Add the following flags to `wgpu_types::Features`:
- `SHADER_INT64_ATOMIC_ALL_OPS` enables all atomic operations on `atomic<i64>` and
`atomic<u64>` values.
- `SHADER_INT64_ATOMIC_MIN_MAX` is a subset of the above, enabling only
`AtomicFunction::Min` and `AtomicFunction::Max` operations on `atomic<i64>` and
`atomic<u64>` values in the `Storage` address space. These are the only 64-bit
atomic operations available on Metal as of 3.1.
Add corresponding flags to `naga::valid::Capabilities`. These are supported by the
WGSL front end, and all Naga backends.
Platform support:
- On Direct3d 12, in `D3D12_FEATURE_DATA_D3D12_OPTIONS9`, if
`AtomicInt64OnTypedResourceSupported` and `AtomicInt64OnGroupSharedSupported` are
both available, then both wgpu features described above are available.
- On Metal, `SHADER_INT64_ATOMIC_MIN_MAX` is available on Apple9 hardware, and on
hardware that advertises both Apple8 and Mac2 support. This also requires Metal
Shading Language 2.4 or later. Metal does not yet support the more general
`SHADER_INT64_ATOMIC_ALL_OPS`.
- On Vulkan, if the `VK_KHR_shader_atomic_int64` extension is available with both the
`shader_buffer_int64_atomics` and `shader_shared_int64_atomics` features, then both
wgpu features described above are available.
Add tests to ensure that validation checks that `CallResult` and
`AtomicResult` expressions actually have their values provided by
`Call` and `Atomic` statements, and not `Emit` statements.
