diff --git a/include/clang/Basic/Diagnostic.h b/include/clang/Basic/Diagnostic.h
index 9c0a02c..22e7fb3 100644
--- a/include/clang/Basic/Diagnostic.h
+++ b/include/clang/Basic/Diagnostic.h
@@ -252,6 +252,11 @@
            "Cannot map errors!");
     setDiagnosticMappingInternal(Diag, Map, true);
   }
+  
+  /// setDiagnosticGroupMapping - Change an entire diagnostic group (e.g.
+  /// "unknown-pragmas" to have the specified mapping.  This returns true and
+  /// ignores the request if "Group" was unknown, false otherwise.
+  bool setDiagnosticGroupMapping(const char *Group, diag::Mapping Map);
 
   bool hasErrorOccurred() const { return ErrorOccurred; }
   bool hasFatalErrorOccurred() const { return FatalErrorOccurred; }
diff --git a/lib/Basic/Diagnostic.cpp b/lib/Basic/Diagnostic.cpp
index bf11a13..9986fc5 100644
--- a/lib/Basic/Diagnostic.cpp
+++ b/lib/Basic/Diagnostic.cpp
@@ -344,6 +344,64 @@
   return Result;
 }
 
+struct WarningOption {
+  const char  *Name;
+  const short *Members;
+  const char  *SubGroups;
+};
+
+#define GET_DIAG_ARRAYS
+#include "clang/Basic/DiagnosticGroups.inc"
+#undef GET_DIAG_ARRAYS
+
+// Second the table of options, sorted by name for fast binary lookup.
+static const WarningOption OptionTable[] = {
+#define GET_DIAG_TABLE
+#include "clang/Basic/DiagnosticGroups.inc"
+#undef GET_DIAG_TABLE
+};
+static const size_t OptionTableSize =
+sizeof(OptionTable) / sizeof(OptionTable[0]);
+
+static bool WarningOptionCompare(const WarningOption &LHS,
+                                 const WarningOption &RHS) {
+  return strcmp(LHS.Name, RHS.Name) < 0;
+}
+
+static void MapGroupMembers(const WarningOption *Group, diag::Mapping Mapping,
+                            Diagnostic &Diags) {
+  // Option exists, poke all the members of its diagnostic set.
+  if (const short *Member = Group->Members) {
+    for (; *Member != -1; ++Member)
+      Diags.setDiagnosticMapping(*Member, Mapping);
+  }
+  
+  // Enable/disable all subgroups along with this one.
+  if (const char *SubGroups = Group->SubGroups) {
+    for (; *SubGroups != (char)-1; ++SubGroups)
+      MapGroupMembers(&OptionTable[(unsigned char)*SubGroups], Mapping, Diags);
+  }
+}
+
+/// setDiagnosticGroupMapping - Change an entire diagnostic group (e.g.
+/// "unknown-pragmas" to have the specified mapping.  This returns true and
+/// ignores the request if "Group" was unknown, false otherwise.
+bool Diagnostic::setDiagnosticGroupMapping(const char *Group,
+                                           diag::Mapping Map) {
+  
+  WarningOption Key = { Group, 0, 0 };
+  const WarningOption *Found =
+  std::lower_bound(OptionTable, OptionTable + OptionTableSize, Key,
+                   WarningOptionCompare);
+  if (Found == OptionTable + OptionTableSize ||
+      strcmp(Found->Name, Group) != 0)
+    return true;  // Option not found.
+  
+  MapGroupMembers(Found, Map, *this);
+  return false;
+}
+
+
 /// ProcessDiag - This is the method used to report a diagnostic that is
 /// finally fully formed.
 void Diagnostic::ProcessDiag() {
diff --git a/tools/clang-cc/Warnings.cpp b/tools/clang-cc/Warnings.cpp
index 1ae122d..c3a6b21 100644
--- a/tools/clang-cc/Warnings.cpp
+++ b/tools/clang-cc/Warnings.cpp
@@ -40,45 +40,6 @@
 static llvm::cl::opt<bool> OptPedanticErrors("pedantic-errors");
 static llvm::cl::opt<bool> OptNoWarnings("w");
 
-struct WarningOption {
-  const char  *Name;
-  const short *Members;
-  const char  *SubGroups;
-};
-
-#define GET_DIAG_ARRAYS
-#include "clang/Basic/DiagnosticGroups.inc"
-#undef GET_DIAG_ARRAYS
-
-// Second the table of options, sorted by name for fast binary lookup.
-static const WarningOption OptionTable[] = {
-#define GET_DIAG_TABLE
-#include "clang/Basic/DiagnosticGroups.inc"
-#undef GET_DIAG_TABLE
-};
-static const size_t OptionTableSize =
-  sizeof(OptionTable) / sizeof(OptionTable[0]);
-
-static bool WarningOptionCompare(const WarningOption &LHS,
-                                 const WarningOption &RHS) {
-  return strcmp(LHS.Name, RHS.Name) < 0;
-}
-
-static void MapGroupMembers(const WarningOption *Group, diag::Mapping Mapping,
-                            Diagnostic &Diags) {
-  // Option exists, poke all the members of its diagnostic set.
-  if (const short *Member = Group->Members) {
-    for (; *Member != -1; ++Member)
-      Diags.setDiagnosticMapping(*Member, Mapping);
-  }
-
-  // Enable/disable all subgroups along with this one.
-  if (const char *SubGroups = Group->SubGroups) {
-    for (; *SubGroups != (char)-1; ++SubGroups)
-      MapGroupMembers(&OptionTable[(unsigned char)*SubGroups], Mapping, Diags);
-  }
-}
-
 bool clang::ProcessWarningOptions(Diagnostic &Diags) {
   Diags.setSuppressSystemWarnings(true);  // Default to -Wno-system-headers
   Diags.setIgnoreAllWarnings(OptNoWarnings);
@@ -144,17 +105,8 @@
       OptStart = Specifier;
     }
     
-    WarningOption Key = { OptStart, 0, 0 };
-    const WarningOption *Found =
-      std::lower_bound(OptionTable, OptionTable + OptionTableSize, Key,
-                       WarningOptionCompare);
-    if (Found == OptionTable + OptionTableSize ||
-        strcmp(Found->Name, OptStart) != 0) {
+    if (Diags.setDiagnosticGroupMapping(OptStart, Mapping))
       fprintf(stderr, "warning: unknown warning option: -W%s\n", Opt.c_str());
-      continue;
-    }
-    
-    MapGroupMembers(Found, Mapping, Diags);
   }
   
   return false;