[DebugInfo] In GlobalISel, convert llvm.dbg.label to DBG_LABEL MI.

[HsiangKai]

Summary

Convert llvm.dbg.label(!label_metadata) to DBG_LABEL !label_metadata.

include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h

MachineInstrBuilder buildFIDbgValue(int FI, const MDNode *Variable,
                                       const MDNode *Expr);
 
   /// Build and insert a DBG_VALUE instructions specifying that \p Variable is
   /// given by \p C (suitably modified by \p Expr).
   MachineInstrBuilder buildConstDbgValue(const Constant &C,
                                          const MDNode *Variable,
                                          const MDNode *Expr);
 
+  /// Build and insert a DBG_LABEL instructions specifying that \p Label is
+  /// given. Convert "llvm.dbg.label Label" to "DBG_LABEL Label".
+  MachineInstrBuilder buildDbgLabel(const MDNode *Label);
+
   /// Build and insert \p Res = G_FRAME_INDEX \p Idx
   ///
   /// G_FRAME_INDEX materializes the address of an alloca value or other
   /// stack-based object.
   ///
   /// \pre setBasicBlock or setMI must have been called.
   /// \pre \p Res must be a generic virtual register with pointer type.
   ///

lib/CodeGen/GlobalISel/IRTranslator.cpp

if (AI && AI->isStaticAlloca()) {
       // instructions (in fact, they get ignored if they *do* exist).
       MF->setVariableDbgInfo(DI.getVariable(), DI.getExpression(),
                              getOrCreateFrameIndex(*AI), DI.getDebugLoc());
     } else
       MIRBuilder.buildDirectDbgValue(getOrCreateVReg(*Address),
                                      DI.getVariable(), DI.getExpression());
     return true;
   }
+  case Intrinsic::dbg_label: {
+    const DbgLabelInst &DI = cast<DbgLabelInst>(CI);
+    assert(DI.getLabel() && "Missing label");
+
+    assert(DI.getLabel()->isValidLocationForIntrinsic(
+               MIRBuilder.getDebugLoc()) &&
+           "Expected inlined-at fields to agree");
+
+    MIRBuilder.buildDbgLabel(DI.getLabel());
+    return true;
+  }
   case Intrinsic::vaend:
     // No target I know of cares about va_end. Certainly no in-tree target
     // does. Simplest intrinsic ever!
     return true;
   case Intrinsic::vastart: {
     auto &TLI = *MF->getSubtarget().getTargetLowering();
     Value *Ptr = CI.getArgOperand(0);
     unsigned ListSize = TLI.getVaListSizeInBits(*DL) / 8;

lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
   } else {
     // Insert %noreg if we didn't find a usable constant and had to drop it.
     MIB.addReg(0U);
   }
 
   return MIB.addImm(0).addMetadata(Variable).addMetadata(Expr);
 }
 
+MachineInstrBuilder MachineIRBuilder::buildDbgLabel(const MDNode *Label) {
+  assert(isa<DILabel>(Label) && "not a label");
+  assert(cast<DILabel>(Label)->isValidLocationForIntrinsic(DL) &&
+         "Expected inlined-at fields to agree");
+  auto MIB = buildInstr(TargetOpcode::DBG_LABEL);
+
+  return MIB.addMetadata(Label);
+}
+
 MachineInstrBuilder MachineIRBuilder::buildFrameIndex(unsigned Res, int Idx) {
   assert(MRI->getType(Res).isPointer() && "invalid operand type");
   return buildInstr(TargetOpcode::G_FRAME_INDEX)
       .addDef(Res)
       .addFrameIndex(Idx);
 }
 
 MachineInstrBuilder MachineIRBuilder::buildGlobalValue(unsigned Res,