Index: lib/Lex/Pragma.cpp
===================================================================
--- lib/Lex/Pragma.cpp
+++ lib/Lex/Pragma.cpp
@@ -1024,10 +1024,19 @@
       return;
     }
 
-    if (PP.getDiagnostics().setSeverityForGroup(
-            WarningName[1] == 'W' ? diag::Flavor::WarningOrError
-                                  : diag::Flavor::Remark,
-            WarningName.substr(2), SV, DiagLoc))
+    diag::Flavor Flavor = WarningName[1] == 'W' ? diag::Flavor::WarningOrError
+                                                : diag::Flavor::Remark;
+    StringRef Group = WarningName.substr(2);
+    bool unknownDiag = false;
+    if (Group == "everything") {
+      // Special handling for pragma clang diagnostic ... "-Weverything"
+      // There is no formal group named "everything", so there has to be a
+      // special case for it.
+      PP.getDiagnostics().setSeverityForAll(Flavor, SV, DiagLoc);
+    } else
+      unknownDiag = PP.getDiagnostics().setSeverityForGroup(Flavor, Group, SV,
+                                                            DiagLoc);
+    if (unknownDiag)
       PP.Diag(StringLoc, diag::warn_pragma_diagnostic_unknown_warning)
         << WarningName;
     else if (Callbacks)
Index: test/Preprocessor/pragma_diagnostic.c
===================================================================
--- test/Preprocessor/pragma_diagnostic.c
+++ test/Preprocessor/pragma_diagnostic.c
@@ -30,3 +30,18 @@
 
 #pragma GCC diagnostic error "-Winvalid-name"  // expected-warning {{unknown warning group '-Winvalid-name', ignored}}
 
+
+// Testing pragma clang diagnostic with -Weverything
+void ppo(){} // First test that we do not diagnose on this.
+
+#pragma clang diagnostic warning "-Weverything"
+void ppp(){} // expected-warning {{no previous prototype for function 'ppp'}}
+
+#pragma clang diagnostic ignored "-Weverything" // Reset it.
+void ppq(){}
+
+#pragma clang diagnostic error "-Weverything" // Now set to error
+void ppr(){} // expected-error {{no previous prototype for function 'ppr'}}
+
+#pragma clang diagnostic warning "-Weverything" // This should not be effective
+void pps(){} // expected-error {{no previous prototype for function 'pps'}}
Index: test/Preprocessor/pushable-diagnostics.c
===================================================================
--- test/Preprocessor/pushable-diagnostics.c
+++ test/Preprocessor/pushable-diagnostics.c
@@ -15,3 +15,27 @@
 int c = 'df';  // expected-warning{{multi-character character constant}}
 
 #pragma clang diagnostic pop // expected-warning{{pragma diagnostic pop could not pop, no matching push}}
+
+// Test -Weverything
+
+void ppo0(){} // first verify that we do not give anything on this
+#pragma clang diagnostic push // now push
+
+#pragma clang diagnostic warning "-Weverything" 
+void ppr1(){} // expected-warning {{no previous prototype for function 'ppr1'}}
+
+#pragma clang diagnostic push // push again
+#pragma clang diagnostic ignored "-Weverything"  // Set to ignore in this level.
+void pps2(){}
+#pragma clang diagnostic warning "-Weverything"  // Set to warning in this level.
+void ppt2(){} // expected-warning {{no previous prototype for function 'ppt2'}}
+#pragma clang diagnostic error "-Weverything"  // Set to error in this level.
+void ppt3(){} // expected-error {{no previous prototype for function 'ppt3'}}
+#pragma clang diagnostic pop // pop should go back to warning level
+
+void pps1(){} // expected-warning {{no previous prototype for function 'pps1'}}
+
+
+#pragma clang diagnostic pop // Another pop should disble it again
+void ppu(){}
+