
a register even if there is one available. That's why use-at-start
is required and guarded by assertion)
Committed: http://code.google.com/p/v8/source/detail?r=7616

[Vyacheslav Egorov (Chromium), 2011-04-14 10:49:00]

LGTM