Emit 0 instead of incomplete information

Author: arsenm

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

@@ -903,18 +903,18 @@ void CodeViewDebug::emitCompilerInformation() {
   OS.AddComment("CPUType");
   OS.emitInt16(static_cast<uint64_t>(TheCPU));
 
+  StringRef CompilerVersion = "0";
   auto CUs = MMI->getModule()->debug_compile_units();
-  if (CUs.empty())
-    return;
-
-  const MDNode *Node = *CUs.begin();
-  const auto *CU = cast<DICompileUnit>(Node);
+  if (!CUs.empty()) {
+    const MDNode *Node = *CUs.begin();
+    const auto *CU = cast<DICompileUnit>(Node);
 
-  StringRef CompilerVersion = CU->getProducer();
-  Version FrontVer = parseVersion(CompilerVersion);
-  OS.AddComment("Frontend version");
-  for (int N : FrontVer.Part) {
-    OS.emitInt16(N);
+    CompilerVersion = CU->getProducer();
+    Version FrontVer = parseVersion(CompilerVersion);
+    OS.AddComment("Frontend version");
+    for (int N : FrontVer.Part) {
+      OS.emitInt16(N);
+    }
   }
 
   // Some Microsoft tools, like Binscope, expect a backend version number of at

llvm/test/DebugInfo/X86/codeview-empty-dbg-cu-crash.ll

@@ -19,6 +19,13 @@
 ; CHECK-NEXT: .short	4412                            # Record kind: S_COMPILE3
 ; CHECK-NEXT: .long	3                               # Flags and language
 ; CHECK-NEXT: .short	208                             # CPUType
+; CHECK-NEXT: .short	22000                           # Backend version
+; CHECK-NEXT: .short	0
+; CHECK-NEXT: .short	0
+; CHECK-NEXT: .short	0
+; CHECK-NEXT: .asciz	"0"                             # Null-terminated compiler version string
+; CHECK-NEXT: .p2align	2, 0x0
+; CHECK-NEXT: .Ltmp5:
 ; CHECK-NEXT: .Ltmp1:
 ; CHECK-NEXT: .p2align	2, 0x0
 ; CHECK-NEXT: .cv_filechecksums                       # File index to string table offset subsection