[llvm] [SPIR-V] Support `nonuniformindex` intrsinsic in SPIRV CodeGen. (PR #162540)

[Steven Perron via llvm-commits]

================
@@ -3713,6 +3721,58 @@ bool SPIRVInstructionSelector::selectResourceGetPointer(
       .constrainAllUses(TII, TRI, RBI);
 }
 
+bool SPIRVInstructionSelector::selectResourceNonUniformIndex(
+    Register &ResVReg, const SPIRVType *ResType, MachineInstr &I) const {
+  Register ObjReg = I.getOperand(2).getReg();
+  if (!BuildCOPY(ResVReg, ObjReg, I))
+    return false;
+
+  buildOpDecorate(ResVReg, I, TII, SPIRV::Decoration::NonUniformEXT, {});
+  // Check for the registers that use the index marked as non-uniform
+  // and recursively mark them as non-uniform.
+  // Per the spec, it's necessary that the final argument used for
+  // load/store/sample/atomic must be decorated, so we need to propagate the
+  // decoration through access chains and copies.
+  // https://docs.vulkan.org/samples/latest/samples/extensions/descriptor_indexing/README.html#_when_to_use_non_uniform_indexing_qualifier
+  recursivelyDecorateChildAsNonUniform(ResVReg, ResType, I);
+  return true;
+}
+
+void SPIRVInstructionSelector::recursivelyDecorateChildAsNonUniform(
+    Register &NonUniformReg, const SPIRVType *RegType, MachineInstr &I) const {
+  std::vector<std::tuple<Register, const SPIRVType *, MachineInstr *>> WorkList;
+  bool isDecorated = false;
----------------
s-perron wrote:

```suggestion
  bool IsDecorated = false;
```

https://github.com/llvm/llvm-project/pull/162540