Use register allocator for context on x64.

Use register allocator for context on x64.

BUG=
R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=17585

[Yang, 2013-10-29 14:33:18]

In unoptimized code, we use a fixed register for the context (esi, rsi, cp). In
optimized code for ia32, ARM and MIPS however we use the register allocator for
that. The trick is to make sure that we put the context back to the fixed
register when we leave optimized code (stub calls, runtime calls, unoptimized
functions).

Having the context allocated by the register allocator frees up the fixed
register to be freely allocatable, and allows cross context inlining, as we can
just put the correct context of the inlined function where we need it (not
possible with an untouched fixed register).

Specifically, this requires many LInstructions in x64 to have an operand for the
context. A lot has simply been ported over from ia32.

I also made changes to two LInstructions in ia32 that do not need the context.

[mvstanton, 2013-10-31 08:39:24]

lgtm, small nit.

https://codereview.chromium.org/50863002/diff/1/src/hydrogen.cc
File src/hydrogen.cc (left):

https://codereview.chromium.org/50863002/diff/1/src/hydrogen.cc#oldcode6513
src/hydrogen.cc:6513: #if V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_ARM ||
V8_TARGET_ARCH_MIPS
TODO achieved :)

https://codereview.chromium.org/50863002/diff/1/test/cctest/test-code-stubs-x...
File test/cctest/test-code-stubs-x64.cc (right):

https://codereview.chromium.org/50863002/diff/1/test/cctest/test-code-stubs-x...
test/cctest/test-code-stubs-x64.cc:68: int double_argument_slot =
nit: Could you illuminate this block with a comment?

[Yang, 2013-11-08 10:59:04]

Committed patchset #2 manually as r17585 (presubmit successful).