Allow to disable all sanitizers with "-fno-sanitize=all" option.

Summary:
This patch adds "all" sanitizer group. A shortcut "-fno-sanitize=all"
can be used to disable all sanitizers for a given source file.

"-fsanitize=all" option makes no sense, and will produce an error.

This group can also be useful when we add "-fsanitize-recover=<list>"
options (patch in http://reviews.llvm.org/D6302), as it would allow
to conveniently enable/disable recovery for all specified sanitizers.

Test Plan: regression test suite

Reviewers: kcc, rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D6733

llvm-svn: 224596
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 2692d77..adffad2 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -427,15 +427,24 @@
   assert((A->getOption().matches(options::OPT_fsanitize_EQ) ||
           A->getOption().matches(options::OPT_fno_sanitize_EQ)) &&
          "Invalid argument in parseArgValues!");
-  unsigned Kind = 0;
+  unsigned Kinds = 0;
   for (unsigned I = 0, N = A->getNumValues(); I != N; ++I) {
-    if (unsigned K = parseValue(A->getValue(I)))
-      Kind |= K;
+    const char *Value = A->getValue(I);
+    unsigned Kind;
+    // Special case: don't accept -fsanitize=all.
+    if (A->getOption().matches(options::OPT_fsanitize_EQ) &&
+        0 == strcmp("all", Value))
+      Kind = 0;
+    else
+      Kind = parseValue(Value);
+
+    if (Kind)
+      Kinds |= Kind;
     else if (DiagnoseErrors)
       D.Diag(clang::diag::err_drv_unsupported_option_argument)
-        << A->getOption().getName() << A->getValue(I);
+          << A->getOption().getName() << Value;
   }
-  return Kind;
+  return Kinds;
 }
 
 std::string lastArgumentForMask(const Driver &D, const llvm::opt::ArgList &Args,