Use a loop in generated code to allocate stack slots for function with many l...

Use a loop in generated code to allocate stack slots for function with many local variables.

If a function contains more than a certain number of locals (IA32: 9, X64: 6, ARM: 4) 
a loop for initializing the locals with 'undefined' is more compact. 
For less locals we unroll that loop by emitting a sequence of push instructions.


Committed: http://code.google.com/p/v8/source/detail?r=3521

[Mads Ager (chromium), 2009-12-23 14:30:52]

LGTM with a couple of nits.

http://codereview.chromium.org/515012/diff/1/4
File src/arm/virtual-frame-arm.cc (right):

http://codereview.chromium.org/515012/diff/1/4#newcode149
src/arm/virtual-frame-arm.cc:149: if (count < 5) {
Please introduce a platform-dependent named constant for this value.

http://codereview.chromium.org/515012/diff/1/4#newcode155
src/arm/virtual-frame-arm.cc:155: // For more kocals a loop in generated code is
more compact.
kocals -> locals

http://codereview.chromium.org/515012/diff/1/2
File src/ia32/virtual-frame-ia32.cc (right):

http://codereview.chromium.org/515012/diff/1/2#newcode543
src/ia32/virtual-frame-ia32.cc:543: for (int i = 0; i < count; i++) {
This loop should be extracted.  It happens in all branches, so you can just
always do it at the end.

http://codereview.chromium.org/515012/diff/1/3
File src/x64/virtual-frame-x64.cc (right):

http://codereview.chromium.org/515012/diff/1/3#newcode155
src/x64/virtual-frame-x64.cc:155: for (int i = 0; i < count; i++) {
Ditto.

[fschneider, 2009-12-23 15:16:38]

http://codereview.chromium.org/515012/diff/1/4
File src/arm/virtual-frame-arm.cc (right):

http://codereview.chromium.org/515012/diff/1/4#newcode149
src/arm/virtual-frame-arm.cc:149: if (count < 5) {
On 2009/12/23 14:30:52, Mads Ager wrote:
> Please introduce a platform-dependent named constant for this value.

Done.

http://codereview.chromium.org/515012/diff/1/4#newcode155
src/arm/virtual-frame-arm.cc:155: // For more kocals a loop in generated code is
more compact.
On 2009/12/23 14:30:52, Mads Ager wrote:
> kocals -> locals

Done.

http://codereview.chromium.org/515012/diff/1/2
File src/ia32/virtual-frame-ia32.cc (right):

http://codereview.chromium.org/515012/diff/1/2#newcode543
src/ia32/virtual-frame-ia32.cc:543: for (int i = 0; i < count; i++) {
On 2009/12/23 14:30:52, Mads Ager wrote:
> This loop should be extracted.  It happens in all branches, so you can just
> always do it at the end.

Done.

http://codereview.chromium.org/515012/diff/1/3
File src/x64/virtual-frame-x64.cc (right):

http://codereview.chromium.org/515012/diff/1/3#newcode155
src/x64/virtual-frame-x64.cc:155: for (int i = 0; i < count; i++) {
On 2009/12/23 14:30:52, Mads Ager wrote:
> Ditto.

Done.