3 files changed, 89 insertions, 2 deletions

diff --git a/llvm/include/llvm/Support/Debug.h b/llvm/include/llvm/Support/Debug.h
index 924d7b2..6720ef5c 100644
--- a/llvm/include/llvm/Support/Debug.h
+++ b/llvm/include/llvm/Support/Debug.h
@@ -54,6 +54,28 @@ void setCurrentDebugType(const char *Type);
 ///
 void setCurrentDebugTypes(const char **Types, unsigned Count);
 
+/// appendDebugType - Set the current debug type, as if the
+/// -debug-only=CurX,CurY,NewZ option were specified when called with NewZ.
+/// The previous state is tracked, so popAppendedDebugTypes can be called to
+/// restore the previous state. Note that DebugFlag also needs to be set to true
+/// for debug output to be produced.
+///
+void appendDebugType(const char *Type);
+
+/// appendDebugTypes - Set the current debug type, as if the
+/// -debug-only=CurX,CurY,NewX,NewY option were specified when called with
+/// [NewX, NewY]. The previous state is tracked, so popAppendedDebugTypes can be
+/// called to restore the previous state. Note that DebugFlag also needs to be
+/// set to true debug output to be produced.
+///
+void appendDebugTypes(const char **Types, unsigned Count);
+
+/// popAppendedDebugTypes - Restores CurDebugType to the state before the last
+/// call to appendDebugType(s). Asserts and returns if the previous state was
+/// empty or was reset by setCurrentDebugType(s).
+///
+void popAppendedDebugTypes();
+
 /// DEBUG_WITH_TYPE macro - This macro should be used by passes to emit debug
 /// information.  If the '-debug' option is specified on the commandline, and if
 /// this is a debug build, then the code specified as the option to the macro
@@ -77,6 +99,19 @@ void setCurrentDebugTypes(const char **Types, unsigned Count);
 #define DEBUG_WITH_TYPE(TYPE, ...)                                             \
   do {                                                                         \
   } while (false)
+#define appendDebugType(X)                                                     \
+  do {                                                                         \
+    (void)(X);                                                                 \
+  } while (false)
+#define appendDebugTypes(X, N)                                                 \
+  do {                                                                         \
+    (void)(X);                                                                 \
+    (void)(N);                                                                 \
+  } while (false)
+#define popAppendedDebugTypes()                                                \
+  do {                                                                         \
+    ;                                                                          \
+  } while (false)
 #endif
 
 /// This boolean is set to true if the '-debug' command line option
diff --git a/llvm/lib/Support/Debug.cpp b/llvm/lib/Support/Debug.cpp
index 5bb04d0..2582be7 100644
--- a/llvm/lib/Support/Debug.cpp
+++ b/llvm/lib/Support/Debug.cpp
@@ -35,6 +35,9 @@
 #undef isCurrentDebugType
 #undef setCurrentDebugType
 #undef setCurrentDebugTypes
+#undef appendDebugType
+#undef appendDebugTypes
+#undef popAppendedDebugTypes
 
 using namespace llvm;
 
@@ -45,6 +48,32 @@ namespace llvm {
 bool DebugFlag = false;
 
 static ManagedStatic<std::vector<std::string>> CurrentDebugType;
+static ManagedStatic<std::vector<int>> AppendedDebugTypeSizes;
+
+/// Appends to the CurrentDebugState by keeping its old state and adding the
+/// new state.
+void appendDebugTypes(const char **Types, unsigned Count) {
+  AppendedDebugTypeSizes->push_back(CurrentDebugType->size());
+  for (size_t T = 0; T < Count; ++T)
+    CurrentDebugType->push_back(Types[T]);
+}
+
+/// Appends to the CurrentDebugState by keeping its old state and adding the
+/// new state.
+void appendDebugType(const char *Type) { appendDebugTypes(&Type, 1); }
+
+/// Restore to the state before the latest call to appendDebugTypes. This can be
+/// done multiple times.
+void popAppendedDebugTypes() {
+  assert(AppendedDebugTypeSizes->size() > 0 &&
+         "Popping from DebugTypes without any previous appending.");
+
+  if (!AppendedDebugTypeSizes->size())
+    return;
+
+  CurrentDebugType->resize(AppendedDebugTypeSizes->back());
+  AppendedDebugTypeSizes->pop_back();
+}
 
 /// Return true if the specified string is the debug type
 /// specified on the command line, or if none was specified on the command line
@@ -72,6 +101,8 @@ void setCurrentDebugType(const char *Type) {
 }
 
 void setCurrentDebugTypes(const char **Types, unsigned Count) {
+  assert(AppendedDebugTypeSizes->size() == 0 &&
+         "Resetting CurrentDebugType when it was previously appended to");
   CurrentDebugType->clear();
   llvm::append_range(*CurrentDebugType, ArrayRef(Types, Count));
 }
diff --git a/llvm/unittests/Support/DebugTest.cpp b/llvm/unittests/Support/DebugTest.cpp
index e8b7548..3874142 100644
--- a/llvm/unittests/Support/DebugTest.cpp
+++ b/llvm/unittests/Support/DebugTest.cpp
@@ -19,8 +19,8 @@ using namespace llvm;
 TEST(DebugTest, Basic) {
   std::string s1, s2;
   raw_string_ostream os1(s1), os2(s2);
-  static const char *DT[] = {"A", "B"};  
-  
+  static const char *DT[] = {"A", "B"};
+
   llvm::DebugFlag = true;
   setCurrentDebugTypes(DT, 2);
   DEBUG_WITH_TYPE("A", os1 << "A");
@@ -50,4 +50,25 @@ TEST(DebugTest, CommaInDebugBlock) {
   });
   EXPECT_EQ("ZYX", os1.str());
 }
+
+TEST(DebugTest, AppendAndPop) {
+  std::string s1, s2, s3;
+  raw_string_ostream os1(s1), os2(s2), os3(s3);
+
+  llvm::DebugFlag = true;
+  appendDebugType("A");
+  DEBUG_WITH_TYPE("A", os1 << "A");
+  DEBUG_WITH_TYPE("B", os1 << "B");
+  EXPECT_EQ("A", os1.str());
+
+  appendDebugType("B");
+  DEBUG_WITH_TYPE("A", os2 << "A");
+  DEBUG_WITH_TYPE("B", os2 << "B");
+  EXPECT_EQ("AB", os2.str());
+
+  popAppendedDebugTypes();
+  DEBUG_WITH_TYPE("A", os3 << "A");
+  DEBUG_WITH_TYPE("B", os3 << "B");
+  EXPECT_EQ("A", os3.str());
+}
 #endif