[llvm] [SPIRV] Fix enqueue empty kernel (PR #187671)

[via llvm-commits]

================
@@ -2797,85 +2794,137 @@ getOrCreateSPIRVDeviceEventPointer(MachineIRBuilder &MIRBuilder,
 static bool buildEnqueueKernel(const SPIRV::IncomingCall *Call,
                                MachineIRBuilder &MIRBuilder,
                                SPIRVGlobalRegistry *GR) {
+  // In this function there are three stages:
+  //   1. prepare call indexes in order we expect them.
+  //   2. process all arguments which requered preparation.
+  //   3. create a SPIRV operator with arguments.
+
   MachineRegisterInfo *MRI = MIRBuilder.getMRI();
   const DataLayout &DL = MIRBuilder.getDataLayout();
-  bool IsSpirvOp = Call->isSpirvOp();
-  bool HasEvents = Call->Builtin->Name.contains("events") || IsSpirvOp;
   const SPIRVTypeInst Int32Ty = GR->getOrCreateSPIRVIntegerType(32, MIRBuilder);
 
-  // Make vararg instructions before OpEnqueueKernel.
-  // Local sizes arguments: Sizes of block invoke arguments. Clang generates
-  // local size operands as an array, so we need to unpack them.
+  // 1. prepare call indexes in order we expect them.
+  // Based on clang sources, clang/lib/CodeGen/CGBuiltin.cpp, BIenqueue_kernel,
+  // We expect 4 different layouts of call arguments:
+  //   1) No events, no vargs: {Queue, Flags, Range, Kernel, Block};
+  //   2) No events, varargs: {Queue, Flags, Range, Kernel, Block, NumElem,
+  //      ElemPtr};
+  //   3) events, no varargs: {Queue, Flags, Range, NumEvents,
+  //      EventWaitList, EventRet, Kernel, Block};
+  //   4) events, varargs: {Queue,
+  //      Flags, Range, NumEvents, EventWaitList, EventRet, Kernel, Block,
+  //      NumElem, ElemPtr};
+  //
+  // We also may expect __spirv_EnqueueKernel
+  /// TODO: handle __spirv_EnqueueKernel
----------------
idubinov wrote:

TODO removed, as this case already covered by the code. Test case added

https://github.com/llvm/llvm-project/pull/187671