llvm-undname: Several behavior-preserving changes to increase coverage

- Replace `Error = true` in a few branches that are truly unreachable
  with DEMANGLE_UNREACHABLE

- Remove early return early in startsWithLocalScopePattern() because
  it's redundant with the next two early returns

- Remove unreachable `case '0'` (it's handled in the branch below)

- Remove an unused bool return

- Add test coverage for several early error returns, mostly in
  array type parsing

llvm-svn: 362506

2 files changed, 10 insertions, 16 deletions

diff --git a/llvm/lib/Demangle/MicrosoftDemangle.cpp b/llvm/lib/Demangle/MicrosoftDemangle.cpp
index b93a84ea91d..83e6f60de03 100644
--- a/llvm/lib/Demangle/MicrosoftDemangle.cpp
+++ b/llvm/lib/Demangle/MicrosoftDemangle.cpp
@@ -58,8 +58,9 @@ static bool isMemberPointer(StringView MangledName, bool &Error) {
     // what.
     break;
   default:
-    Error = true;
-    return false;
+    // isMemberPointer() is called only if isPointerType() returns true,
+    // and it rejects other prefixes.
+    DEMANGLE_UNREACHABLE;
   }
 
   // If it starts with a number, then 6 indicates a non-member function
@@ -141,8 +142,6 @@ consumeSpecialIntrinsicKind(StringView &MangledName) {
 static bool startsWithLocalScopePattern(StringView S) {
   if (!S.consumeFront('?'))
     return false;
-  if (S.size() < 2)
-    return false;
 
   size_t End = S.find('?');
   if (End == StringView::npos)
@@ -2197,7 +2196,7 @@ Demangler::demangleTemplateParameterList(StringView &MangledName) {
       MangledName = MangledName.dropFront();
       // 1 - single inheritance       <name>
       // H - multiple inheritance     <name> <number>
-      // I - virtual inheritance      <name> <number> <number> <number>
+      // I - virtual inheritance      <name> <number> <number>
       // J - unspecified inheritance  <name> <number> <number> <number>
       char InheritanceSpecifier = MangledName.popFront();
       SymbolNode *S = nullptr;
@@ -2226,8 +2225,7 @@ Demangler::demangleTemplateParameterList(StringView &MangledName) {
       case '1':
         break;
       default:
-        Error = true;
-        break;
+        DEMANGLE_UNREACHABLE;
       }
       TPRN->Affinity = PointerAffinity::Pointer;
       TPRN->Symbol = S;
@@ -2254,12 +2252,9 @@ Demangler::demangleTemplateParameterList(StringView &MangledName) {
             demangleSigned(MangledName);
         TPRN->ThunkOffsets[TPRN->ThunkOffsetCount++] =
             demangleSigned(MangledName);
-        DEMANGLE_FALLTHROUGH;
-      case '0':
         break;
       default:
-        Error = true;
-        break;
+        DEMANGLE_UNREACHABLE;
       }
       TPRN->IsMemberPointer = true;
 
diff --git a/llvm/lib/Demangle/MicrosoftDemangleNodes.cpp b/llvm/lib/Demangle/MicrosoftDemangleNodes.cpp
index c26151c5b19..c07fde897e0 100644
--- a/llvm/lib/Demangle/MicrosoftDemangleNodes.cpp
+++ b/llvm/lib/Demangle/MicrosoftDemangleNodes.cpp
@@ -34,21 +34,20 @@ static void outputSpaceIfNecessary(OutputStream &OS) {
     OS << " ";
 }
 
-static bool outputSingleQualifier(OutputStream &OS, Qualifiers Q) {
+static void outputSingleQualifier(OutputStream &OS, Qualifiers Q) {
   switch (Q) {
   case Q_Const:
     OS << "const";
-    return true;
+    break;
   case Q_Volatile:
     OS << "volatile";
-    return true;
+    break;
   case Q_Restrict:
     OS << "__restrict";
-    return true;
+    break;
   default:
     break;
   }
-  return false;
 }
 
 static bool outputQualifierIfPresent(OutputStream &OS, Qualifiers Q,