RFR: 8308975: Fix signed integer overflow in compiler code, part 2 [v2]

[Coleen Phillimore]

On Tue, 30 May 2023 17:38:41 GMT, Dean Long <dlong at openjdk.org> wrote:

>> This is a followup from part 1.  I had to use java_add/subtract/multiply/negate in a few more places.
>> cpu_loads_process had an overflow on BSD when the first snapshot is relative to the epoch in 1970.
>> Use unsigned for C2 Type hash functions.
>
> Dean Long has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - use uint64_t for nanos
>  - fix alignment

There's one cast that I think you should fix.

src/hotspot/share/opto/type.cpp line 2279:

> 2277:   for( uint i=0; i<_cnt; i++ )
> 2278:     sum += (uintptr_t)_fields[i];     // Hash on pointers directly
> 2279:   return sum;

This looks like it's going to get a -Wconversion warning if we had them on - I think "sum" needs to be cast to uint.

src/hotspot/share/opto/type.cpp line 2579:

> 2577: // Type-specific hashing function.
> 2578: uint TypeVect::hash(void) const {
> 2579:   return (uint)(uintptr_t)_elem + (uint)(uintptr_t)_length;

I think you might want (uint)((uintptr_t)_elem + _length);  I think _length will promote to the uintptr_t from its declared type uint without warning.

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PR Review: https://git.openjdk.org/jdk/pull/14188#pullrequestreview-1451804079
PR Review Comment: https://git.openjdk.org/jdk/pull/14188#discussion_r1210814371
PR Review Comment: https://git.openjdk.org/jdk/pull/14188#discussion_r1210817567