[llvm] [SPIR-V] Complete SPV_INTEL_16bit_atomics extension support (PR #184312)

[Viktoria Maximova via llvm-commits]

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@@ -1622,10 +1622,44 @@ void addInstrRequirements(const MachineInstr &MI,
     assert(InstrPtr->getOperand(1).isReg() && "Unexpected operand in atomic");
     Register TypeReg = InstrPtr->getOperand(1).getReg();
     SPIRVTypeInst TypeDef = MRI.getVRegDef(TypeReg);
+    unsigned Op = MI.getOpcode();
+
     if (TypeDef->getOpcode() == SPIRV::OpTypeInt) {
       unsigned BitWidth = TypeDef->getOperand(1).getImm();
       if (BitWidth == 64)
         Reqs.addCapability(SPIRV::Capability::Int64Atomics);
+      else if (BitWidth == 16) {
+        if (!ST.canUseExtension(SPIRV::Extension::SPV_INTEL_16bit_atomics))
+          report_fatal_error(
+              "16-bit integer atomic operations require the following SPIR-V "
+              "extension: SPV_INTEL_16bit_atomics",
+              false);
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vmaksimo wrote:

I believe the situation without extension is the same for [Vulkan environment](https://docs.vulkan.org/guide/latest/atomics.html#_baseline_support) as well.
> With Vulkan 1.0 and no extensions, an application is allowed to use 32-bit int type for atomics.

Are we aware of other envs which can have the different approach here?

https://github.com/llvm/llvm-project/pull/184312