[libcxxabi][ItaniumDemangle] Separate GtIsGt counter into more states

Currently `OutputBuffer::GtIsGt` is used to tell us if we're inside template arguments and have printed a '(' without a closing ')'. If so, we don't need to quote '<' when printing it as part of a binary expression inside a template argument. Otherwise we need to. E.g.,
```
foo<a<(b < c)>> // Quotes around binary expression needed.
```

LLDB's `TrackingOutputBuffer` has heuristics that rely on checking whether we are inside template arguments, regardless of the current parentheses depth. We've been using `isGtInsideTemplateArgs` for this, but that isn't correct. Resulting in us incorrectly tracking the basename of function like:
```
void func<(foo::Enum)1>()
```
Here `GtIsGt > 0` despite us being inside template arguments (because we incremented it when seeing '(').

This patch adds a `isInsideTemplateArgs` API which LLDB will use to more accurately track parts of the demangled name.

To make sure this API doesn't go untested in the actual libcxxabi test-suite, I changed the existing `GtIsGt` logic to use it. Also renamed the various variables/APIs involved to make it (in my opinion) more straightforward to understand what's going on. But happy to rename it back if people disagree.

Author: Michael137

libcxxabi/src/demangle/ItaniumDemangle.h

@@ -1366,7 +1366,7 @@ class TemplateTemplateParamDecl final : public Node {
   template <typename Fn> void match(Fn F) const { F(Name, Params, Requires); }
 
   void printLeft(OutputBuffer &OB) const override {
-    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
     OB += "template<";
     Params.printWithComma(OB);
     OB += "> typename ";
@@ -1550,7 +1550,7 @@ class TemplateArgs final : public Node {
   NodeArray getParams() { return Params; }
 
   void printLeft(OutputBuffer &OB) const override {
-    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
     OB += "<";
     Params.printWithComma(OB);
     OB += ">";
@@ -1824,7 +1824,7 @@ class ClosureTypeName : public Node {
 
   void printDeclarator(OutputBuffer &OB) const {
     if (!TemplateParams.empty()) {
-      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
       OB += "<";
       TemplateParams.printWithComma(OB);
       OB += ">";
@@ -1885,7 +1885,9 @@ class BinaryExpr : public Node {
   }
 
   void printLeft(OutputBuffer &OB) const override {
-    bool ParenAll = OB.isGtInsideTemplateArgs() &&
+    // If we're printing a '<' inside of a template argument, and we haven't
+    // yet parenthesized the expression, do so now.
+    bool ParenAll = !OB.isInParensInTemplateArgs() &&
                     (InfixOperator == ">" || InfixOperator == ">>");
     if (ParenAll)
       OB.printOpen();
@@ -2061,7 +2063,7 @@ class CastExpr : public Node {
   void printLeft(OutputBuffer &OB) const override {
     OB += CastKind;
     {
-      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
       OB += "<";
       OB.printLeft(*To);
       OB += ">";

libcxxabi/src/demangle/Utility.h

@@ -104,18 +104,32 @@ class OutputBuffer {
   unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
   unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
 
-  /// When zero, we're printing template args and '>' needs to be parenthesized.
-  /// Use a counter so we can simply increment inside parentheses.
-  unsigned GtIsGt = 1;
+  struct {
+    /// The depth of '(' and ')' inside the currently printed template
+    /// arguments.
+    unsigned ParenDepth = 0;
 
-  bool isGtInsideTemplateArgs() const { return GtIsGt == 0; }
+    /// True if we're currently printing a template argument.
+    bool InsideTemplate = false;
+  } TemplateTracker;
+
+  /// Returns true if we're currently between a '(' and ')' when printing
+  /// template args.
+  bool isInParensInTemplateArgs() const {
+    return TemplateTracker.ParenDepth > 0;
+  }
+
+  /// Returns true if we're printing template args.
+  bool isInsideTemplateArgs() const { return TemplateTracker.InsideTemplate; }
 
   void printOpen(char Open = '(') {
-    GtIsGt++;
+    if (isInsideTemplateArgs())
+      TemplateTracker.ParenDepth++;
     *this += Open;
   }
   void printClose(char Close = ')') {
-    GtIsGt--;
+    if (isInsideTemplateArgs())
+      TemplateTracker.ParenDepth--;
     *this += Close;
   }
 

llvm/include/llvm/Demangle/ItaniumDemangle.h

@@ -1366,7 +1366,7 @@ class TemplateTemplateParamDecl final : public Node {
   template <typename Fn> void match(Fn F) const { F(Name, Params, Requires); }
 
   void printLeft(OutputBuffer &OB) const override {
-    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
     OB += "template<";
     Params.printWithComma(OB);
     OB += "> typename ";
@@ -1550,7 +1550,7 @@ class TemplateArgs final : public Node {
   NodeArray getParams() { return Params; }
 
   void printLeft(OutputBuffer &OB) const override {
-    ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+    ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
     OB += "<";
     Params.printWithComma(OB);
     OB += ">";
@@ -1824,7 +1824,7 @@ class ClosureTypeName : public Node {
 
   void printDeclarator(OutputBuffer &OB) const {
     if (!TemplateParams.empty()) {
-      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
       OB += "<";
       TemplateParams.printWithComma(OB);
       OB += ">";
@@ -1885,7 +1885,9 @@ class BinaryExpr : public Node {
   }
 
   void printLeft(OutputBuffer &OB) const override {
-    bool ParenAll = OB.isGtInsideTemplateArgs() &&
+    // If we're printing a '<' inside of a template argument, and we haven't
+    // yet parenthesized the expression, do so now.
+    bool ParenAll = !OB.isInParensInTemplateArgs() &&
                     (InfixOperator == ">" || InfixOperator == ">>");
     if (ParenAll)
       OB.printOpen();
@@ -2061,7 +2063,7 @@ class CastExpr : public Node {
   void printLeft(OutputBuffer &OB) const override {
     OB += CastKind;
     {
-      ScopedOverride<unsigned> LT(OB.GtIsGt, 0);
+      ScopedOverride<bool> LT(OB.TemplateTracker.InsideTemplate, true);
       OB += "<";
       OB.printLeft(*To);
       OB += ">";

llvm/include/llvm/Demangle/Utility.h

@@ -104,18 +104,32 @@ class OutputBuffer {
   unsigned CurrentPackIndex = std::numeric_limits<unsigned>::max();
   unsigned CurrentPackMax = std::numeric_limits<unsigned>::max();
 
-  /// When zero, we're printing template args and '>' needs to be parenthesized.
-  /// Use a counter so we can simply increment inside parentheses.
-  unsigned GtIsGt = 1;
+  struct {
+    /// The depth of '(' and ')' inside the currently printed template
+    /// arguments.
+    unsigned ParenDepth = 0;
 
-  bool isGtInsideTemplateArgs() const { return GtIsGt == 0; }
+    /// True if we're currently printing a template argument.
+    bool InsideTemplate = false;
+  } TemplateTracker;
+
+  /// Returns true if we're currently between a '(' and ')' when printing
+  /// template args.
+  bool isInParensInTemplateArgs() const {
+    return TemplateTracker.ParenDepth > 0;
+  }
+
+  /// Returns true if we're printing template args.
+  bool isInsideTemplateArgs() const { return TemplateTracker.InsideTemplate; }
 
   void printOpen(char Open = '(') {
-    GtIsGt++;
+    if (isInsideTemplateArgs())
+      TemplateTracker.ParenDepth++;
     *this += Open;
   }
   void printClose(char Close = ')') {
-    GtIsGt--;
+    if (isInsideTemplateArgs())
+      TemplateTracker.ParenDepth--;
     *this += Close;
   }