[SPIRV] Added new stub pass for NonSemantic DI

The commit adds new empty pass for emission of
NonSemantic.Shader.DebugInfo.100 instructions.
The pass is a basis for future development and
can be (and likely will be) a subject of change.
In addition to that there is additional unused function
which main purpose is to be basis of accessing global
metadata which is inaccessible in MIR. Accessing such
metadata is necessary for emitting such instructions
like DebugCompilationUnit or DebugSource.

Author: bwlodarcz

llvm/lib/Target/SPIRV/CMakeLists.txt

@@ -40,6 +40,7 @@ add_llvm_target(SPIRVCodeGen
   SPIRVSubtarget.cpp
   SPIRVTargetMachine.cpp
   SPIRVUtils.cpp
+  SPIRVEmitNonSemanticDI.cpp
 
   LINK_COMPONENTS
   Analysis

llvm/lib/Target/SPIRV/SPIRV.h

@@ -26,6 +26,7 @@ FunctionPass *createSPIRVRegularizerPass();
 FunctionPass *createSPIRVPreLegalizerPass();
 FunctionPass *createSPIRVPostLegalizerPass();
 ModulePass *createSPIRVEmitIntrinsicsPass(SPIRVTargetMachine *TM);
+MachineFunctionPass *createSPIRVEmitNonSemanticDIPass();
 InstructionSelector *
 createSPIRVInstructionSelector(const SPIRVTargetMachine &TM,
                                const SPIRVSubtarget &Subtarget,
@@ -36,6 +37,7 @@ void initializeSPIRVConvergenceRegionAnalysisWrapperPassPass(PassRegistry &);
 void initializeSPIRVPreLegalizerPass(PassRegistry &);
 void initializeSPIRVPostLegalizerPass(PassRegistry &);
 void initializeSPIRVEmitIntrinsicsPass(PassRegistry &);
+void initializeSPIRVEmitNonSemanticDIPass(PassRegistry &);
 } // namespace llvm
 
 #endif // LLVM_LIB_TARGET_SPIRV_SPIRV_H

llvm/lib/Target/SPIRV/SPIRVEmitNonSemanticDI.cpp

@@ -0,0 +1,55 @@
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/PassRegistry.h"
+#include "llvm/Support/Casting.h"
+
+namespace llvm {
+struct SPIRVEmitNonSemanticDI : public MachineFunctionPass {
+  static char ID;
+  SPIRVEmitNonSemanticDI();
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+};
+
+void initializeSPIRVEmitNonSemanticDIPass(PassRegistry &);
+
+FunctionPass *createSPIRVEmitNonSemanticDIPass() {
+  return new SPIRVEmitNonSemanticDI();
+}
+} // namespace llvm
+
+using namespace llvm;
+
+INITIALIZE_PASS(SPIRVEmitNonSemanticDI, "spirv-nonsemantic-debug-info",
+                "SPIRV NonSemantic.Shader.DebugInfo.100 emitter", false, false)
+
+char SPIRVEmitNonSemanticDI::ID = 0;
+
+SPIRVEmitNonSemanticDI::SPIRVEmitNonSemanticDI() : MachineFunctionPass(ID) {
+  initializeSPIRVEmitNonSemanticDIPass(*PassRegistry::getPassRegistry());
+}
+
+[[maybe_unused]]
+static void findCompileUnitDI(const MachineFunction &MF) {
+  MachineModuleInfo &MMI = MF.getMMI();
+  const Module *M = MMI.getModule();
+  NamedMDNode *DbgCu = M->getNamedMetadata("llvm.dbg.cu");
+  std::string FilePath;
+  if (DbgCu) {
+    unsigned NumOp = DbgCu->getNumOperands();
+    if (NumOp) {
+      if (const auto *CompileUnit =
+              dyn_cast<DICompileUnit>(DbgCu->getOperand(0))) {
+        DIFile *File = CompileUnit->getFile();
+        FilePath = ((File->getDirectory() + "/" + File->getFilename())).str();
+      }
+    }
+  }
+}
+
+bool SPIRVEmitNonSemanticDI::runOnMachineFunction(MachineFunction &MF) {
+  return false;
+}

llvm/lib/Target/SPIRV/SPIRVTargetMachine.cpp

@@ -199,6 +199,7 @@ void SPIRVPassConfig::addPreLegalizeMachineIR() {
 bool SPIRVPassConfig::addLegalizeMachineIR() {
   addPass(new Legalizer());
   addPass(createSPIRVPostLegalizerPass());
+  addPass(createSPIRVEmitNonSemanticDIPass());
   return false;
 }