ARM: Fix double use of IP when storing object fields with large offsets.

ARM: Fix double use of IP when storing object fields with large offsets.

TEST=language/large_class_declaration --noopt
R=fschneider@google.com

Committed: https://github.com/dart-lang/sdk/commit/7e2e9cb949c2f096cfb7c94987f77cb4cf027d3b

[rmacnak, 2015-11-04 20:25:40]

rmacnak@google.com changed reviewers:
+ fschneider@google.com

[Florian Schneider, 2015-11-04 20:58:01]

https://codereview.chromium.org/1409733009/diff/1/runtime/vm/assembler_arm.cc
File runtime/vm/assembler_arm.cc (right):

https://codereview.chromium.org/1409733009/diff/1/runtime/vm/assembler_arm.cc...
runtime/vm/assembler_arm.cc:1884: AddImmediate(IP, object, offset -
kHeapObjectTag);
Same issue here?

https://codereview.chromium.org/1409733009/diff/1/runtime/vm/assembler_arm.cc...
runtime/vm/assembler_arm.cc:1897: LoadObject(IP, value);
Would it work to select in DEBUG mode a temp register != object && != IP here in
the same way as we do inside VerifiedWrite?

https://codereview.chromium.org/1409733009/diff/1/runtime/vm/assembler_arm.cc...
runtime/vm/assembler_arm.cc:1911: ASSERT(object != R9);
Not sure if this is always guaranteed: I think you need to add code to support
object == R9.

[rmacnak, 2015-11-05 01:17:00]

PTAL: Make VerifiedWrite also preserve the object register if it is different
from the field address's base register.

[Florian Schneider, 2015-11-05 01:50:35]

lgtm

https://codereview.chromium.org/1409733009/diff/20001/runtime/vm/assembler_ar...
File runtime/vm/assembler_arm.cc (right):

https://codereview.chromium.org/1409733009/diff/20001/runtime/vm/assembler_ar...
runtime/vm/assembler_arm.cc:1756: if ((object != base) && (object !=
kNoRegister)) {
I guess not checking (object != base) would be ok, too. Like below, we don't
check (adress.rm() != base). I'm ok either way.

[rmacnak, 2015-11-05 17:54:54]

Committed patchset #2 (id:20001) manually as
7e2e9cb949c2f096cfb7c94987f77cb4cf027d3b (presubmit successful).