Index: include/clang/Driver/Multilib.h
===================================================================
--- include/clang/Driver/Multilib.h
+++ include/clang/Driver/Multilib.h
@@ -97,6 +97,10 @@
   typedef multilib_list::iterator iterator;
   typedef multilib_list::const_iterator const_iterator;
 
+  typedef std::function<std::vector<std::string>(
+      StringRef InstallDir, StringRef Triple, const Multilib &M)>
+  IncludeDirsFunc;
+
   struct FilterCallback {
     virtual ~FilterCallback() {};
     /// \return true iff the filter should remove the Multilib from the set
@@ -105,6 +109,7 @@
 
 private:
   multilib_list Multilibs;
+  IncludeDirsFunc IncludeCallback;
 
 public:
   MultilibSet() {}
@@ -150,6 +155,12 @@
 
   void print(raw_ostream &OS) const;
 
+  MultilibSet &includeDirsCallback(IncludeDirsFunc F) {
+    IncludeCallback = F;
+    return *this;
+  }
+  IncludeDirsFunc includeDirsCallback() const { return IncludeCallback; }
+
 private:
   /// Apply the filter to Multilibs and return the subset that remains
   static multilib_list filterCopy(const FilterCallback &F,
Index: lib/Driver/ToolChains.cpp
===================================================================
--- lib/Driver/ToolChains.cpp
+++ lib/Driver/ToolChains.cpp
@@ -1726,7 +1726,14 @@
       .Maybe(SoftFloat)
       .Maybe(Nan2008)
       .FilterOut(".*sof/nan2008")
-      .FilterOut(NonExistent);
+      .FilterOut(NonExistent)
+      .includeDirsCallback([](
+          StringRef InstallDir, StringRef TripleStr, const Multilib &M) {
+        std::vector<std::string> Dirs;
+        Dirs.push_back((InstallDir + "/include").str());
+        Dirs.push_back((InstallDir + "/../../../../sysroot/usr/include").str());
+        return Dirs;
+      });
   }
 
   // Check for Code Sourcery toolchain multilibs
@@ -1771,7 +1778,15 @@
       .Maybe(MAbi64)
       .FilterOut("/mips16.*/64")
       .FilterOut("/micromips.*/64")
-      .FilterOut(NonExistent);
+      .FilterOut(NonExistent)
+      .includeDirsCallback([](
+          StringRef InstallDir, StringRef TripleStr, const Multilib &M) {
+        std::vector<std::string> Dirs;
+        Dirs.push_back((InstallDir + "/include").str());
+        Dirs.push_back((InstallDir + "/../../../../" + TripleStr +
+                        "/libc/usr/include").str());
+        return Dirs;
+      });
   }
 
   MultilibSet AndroidMipsMultilibs = MultilibSet()
@@ -1813,7 +1828,14 @@
       .Maybe(Mips64r6)
       .Maybe(MAbi64)
       .Maybe(LittleEndian)
-      .FilterOut(NonExistent);
+      .FilterOut(NonExistent)
+      .includeDirsCallback([](
+          StringRef InstallDir, StringRef TripleStr, const Multilib &M) {
+        std::vector<std::string> Dirs;
+        Dirs.push_back((InstallDir + "/include").str());
+        Dirs.push_back((InstallDir + "/../../../../sysroot/usr/include").str());
+        return Dirs;
+      });
   }
 
   StringRef CPUName;
@@ -3215,20 +3237,16 @@
   // Lacking those, try to detect the correct set of system includes for the
   // target triple.
 
-  // Sourcery CodeBench and modern FSF Mips toolchains put extern C
-  // system includes under three additional directories.
-  if (GCCInstallation.isValid() && isMipsArch(getTriple().getArch())) {
-    addExternCSystemIncludeIfExists(
-        DriverArgs, CC1Args, GCCInstallation.getInstallPath() + "/include");
-
-    addExternCSystemIncludeIfExists(
-        DriverArgs, CC1Args,
-        GCCInstallation.getInstallPath() + "/../../../../" +
-            GCCInstallation.getTriple().str() + "/libc/usr/include");
-
-    addExternCSystemIncludeIfExists(
-        DriverArgs, CC1Args,
-        GCCInstallation.getInstallPath() + "/../../../../sysroot/usr/include");
+  // Add include directories specific to the selected multilib set and multilib.
+  if (GCCInstallation.isValid()) {
+    auto Callback = Multilibs.includeDirsCallback();
+    if (Callback) {
+      const auto IncludePaths = Callback(GCCInstallation.getInstallPath(),
+                                         GCCInstallation.getTriple().str(),
+                                         GCCInstallation.getMultilib());
+      for (const auto &Path : IncludePaths)
+        addExternCSystemIncludeIfExists(DriverArgs, CC1Args, Path);
+    }
   }
 
   // Implement generic Debian multiarch support.