Unify and simplify the FastCloneShallowArrayStub

Unify and simplify the FastCloneShallowArrayStub

- Don't bake in length/capacity into full codegen calls of stubs,
  allowing boilerplates to increase their capacity without regenerating
  code.
- Unify all variants of the clone stub into a single,
  length-independent version.
- Various tweaks to make sure that the clone stub doesn't spill and
  therefore need an eager stack frame.
- Handle all lengths of array literals in the fast case.

R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=20974

[danno, 2014-04-24 16:55:32]

PTAL

[mvstanton, 2014-04-25 08:25:17]

Neat! With comments addressed, LGTM.

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2580
src/hydrogen.cc:2580: // register pressure in code stubs that otherwise would
spill and create
Nice!

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2633
src/hydrogen.cc:2633: HValue* HGraphBuilder::BuildCloneShallowArrayNoElements(
I don't like the name that much, it surprises me that a function with them name
would leave 1/2 of the JSArray uninitialized.

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2657
src/hydrogen.cc:2657: for (int i = 0; i < JSArray::kElementsOffset; i +=
kPointerSize) {
This is simply a map store, can we eliminate the loop and just store the map?

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2658
src/hydrogen.cc:2658: if (i != JSArray::kElementsOffset) {
As written, this check would always succeed.

[danno, 2014-04-25 11:54:16]

Committed patchset #5 manually as r20974 (presubmit successful).

[danno, 2014-04-25 16:56:42]

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2633
src/hydrogen.cc:2633: HValue* HGraphBuilder::BuildCloneShallowArrayNoElements(
On 2014/04/25 08:25:17, mvstanton wrote:
> I don't like the name that much, it surprises me that a function with them
name
> would leave 1/2 of the JSArray uninitialized. 

Done.

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2657
src/hydrogen.cc:2657: for (int i = 0; i < JSArray::kElementsOffset; i +=
kPointerSize) {
On 2014/04/25 08:25:17, mvstanton wrote:
> This is simply a map store, can we eliminate the loop and just store the map?

Done.

https://codereview.chromium.org/257563004/diff/60001/src/hydrogen.cc#newcode2658
src/hydrogen.cc:2658: if (i != JSArray::kElementsOffset) {
On 2014/04/25 08:25:17, mvstanton wrote:
> As written, this check would always succeed.

Done.