VM: Make more globals constant where easily possible.

VM: Make more globals constant where easily possible.

Remove -fdata-section again from the Linux build configuration: It prevented
some optimizations in gcc and clang - fewer things were recognized as constants.

Add const to pointers/arrays in some places to help compilers with determining
what is a constant.  A common pattern is strlen of a string literal const char*,
or an array of function pointers.

Tested with gcc 4.8.4 / clang 3.4 and improves code qualtiy + reduces binary size.

BUG=
R=iposva@google.com, rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/64e71a0b2e74cbb8a2a840b18fa100007ec1c43f

[Florian Schneider, 2015-11-19 16:09:14]

Description was changed from

==========
VM: Make more globals constant where easily possible.

Remove -fdata-section again from the Linux build configuration: It prevented
some optimizations in gcc and clang - fewer things were recognized as constants.

Add const to pointers/arrays in some places to help compilers with determining
what is a constant.  A common pattern is strlen of a string literal const char*,
or an array of function pointers.

Tested with gcc 4.8.4 / clang 3.4 and improve code qualtiy + reduce binary size.

BUG=
==========

to

==========
VM: Make more globals constant where easily possible.

Remove -fdata-section again from the Linux build configuration: It prevented
some optimizations in gcc and clang - fewer things were recognized as constants.

Add const to pointers/arrays in some places to help compilers with determining
what is a constant.  A common pattern is strlen of a string literal const char*,
or an array of function pointers.

Tested with gcc 4.8.4 / clang 3.4 and improves code qualtiy + reduces binary
size.

BUG=
==========

[Florian Schneider, 2015-11-19 16:17:00]

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

[Florian Schneider, 2015-11-19 16:17:01]

https://codereview.chromium.org/1462953002/diff/1/runtime/vm/globals.h
File runtime/vm/globals.h (right):

https://codereview.chromium.org/1462953002/diff/1/runtime/vm/globals.h#newcode31
runtime/vm/globals.h:31: #define kNegInfinity
bit_cast<double>(DART_UINT64_C(0xfff0000000000000))
This was the only way I could make gcc/clang not create global variables for
these.

So far I found two alternatives:
1. Use C macros HUGE_VAL or INFINITY - these were replaced in a previous CL
(https://codereview.chromium.org//609593002).

2. Use C++11 std::numeric_limits<double>::infinity(), which is a true
compile-time constant.

[rmacnak, 2015-11-20 01:03:57]

lgtm

https://chromiumcodereview.appspot.com/1462953002/diff/1/runtime/vm/globals.h
File runtime/vm/globals.h (right):

https://chromiumcodereview.appspot.com/1462953002/diff/1/runtime/vm/globals.h...
runtime/vm/globals.h:31: #define kNegInfinity
bit_cast<double>(DART_UINT64_C(0xfff0000000000000))
On 2015/11/19 16:17:00, Florian Schneider wrote:
> This was the only way I could make gcc/clang not create global variables for
> these.
> 
> So far I found two alternatives:
> 1. Use C macros HUGE_VAL or INFINITY - these were replaced in a previous CL
> (https://codereview.chromium.org//609593002).

IIRC, we hit an environment where INFINITY was either undefined or the wrong
value.

> 
> 2. Use C++11 std::numeric_limits<double>::infinity(), which is a true
> compile-time constant.
>

[Ivan Posva, 2015-11-20 04:40:51]

LGTM
-Ivan

P.S. As Ryan says INFINITY was not usable as it caused compiler warnings and
other broken behaviour on certain platforms.

[Florian Schneider, 2015-11-20 09:52:12]

Committed patchset #2 (id:20001) manually as
64e71a0b2e74cbb8a2a840b18fa100007ec1c43f (presubmit successful).