[MTLDevice setShouldMaximizeConcurrentCompilation:YES] crashes on macOS 26 for AMD GPUs

[mrpippy]

This isn't a MoltenVK bug per-se, but FYI: anyone enabling shouldMaximizeConcurrentCompilation is going to see crashes on macOS 26 systems with AMD GPUs. Apple knows about the bug and I expect it will be fixed soon, but not for the 26.0 release on Monday.

The impact of this isn't huge, there's only 3 Intel Macs that even support Tahoe (2019 Mac Pro, 2019 MacBook Pro 16", 2020 MacBook Pro 13" (Four Thunderbolt 3 ports) and only 2 of those have AMD GPUs.

Basically, calling setShouldMaximizeConcurrentCompilation:YES for an AMD GPU MTLDevice will crash.

Backtrace from the Cube demo (but this is reproducible in a trivial standalone app as well):

Thread 0 Crashed:
0   Metal                         	    0x7ff8244d5d5e -[_MTLDevice updateCompilerProcessesCount:] + 26
1   Metal                         	    0x7ff8244d5a8c __53-[_MTLDevice setShouldMaximizeConcurrentCompilation:]_block_invoke + 56
2   libdispatch.dylib             	    0x7ff8180e5bee _dispatch_client_callout + 6
3   libdispatch.dylib             	    0x7ff8180dc8e0 _dispatch_lane_barrier_sync_invoke_and_complete + 60
4   Metal                         	    0x7ff8244d5a4e -[_MTLDevice setShouldMaximizeConcurrentCompilation:] + 75
5   MoltenVK                      	       0x100e33ba4 MVKPhysicalDevice::initMTLDevice() + 132
6   MoltenVK                      	       0x100e33972 MVKPhysicalDevice::MVKPhysicalDevice(MVKInstance*, id<MTLDevice>) + 162
7   MoltenVK                      	       0x100dcd9d6 MVKInstance::MVKInstance(VkInstanceCreateInfo const*) + 1334
8   MoltenVK                      	       0x100db2b48 vkCreateInstance + 56
9   Cube                          	       0x100245429 demo_init_vk + 1386 (cube.c:4204) [inlined]
10  Cube                          	       0x100245429 demo_init + 2058 (cube.c:4876) [inlined]
11  Cube                          	       0x100245429 demo_main + 2105 (cube.c:4986)