Do not use deprecated ARM instructions in DirectCEntryStub::GenerateCall.

Do not use deprecated ARM instructions in DirectCEntryStub::GenerateCall.

Non-ancient versions of the ARM-ARM explicitly deprecate most uses of the PC
within instructions and older ARM implementations have a non-predictable offset
(8 or 12) for some of these deprecated uses. Avoiding the deprecated instruction
costs us one additional instruction in DirectCEntryStub::GenerateCall, but this
should not cause any significant performance degradation.

The deoptimizer still uses the PC in a stm instruction, but it is a bit unclear
what to do about that, so simply a comment has been added to reconsider this in
the future.
Committed: http://code.google.com/p/v8/source/detail?r=8916

[danno, 2011-08-12 08:43:10]

LGTM with an added TODO

http://codereview.chromium.org/7633014/diff/1/src/arm/deoptimizer-arm.cc
File src/arm/deoptimizer-arm.cc (right):

http://codereview.chromium.org/7633014/diff/1/src/arm/deoptimizer-arm.cc#newc...
src/arm/deoptimizer-arm.cc:597: // a bit differently.
Maybe add a TODO?

[Sven Panne, 2011-08-12 08:44:47]

On 2011/08/12 08:43:10, danno wrote:
> LGTM with an added TODO
> 
> http://codereview.chromium.org/7633014/diff/1/src/arm/deoptimizer-arm.cc
> File src/arm/deoptimizer-arm.cc (right):
> 
>
http://codereview.chromium.org/7633014/diff/1/src/arm/deoptimizer-arm.cc#newc...
> src/arm/deoptimizer-arm.cc:597: // a bit differently.
> Maybe add a TODO?

Done.

[m.m.capewell, 2011-08-12 11:50:51]

http://codereview.chromium.org/7633014/diff/5001/src/arm/code-stubs-arm.cc
File src/arm/code-stubs-arm.cc (right):

http://codereview.chromium.org/7633014/diff/5001/src/arm/code-stubs-arm.cc#ne...
src/arm/code-stubs-arm.cc:6323: __ add(ip, pc, Operand(4));
Replace 4 with kInstrSize, and assert on the size of the code generated for
str() and Jump().

http://codereview.chromium.org/7633014/diff/5001/src/arm/code-stubs-arm.cc#ne...
src/arm/code-stubs-arm.cc:6335: __ add(ip, pc, Operand(4));
As above.

http://codereview.chromium.org/7633014/diff/5001/src/arm/deoptimizer-arm.cc
File src/arm/deoptimizer-arm.cc (right):

http://codereview.chromium.org/7633014/diff/5001/src/arm/deoptimizer-arm.cc#n...
src/arm/deoptimizer-arm.cc:597: // handle this a bit differently.
The ARM ARM also deprecates using sp in an stm. Additionally, it says
"Instructions with the base register in the list and ! specified [...] the use
of such instructions is deprecated. If the base register is not the
lowest-numbered register in the list, such an instruction stores an UNKNOWN
value for the base register."
Thus, if restored_regs is populated, the updated sp is UNKNOWN. In practice,
this seems to work, but it may break in new ARM implementations.
Perhaps add some debug code to check the sp stored on the stack is as expected?

[Sven Panne, 2011-08-12 14:35:25]

I have made the stub a bit clearer, including an assertion, see
http://codereview.chromium.org/7640016/.

The deoptimizer is still unchanged, I hope that Søren can have a look at it. The
details of the deoptimizer are still a mircale to me... :-}