working on jump table labels

PR feedback, style

Author: sivadeilra

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

@@ -3566,15 +3566,34 @@ void CodeViewDebug::collectDebugInfoForJumpTables(const MachineFunction *MF,
           break;
         }
 
-        CurFn->JumpTables.push_back(
-            {EntrySize, Base, BaseOffset, Branch,
-             MF->getJTISymbol(JumpTableIndex, MMI->getContext()),
-             JTI.getJumpTables()[JumpTableIndex].MBBs.size()});
+        const MachineJumpTableEntry &JTE = JTI.getJumpTables()[JumpTableIndex];
+        JumpTableInfo CVJTI{EntrySize,
+                            Base,
+                            BaseOffset,
+                            Branch,
+                            MF->getJTISymbol(JumpTableIndex, MMI->getContext()),
+                            JTE.MBBs.size()};
+        for (const auto &MBB : JTE.MBBs)
+          CVJTI.Cases.push_back(MBB->getSymbol());
+        CurFn->JumpTables.push_back(std::move(CVJTI));
       });
 }
 
 void CodeViewDebug::emitDebugInfoForJumpTables(const FunctionInfo &FI) {
-  for (auto JumpTable : FI.JumpTables) {
+  // Emit S_LABEL32 records for each jump target
+  for (const auto &JumpTable : FI.JumpTables) {
+    for (const auto &CaseSym : JumpTable.Cases) {
+      MCSymbol *LabelEnd = beginSymbolRecord(SymbolKind::S_LABEL32);
+      OS.AddComment("Offset and segment");
+      OS.emitCOFFSecRel32(CaseSym, 0);
+      OS.AddComment("Flags");
+      OS.emitInt8(0);
+      emitNullTerminatedSymbolName(OS, CaseSym->getName());
+      endSymbolRecord(LabelEnd);
+    }
+  }
+
+  for (const auto &JumpTable : FI.JumpTables) {
     MCSymbol *JumpTableEnd = beginSymbolRecord(SymbolKind::S_ARMSWITCHTABLE);
     if (JumpTable.Base) {
       OS.AddComment("Base offset");

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h

@@ -146,6 +146,7 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
     const MCSymbol *Branch;
     const MCSymbol *Table;
     size_t TableSize;
+    std::vector<const MCSymbol *> Cases;
   };
 
   // For each function, store a vector of labels to its instructions, as well as

llvm/test/DebugInfo/COFF/jump-table.ll

@@ -118,6 +118,15 @@
 ; CV:         GlobalProcIdSym {
 ; CV:           DisplayName: func
 ; CV-NOT:     GlobalProcIdSym
+; CV:           LabelSym {
+; CV-NEXT:        Kind: S_LABEL32 (0x1105)
+; CV-NEXT:        CodeOffset: 0xC0
+; CV-NEXT:        Segment: 0x0
+; CV-NEXT:        Flags: 0x0
+; CV-NEXT:        Flags [ (0x0)
+; CV-NEXT:        ]
+; CV-NEXT:        DisplayName:
+; CV-NEXT:      }
 ; CV:           JumpTableSym {
 ; CV-NEXT:        Kind: S_ARMSWITCHTABLE (0x1159)
 ; CV-NEXT:        BaseOffset: 0x0