[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

Until this change, implementation of Dart_IntegerToHexCString()
always created Bigint objects and used Bigint::ToHexCString() to do
the work.

In --limit-ints-to-64-bits mode (with Dart integers limited to 64
bits) Bigints are banned and should not be used.
This CL revises Dart_IntegerToHexCString implementation to avoid
creating Bigint objects for Smi and Mint arguments, so it would
work in --limit-ints-to-64-bits mode.

Also, this CL adds test case to lock down the behavior of
Dart_IntegerToHexCString.

R=asiva@google.com

Issue: https://github.com/dart-lang/sdk/issues/30103
Committed: https://github.com/dart-lang/sdk/commit/3d4838fc70a5439437a5ceb4247551315c294477

[alexmarkov, 2017-07-31 21:00:37]

alexmarkov@google.com changed reviewers:
+ asiva@google.com, zra@google.com

[siva, 2017-07-31 22:03:51]

lgtm

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h
File runtime/vm/object.h (right):

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h#newcode...
runtime/vm/object.h:6465: virtual const char* ToHexCString(Zone* zone) const;
Club this with virtual methods listed above.

Also please add a Note that when the Bigint class this decoupled from Integer
this method can become a regular method (de-virtualized).

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h#newcode...
runtime/vm/object.h:6649: virtual const char* ToHexCString(Zone* zone) const;
Club this with all virtual methods declared above.

[alexmarkov, 2017-08-01 15:42:29]

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h
File runtime/vm/object.h (right):

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h#newcode...
runtime/vm/object.h:6465: virtual const char* ToHexCString(Zone* zone) const;
On 2017/07/31 22:03:51, siva wrote:
> Club this with virtual methods listed above.
> 
> Also please add a Note that when the Bigint class this decoupled from Integer
> this method can become a regular method (de-virtualized).

Done.

https://codereview.chromium.org/2987183002/diff/1/runtime/vm/object.h#newcode...
runtime/vm/object.h:6649: virtual const char* ToHexCString(Zone* zone) const;
On 2017/07/31 22:03:51, siva wrote:
> Club this with all virtual methods declared above.

Done.

[alexmarkov, 2017-08-01 16:00:43]

Description was changed from

==========
[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

Until this change, implementation of Dart_IntegerToHexCString()
always created Bigint objects and used Bigint::ToHexCString() to do
the work.

In --limit-ints-to-64-bits mode (with Dart integers limited to 64
bits) Bigints are banned and should not be used.
This CL revises Dart_IntegerToHexCString implementation to avoid
creating Bigint objects for Smi and Mint arguments, so it would
work in --limit-ints-to-64-bits mode.

Also, this CL adds test case to lock down the behavior of
Dart_IntegerToHexCString.

Issue: https://github.com/dart-lang/sdk/issues/30103
==========

to

==========
[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

Until this change, implementation of Dart_IntegerToHexCString()
always created Bigint objects and used Bigint::ToHexCString() to do
the work.

In --limit-ints-to-64-bits mode (with Dart integers limited to 64
bits) Bigints are banned and should not be used.
This CL revises Dart_IntegerToHexCString implementation to avoid
creating Bigint objects for Smi and Mint arguments, so it would
work in --limit-ints-to-64-bits mode.

Also, this CL adds test case to lock down the behavior of
Dart_IntegerToHexCString.

R=asiva@google.com

Issue: https://github.com/dart-lang/sdk/issues/30103
Committed:
https://github.com/dart-lang/sdk/commit/3d4838fc70a5439437a5ceb4247551315c294477
==========

[alexmarkov, 2017-08-01 16:00:45]

Committed patchset #2 (id:20001) manually as
3d4838fc70a5439437a5ceb4247551315c294477 (presubmit successful).

[zra, 2017-08-01 16:21:57]

https://codereview.chromium.org/2987183002/diff/20001/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/2987183002/diff/20001/runtime/vm/object.cc#ne...
runtime/vm/object.cc:18245: return OS::SCreate(zone, "-0x%" PRIX64,
static_cast<uint64_t>(-value));
We have some abbreviations for these here:

https://github.com/dart-lang/sdk/blob/master/runtime/platform/globals.h#L390

Also, I think they have to be followed by "", so:

OS::SCreate(zone, "-0x%" Px64 "", ...)

[alexmarkov, 2017-08-01 17:40:11]

https://codereview.chromium.org/2987183002/diff/20001/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/2987183002/diff/20001/runtime/vm/object.cc#ne...
runtime/vm/object.cc:18245: return OS::SCreate(zone, "-0x%" PRIX64,
static_cast<uint64_t>(-value));
On 2017/08/01 16:21:57, zra wrote:
> We have some abbreviations for these here:
> 
> https://github.com/dart-lang/sdk/blob/master/runtime/platform/globals.h#L390

Introduced new short form specifier PX64, see
https://codereview.chromium.org/2985423002/


> 
> Also, I think they have to be followed by "", so:
> 
> OS::SCreate(zone, "-0x%" Px64 "", ...)

I think there is no need in trailing "", because these format specifier
constants are just string literals like "d" or "llx". Can you clarify why
appending an empty string at the end is useful?