Index: lib/Frontend/InitHeaderSearch.cpp
===================================================================
--- lib/Frontend/InitHeaderSearch.cpp
+++ lib/Frontend/InitHeaderSearch.cpp
@@ -216,6 +216,7 @@
     case llvm::Triple::Bitrig:
     case llvm::Triple::NaCl:
     case llvm::Triple::PS4:
+    case llvm::Triple::ELFIAMCU:
       break;
     case llvm::Triple::Win32:
       if (triple.getEnvironment() != llvm::Triple::Cygnus)
@@ -318,6 +319,7 @@
   case llvm::Triple::CloudABI:
   case llvm::Triple::RTEMS:
   case llvm::Triple::NaCl:
+  case llvm::Triple::ELFIAMCU:
     break;
   case llvm::Triple::PS4: {
     // <isysroot> gets prepended later in AddPath().
Index: test/Driver/elfiamcu-header-search.c
===================================================================
--- test/Driver/elfiamcu-header-search.c
+++ test/Driver/elfiamcu-header-search.c
@@ -0,0 +1,6 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clang -target i386-pc-elfiamcu -c -v %s 2>&1 | FileCheck %s
+// CHECK-NOT: /usr/include
+// CHECK-NOT: /usr/local/include
+