Cleanup of class id loading sequences.

Cleanup of class id loading sequences.

These ended up looking performance neutral, but
the cleanup is probably good.

R=srdjan@google.com, vegorov@google.com

Committed: https://code.google.com/p/dart/source/detail?r=38333

[srdjan, 2014-07-16 21:59:01]

Please add tests for cmpb instruction.

LGTM

https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64.cc
File runtime/vm/stub_code_x64.cc (right):

https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64...
runtime/vm/stub_code_x64.cc:1275: // __ cmpq(RAX, Immediate(0));
Remove dead code.

[zra, 2014-07-16 22:53:45]

Tests added.

https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64.cc
File runtime/vm/stub_code_x64.cc (right):

https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64...
runtime/vm/stub_code_x64.cc:1275: // __ cmpq(RAX, Immediate(0));
On 2014/07/16 21:59:01, srdjan wrote:
> Remove dead code.

Done.

[zra, 2014-07-16 23:41:12]

On 2014/07/16 22:53:45, zra wrote:
> Tests added.
> 
>
https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64.cc
> File runtime/vm/stub_code_x64.cc (right):
> 
>
https://codereview.chromium.org/392343002/diff/20001/runtime/vm/stub_code_x64...
> runtime/vm/stub_code_x64.cc:1275: // __ cmpq(RAX, Immediate(0));
> On 2014/07/16 21:59:01, srdjan wrote:
> > Remove dead code.
> 
> Done.

Missed a problem with MIPS. Will include with next change along with some
changes for ARM.

[Vyacheslav Egorov (Google), 2014-07-16 23:57:15]

LGTM

thanks for doing this.

https://codereview.chromium.org/392343002/diff/60001/runtime/vm/assembler_arm...
File runtime/vm/assembler_arm64.cc (right):

https://codereview.chromium.org/392343002/diff/60001/runtime/vm/assembler_arm...
runtime/vm/assembler_arm64.cc:1100: LoadObject(TMP, Object::null_object(), PP);
Loading null requires either memory read from constant pool or movw/movt pair. 

We could apply the same idea here that we use on x86: pool a value into constant
pool that is kSmiCid shifted by class id shift then put into TMP an address of
ConstantPool + IndexOfThatValue - kHeapObjectTag.

[zra, 2014-07-17 15:50:11]

Fixed MIPS and ARM as well.

https://codereview.chromium.org/392343002/diff/60001/runtime/vm/assembler_arm...
File runtime/vm/assembler_arm64.cc (right):

https://codereview.chromium.org/392343002/diff/60001/runtime/vm/assembler_arm...
runtime/vm/assembler_arm64.cc:1100: LoadObject(TMP, Object::null_object(), PP);
On 2014/07/16 23:57:15, Vyacheslav Egorov (Google wrote:
> Loading null requires either memory read from constant pool or movw/movt pair.

> 
> We could apply the same idea here that we use on x86: pool a value into
constant
> pool that is kSmiCid shifted by class id shift then put into TMP an address of
> ConstantPool + IndexOfThatValue - kHeapObjectTag.


That will work in LoadClassIdInstr, but we can't add arbitrary entries to an
object pool in a stub, in general, so it wouldn't work in the check inline cache
stub. (null is fine since null is guaranteed to be in every object pool.)
Loading a 64-bit immediate not from the constant pool on arm64 is up to 4
instructions.

Anyway, I'll try your suggestion in LoadClassIdInstr, but leave this sequence
alone.

[zra, 2014-07-17 16:20:18]

Committed patchset #5 manually as r38333 (presubmit successful).