[llvm] [SPIRV] Emitting DebugSource, DebugCompileUnit (PR #97558)

[via llvm-commits]

================
@@ -0,0 +1,148 @@
+#include "MCTargetDesc/SPIRVBaseInfo.h"
+#include "SPIRVGlobalRegistry.h"
+#include "SPIRVRegisterInfo.h"
+#include "SPIRVTargetMachine.h"
+#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineOperand.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;
+  SPIRVTargetMachine *TM;
+  SPIRVEmitNonSemanticDI(SPIRVTargetMachine *TM);
+  SPIRVEmitNonSemanticDI();
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+private:
+  bool IsGlobalDIEmitted = false;
+  bool emitGlobalDI(MachineFunction &MF);
+};
+
+void initializeSPIRVEmitNonSemanticDIPass(PassRegistry &);
+
+FunctionPass *createSPIRVEmitNonSemanticDIPass(SPIRVTargetMachine *TM) {
+  return new SPIRVEmitNonSemanticDI(TM);
+}
+} // 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(SPIRVTargetMachine *TM)
+    : MachineFunctionPass(ID), TM(TM) {
+  initializeSPIRVEmitNonSemanticDIPass(*PassRegistry::getPassRegistry());
+}
+
+SPIRVEmitNonSemanticDI::SPIRVEmitNonSemanticDI() : MachineFunctionPass(ID) {
+  initializeSPIRVEmitNonSemanticDIPass(*PassRegistry::getPassRegistry());
+}
+
+bool SPIRVEmitNonSemanticDI::emitGlobalDI(MachineFunction &MF) {
+  MachineModuleInfo &MMI = MF.getMMI();
+  const Module *M = MMI.getModule();
+  NamedMDNode *DbgCu = M->getNamedMetadata("llvm.dbg.cu");
+  if (!DbgCu) {
+    return false;
+  }
+  std::string FilePath;
+  unsigned SourceLanguage;
+  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();
+      SourceLanguage = CompileUnit->getSourceLanguage();
+    }
+  }
+  NamedMDNode *ModuleFlags = M->getNamedMetadata("llvm.module.flags");
+  int64_t DwarfVersion = 0;
+  int64_t DebugInfoVersion = 0;
+  for (auto *Op : ModuleFlags->operands()) {
+    const MDOperand &StrOp = Op->getOperand(1);
+    if (StrOp.equalsStr("Dwarf Version")) {
----------------
bwlodarcz wrote:

Nice suggestion but there is one 'but' here.
```
!llvm.module.flags = !{!2, !3, !4, !5}
!2 = !{i32 7, !"Dwarf Version", i32 5}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = !{i32 1, !"wchar_size", i32 4}
!5 = !{i32 7, !"frame-pointer", i32 2}
```
The proposed change will unfortunately make a cast to value for everything in `llvm.module.flags` in operand second position. If it isn't i32 constant then it will crash. I'm not sure every possible combination of that metadata so defensibly assigned cast only when first operand is String with correct name. 

https://github.com/llvm/llvm-project/pull/97558