Refactor bigint shifting code in preparation of shifting intrinsics.

Refactor bigint shifting code in preparation of shifting intrinsics.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44764

[regis, 2015-03-27 21:43:43]

regis@google.com changed reviewers:
+ srdjan@google.com

[srdjan, 2015-03-27 22:29:55]

lgtm

https://codereview.chromium.org/1044503002/diff/1/runtime/lib/bigint.dart
File runtime/lib/bigint.dart (right):

https://codereview.chromium.org/1044503002/diff/1/runtime/lib/bigint.dart#new...
runtime/lib/bigint.dart:263: final bs = n % _DIGIT_BITS;
You compute now ds and bs twice: once here and once in caller. I guess it has no
performance impact because DIGIT_BITS is power of 2 and the oberhead of loop
dominates

https://codereview.chromium.org/1044503002/diff/1/runtime/vm/method_recognizer.h
File runtime/vm/method_recognizer.h (right):

https://codereview.chromium.org/1044503002/diff/1/runtime/vm/method_recognize...
runtime/vm/method_recognizer.h:405: V(_Bigint, _rsh, Bigint_rsh, 1239668932)    
                                \
You may want to add this only after you have implemented intrinsics?

[regis, 2015-03-27 22:41:47]

Thanks!

https://codereview.chromium.org/1044503002/diff/1/runtime/lib/bigint.dart
File runtime/lib/bigint.dart (right):

https://codereview.chromium.org/1044503002/diff/1/runtime/lib/bigint.dart#new...
runtime/lib/bigint.dart:263: final bs = n % _DIGIT_BITS;
On 2015/03/27 22:29:54, srdjan wrote:
> You compute now ds and bs twice: once here and once in caller. I guess it has
no
> performance impact because DIGIT_BITS is power of 2 and the oberhead of loop
> dominates

Correct. It is cheaper to recalculate the values from n, rather than pass them
as additional arguments.

https://codereview.chromium.org/1044503002/diff/1/runtime/vm/method_recognizer.h
File runtime/vm/method_recognizer.h (right):

https://codereview.chromium.org/1044503002/diff/1/runtime/vm/method_recognize...
runtime/vm/method_recognizer.h:405: V(_Bigint, _rsh, Bigint_rsh, 1239668932)    
                                \
On 2015/03/27 22:29:54, srdjan wrote:
> You may want to add this only after you have implemented intrinsics?

OK, I will wait until the first intrinsic is implemented.

[regis, 2015-03-27 22:42:00]

Committed patchset #2 (id:20001) manually as r44764 (presubmit successful).