[llvm] Add support for NSDI DebugLine and DebugNoLine. (PR #215851)

[Manuel Carrasco via llvm-commits]

================
@@ -1157,6 +1187,92 @@ void SPIRVNonSemanticDebugHandler::endFunctionImpl(const MachineFunction *MF) {
 void SPIRVNonSemanticDebugHandler::beginInstruction(const MachineInstr *MI) {
   assert(CurMI == nullptr && "CurMI must be null");
   CurMI = MI;
+
+  if (!DebugFunctionDefinitionEmitted)
+    return;
+  emitDebugLineForInstruction(MI);
+}
+
+static bool isDebugLineTarget(const MachineInstr *MI,
+                              SPIRV::ModuleAnalysisInfo &MAI) {
+  if (MAI.getSkipEmission(MI))
+    return false;
+  switch (MI->getOpcode()) {
+  case SPIRV::OpFunction:
+  case SPIRV::OpFunctionParameter:
+  case SPIRV::OpFunctionEnd:
+  case SPIRV::OpLabel:
+    return false;
+  default:
+    return true;
+  }
+}
+
+void SPIRVNonSemanticDebugHandler::emitDebugLineForInstruction(
+    const MachineInstr *MI) {
+  assert(DebugFunctionDefinitionEmitted &&
+         "DebugFunctionDefinition must be emitted");
+  assert(CurrentMAI && "CurrentMAI must be set");
+
+  SPIRV::ModuleAnalysisInfo &MAI = *CurrentMAI;
+
+  // Structural opcodes don't require a DebugLine, other opcodes might have
+  // already been emitted in the module scope.
+  if (!isDebugLineTarget(MI, MAI))
+    return;
+
+  // The range of DebugLine must be reset at each basic block boundary.
+  if (LastLineMI && MI->getParent() != LastLineMI->getParent())
+    LastLineMI = nullptr;
+
+  MCRegister VoidTypeReg = getOrEmitOpTypeVoidReg(MAI);
+  MCRegister ExtInstSetReg = MAI.getExtInstSetReg(NSSet);
+
+  const DILocation *DL = MI->getDebugLoc().get();
+  if (!DL) {
+    // No location for the current instruction
+    if (LastLineMI) {
+      // Close the current DebugLine region.
+      emitExtInst(SPIRV::NonSemanticExtInst::DebugNoLine, VoidTypeReg,
+                  ExtInstSetReg, {}, MAI);
+      LastLineMI = nullptr;
+    }
+    // No DebugLine region to close.
+    return;
+  }
+
+  // At this point, there is a location for the current instruction.
+  // If it matches the last emitted DebugLine, no new DebugLine region is
+  // needed. Otherwise, emit a new DebugLine region and update LastLineMI.
+
+  MCRegister FileStrReg = getCachedScopePathOpStringReg(
+      DL->getScope(), /*UseEmptyPathIfNullScope=*/true);
+  unsigned Line = DL->getLine();
+  unsigned Col = DL->getColumn();
+
+  MCRegister SrcReg = DebugSourceRegByFileStr.lookup(FileStrReg.id());
+  MCRegister LineReg = I32ConstantCache.lookup(Line);
+  MCRegister ColStartReg = I32ConstantCache.lookup(Col);
+  MCRegister ColEndReg = I32ConstantCache.lookup(Col + 1);
----------------
mgcarrasco wrote:

Sorry, I should've clarified this. I did this mainly to avoid divergences with the SPIRV-LLVM Translator (it does the same).

> Any plans to refine it later with the token's actual width? 

Just to learn, is that something that is already computed or easy to retrieve? Would it require changes in the frontend? I'd like to keep it simple for now so we can move forward with the remaining opcodes. I'm in favour to improve its accuracy later.

https://github.com/llvm/llvm-project/pull/215851