JDK-8160748: inconsistent types for ideal_reg

[Kim Barrett]

[re-replying on the hotspot-compiler-dev list, as my original reply was in a related hotspot-dev thread.]

> On Jul 3, 2016, at 10:54 AM, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
> 
> Hi all,
> 
> We've worked for JDK-8160353 to resolve narrowing conversion error at GCC 6.
> ------------
> /home/ysuenaga/OpenJDK/hs/hotspot/src/share/vm/opto/type.cpp:101:1: error: narrowing conversion of '(uint)Node::NotAMachineReg' from 'uint {aka unsigned int}' to 'int' inside { } [-Werror=narrowing]
> };
> ^
> /home/ysuenaga/OpenJDK/hs/hotspot/src/share/vm/opto/type.cpp:101:1: error: narrowing conversion of '(uint)Node::NotAMachineReg' from 'uint {aka unsigned int}' to 'int' inside { } [-Werror=narrowing]
> /home/ysuenaga/OpenJDK/hs/hotspot/src/share/vm/opto/type.cpp:101:1: error: narrowing conversion of '(uint)Node::NotAMachineReg' from 'uint {aka unsigned int}' to 'int' inside { } [-Werror=narrowing]
> cc1plus: all warnings being treated as errors
> ------------
> 
> Opcodes is defined as enum.
> However, a part of code (e.g. NotAMachineReg) is defined as uint.
> 
> I think Opcodes related code should consist uint type.
> 
>  http://cr.openjdk.java.net/~ysuenaga/JDK-8160748/webrev.00/
> 
> I've uploaded webrev for this issue.
> I fixed Opcodes type to uint at first, and fixed many errors with GCC 6.
> 
> I want to discuss about this.
> 
> 
> Thanks,
> 
> Yasumasa

I’m not going to review that, but I took a very brief look and:

---------------
src/share/vm/opto/opcodes.hpp
 30 enum Opcodes : uint {

This is not valid C++98 code.  It is using a C++11 feature, e.g. specifying the underlying type
of an enum.

---------------

My intent in separating JDK-8160748 from JDK-8160353 was to allow the remainder of the latter
to be fixed now, and JDK-8160748  to be dealt with later, probably not in JDK 9 at all, since the
implicit narrowing is not a problem with C++98.