diff --git a/clang/include/clang/Driver/Multilib.h b/clang/include/clang/Driver/Multilib.h
--- a/clang/include/clang/Driver/Multilib.h
+++ b/clang/include/clang/Driver/Multilib.h
@@ -58,7 +58,7 @@
   const std::string &includeSuffix() const { return IncludeSuffix; }
 
   /// Get the flags that indicate or contraindicate this multilib's use
-  /// All elements begin with either '+' or '-'
+  /// All elements begin with either '-' or '!'
   const flags_list &flags() const { return Flags; }
 
   LLVM_DUMP_METHOD void dump() const;
diff --git a/clang/include/clang/Driver/MultilibBuilder.h b/clang/include/clang/Driver/MultilibBuilder.h
--- a/clang/include/clang/Driver/MultilibBuilder.h
+++ b/clang/include/clang/Driver/MultilibBuilder.h
@@ -70,7 +70,7 @@
   MultilibBuilder &includeSuffix(StringRef S);
 
   /// Get the flags that indicate or contraindicate this multilib's use
-  /// All elements begin with either '+' or '-'
+  /// All elements begin with either '-' or '!'
   const flags_list &flags() const { return Flags; }
   flags_list &flags() { return Flags; }
 
diff --git a/clang/lib/Driver/Multilib.cpp b/clang/lib/Driver/Multilib.cpp
--- a/clang/lib/Driver/Multilib.cpp
+++ b/clang/lib/Driver/Multilib.cpp
@@ -49,7 +49,7 @@
   }
   OS << ";";
   for (StringRef Flag : Flags) {
-    if (Flag.front() == '+')
+    if (Flag.front() == '-')
       OS << "@" << Flag.substr(1);
   }
 }
diff --git a/clang/lib/Driver/MultilibBuilder.cpp b/clang/lib/Driver/MultilibBuilder.cpp
--- a/clang/lib/Driver/MultilibBuilder.cpp
+++ b/clang/lib/Driver/MultilibBuilder.cpp
@@ -76,7 +76,7 @@
     StringRef Flag(Flags[I]);
     llvm::StringMap<int>::iterator SI = FlagSet.find(Flag.substr(1));
 
-    assert(StringRef(Flag).front() == '+' || StringRef(Flag).front() == '-');
+    assert(StringRef(Flag).front() == '-' || StringRef(Flag).front() == '!');
 
     if (SI == FlagSet.end())
       FlagSet[Flag.substr(1)] = I;
@@ -97,10 +97,10 @@
 
 MultilibSetBuilder &MultilibSetBuilder::Maybe(const MultilibBuilder &M) {
   MultilibBuilder Opposite;
-  // Negate any '+' flags
+  // Negate positive flags
   for (StringRef Flag : M.flags()) {
-    if (Flag.front() == '+')
-      Opposite.flags().push_back(("-" + Flag.substr(1)).str());
+    if (Flag.front() == '-')
+      Opposite.flags().push_back(("!" + Flag.substr(1)).str());
   }
   return Either(M, Opposite);
 }
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -1921,9 +1921,9 @@
                             Multilib::flags_list &Flags) {
   assert(Flag.front() == '-');
   if (Enabled) {
-    Flags.push_back(("+" + Flag.substr(1)).str());
-  } else {
     Flags.push_back(Flag.str());
+  } else {
+    Flags.push_back(("!" + Flag.substr(1)).str());
   }
 }
 
diff --git a/clang/lib/Driver/ToolChains/OHOS.cpp b/clang/lib/Driver/ToolChains/OHOS.cpp
--- a/clang/lib/Driver/ToolChains/OHOS.cpp
+++ b/clang/lib/Driver/ToolChains/OHOS.cpp
@@ -40,15 +40,15 @@
   // -mfloat-abi=soft -mfloat-abi=softfp -mfloat-abi=hard
   // -mfpu=neon-vfpv4
   Multilibs.push_back(
-      Multilib("/a7_soft", {}, {}, {"+mcpu=cortex-a7", "+mfloat-abi=soft"}));
+      Multilib("/a7_soft", {}, {}, {"-mcpu=cortex-a7", "-mfloat-abi=soft"}));
 
   Multilibs.push_back(
       Multilib("/a7_softfp_neon-vfpv4", {}, {},
-               {"+mcpu=cortex-a7", "+mfloat-abi=softfp", "+mfpu=neon-vfpv4"}));
+               {"-mcpu=cortex-a7", "-mfloat-abi=softfp", "-mfpu=neon-vfpv4"}));
 
   Multilibs.push_back(
       Multilib("/a7_hard_neon-vfpv4", {}, {},
-               {"+mcpu=cortex-a7", "+mfloat-abi=hard", "+mfpu=neon-vfpv4"}));
+               {"-mcpu=cortex-a7", "-mfloat-abi=hard", "-mfpu=neon-vfpv4"}));
 
   if (Multilibs.select(Flags, Result.SelectedMultilib)) {
     Result.Multilibs = Multilibs;