ARM: Support DoCheckInstanceType in lithium codegenerator.

ARM: Support DoCheckInstanceType in lithium codegenerator.

BUG=
TEST=

[Søren Thygesen Gjesse, 2011-01-05 20:52:36]

LGTM if not using ip

Regarding using is as a scratch register we could consider something like the
CpuFeatures::Scope, e.g.

{
  DontScratchIPScope scope;
  <code which relies on ip not changing>
}

and then have an assertion failure is the code causes ip to be used by the
assembler or macro assembler.

But maybe it is not worth it.

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2118: Register scratch = scratch0();
It is convenient to use ip as an intermediate register, but it can be unsafe, as
it is used extensively internally in both the assembler and macro assembler. It
is probably OK with the instructions used here, but is somebody where to later
change it things might break.

I think we should play it save and allocate a temporary for this instruction,
but I think it is not needed after all.

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2123: __ ldr(scratch, FieldMemOperand(input,
HeapObject::kMapOffset));
Can't you just replace type with scratch here?

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2133: if (last != LAST_TYPE) {
No need to reload type - can stay in scratch.

[Karl Klose, 2011-01-06 12:47:14]

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc
File src/arm/lithium-codegen-arm.cc (right):

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2118: Register scratch = scratch0();
I remove the second temporary and use only scratch0.

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2123: __ ldr(scratch, FieldMemOperand(input,
HeapObject::kMapOffset));
On 2011/01/05 20:52:36, Søren Gjesse wrote:
> Can't you just replace type with scratch here?

Done.

http://codereview.chromium.org/6040008/diff/1/src/arm/lithium-codegen-arm.cc#...
src/arm/lithium-codegen-arm.cc:2133: if (last != LAST_TYPE) {
On 2011/01/05 20:52:36, Søren Gjesse wrote:
> No need to reload type - can stay in scratch.

Done.