RFR: 8145096: Undefined behaviour in HotSpot

[Kim Barrett]

On Dec 11, 2015, at 2:33 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
>> So, the lvalue cast makes the following macro definition plausible:
>> 
>> #define JAVA_INTEGER_OP(OP, NAME, TYPE, UNSIGNED_TYPE)  \
>> inline TYPE NAME (TYPE in1, TYPE in2) {                 \
>> STATIC_ASSERT(sizeof(TYPE) == sizeof(UNSIGNED_TYPE)); \
>> UNSIGNED_TYPE ures = static_cast<UNSIGNED_TYPE>(in1); \
>> ures OP ## = static_cast<UNSIGNED_TYPE>(in2);         \
>> return reinterpret_cast<TYPE&>(ures);                          \
>> }
> 
> […]
> I'll collect information on other platforms.

I've reviewed the generated code for a bunch of platforms, and this
approach is well supported across the full set when using optimization
levels used to build hotspot.  Thanks to Goetz Lindenmaier from SAP
for providing results for many platforms I can't easily access.