Index: test/Preprocessor/arm-target-features.c
===================================================================
--- test/Preprocessor/arm-target-features.c	(revision 192701)
+++ test/Preprocessor/arm-target-features.c	(working copy)
@@ -9,3 +9,105 @@
 // CHECK-V7: __ARM_ARCH 7
 // CHECK-V7: __ARM_ARCH_7A__ 1
 // CHECK-NOT-V7: __ARM_FEATURE_CRC32
+
+// Check that -mhwdiv works properly for armv8/thumbv8 (enabled by default).
+
+// RUN: %clang -target armv8 -x c -E -dM %s -o - | FileCheck --check-prefix=ARMV8 %s
+// ARMV8:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv8 -mthumb -x c -E -dM %s -o - | FileCheck --check-prefix=THUMBV8 %s
+// THUMBV8:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv8 -mhwdiv=none -x c -E -dM %s -o - | FileCheck --check-prefix=NONEHWDIV-ARMV8 %s
+// NONEHWDIV-ARMV8-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv8 -mthumb -mhwdiv=none -x c -E -dM %s -o - | FileCheck --check-prefix=NONEHWDIV-THUMBV8 %s
+// NONEHWDIV-THUMBV8-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv8 -mhwdiv=thumb -x c -E -dM %s -o - | FileCheck --check-prefix=THUMBHWDIV-ARMV8 %s
+// THUMBHWDIV-ARMV8-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv8 -mthumb -mhwdiv=arm -x c -E -dM %s -o - | FileCheck --check-prefix=ARMHWDIV-THUMBV8 %s
+// ARMHWDIV-THUMBV8-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+
+// Test that -mhwdiv has the right effect for a target CPU which has hwdiv enabled by default.
+// RUN: %clang -target armv7 -mcpu=cortex-a15 -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-ARM %s
+// DEFAULTHWDIV-ARM:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-a15 -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-THUMB %s
+// DEFAULTHWDIV-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target arm -mcpu=cortex-a15 -mhwdiv=thumb -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-THUMBHWDIV-ARM %s
+// DEFAULTHWDIV-THUMBHWDIV-ARM-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target arm -mthumb -mcpu=cortex-a15 -mhwdiv=arm -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-ARMHWDIV-THUMB %s
+// DEFAULTHWDIV-ARMHWDIV-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target arm -mcpu=cortex-a15 -mhwdiv=none -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-NONEHWDIV-ARM %s
+// DEFAULTHWDIV-NONEHWDIV-ARM-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target arm -mthumb -mcpu=cortex-a15 -mhwdiv=none -x c -E -dM %s -o - | FileCheck --check-prefix=DEFAULTHWDIV-NONEHWDIV-THUMB %s
+// DEFAULTHWDIV-NONEHWDIV-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// FIXME: add check for further predefines
+// Test whether predefines are as expected when targeting cortex-a5.
+// RUN: %clang -target armv7 -mcpu=cortex-a5 -x c -E -dM %s -o - | FileCheck --check-prefix=A5-ARM %s
+// A5-ARM-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-a5 -x c -E -dM %s -o - | FileCheck --check-prefix=A5-THUMB %s
+// A5-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// Test whether predefines are as expected when targeting cortex-a8.
+// RUN: %clang -target armv7 -mcpu=cortex-a8 -x c -E -dM %s -o - | FileCheck --check-prefix=A8-ARM %s
+// A8-ARM-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-a8 -x c -E -dM %s -o - | FileCheck --check-prefix=A8-THUMB %s
+// A8-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// Test whether predefines are as expected when targeting cortex-a9.
+// RUN: %clang -target armv7 -mcpu=cortex-a9 -x c -E -dM %s -o - | FileCheck --check-prefix=A9-ARM %s
+// A9-ARM-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-a9 -x c -E -dM %s -o - | FileCheck --check-prefix=A9-THUMB %s
+// A9-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// Test whether predefines are as expected when targeting cortex-a15.
+// RUN: %clang -target armv7 -mcpu=cortex-a15 -x c -E -dM %s -o - | FileCheck --check-prefix=A15-ARM %s
+// A15-ARM:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-a15 -x c -E -dM %s -o - | FileCheck --check-prefix=A15-THUMB %s
+// A15-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// Test whether predefines are as expected when targeting swift.
+// RUN: %clang -target armv7s -mcpu=swift -x c -E -dM %s -o - | FileCheck --check-prefix=SWIFT-ARM %s
+// SWIFT-ARM:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv7s -mthumb -mcpu=swift -x c -E -dM %s -o - | FileCheck --check-prefix=SWIFT-THUMB %s
+// SWIFT-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// Test whether predefines are as expected when targeting cortex-a53.
+// RUN: %clang -target armv8 -mcpu=cortex-a53 -x c -E -dM %s -o - | FileCheck --check-prefix=A53-ARM %s
+// A53-ARM:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv8 -mthumb -mcpu=cortex-a53 -x c -E -dM %s -o - | FileCheck --check-prefix=A53-THUMB %s
+// A53-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// Test whether predefines are as expected when targeting cortex-r5.
+// RUN: %clang -target armv7 -mcpu=cortex-r5 -x c -E -dM %s -o - | FileCheck --check-prefix=R5-ARM %s
+// R5-ARM:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-r5 -x c -E -dM %s -o - | FileCheck --check-prefix=R5-THUMB %s
+// R5-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// Test whether predefines are as expected when targeting cortex-m0.
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-m0 -x c -E -dM %s -o - | FileCheck --check-prefix=M0-THUMB %s
+// M0-THUMB-NOT:#define __ARM_ARCH_EXT_IDIV__
+
+// Test whether predefines are as expected when targeting cortex-m3.
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-m3 -x c -E -dM %s -o - | FileCheck --check-prefix=M3-THUMB %s
+// M3-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
+
+// Test whether predefines are as expected when targeting cortex-m4.
+// RUN: %clang -target armv7 -mthumb -mcpu=cortex-m4 -x c -E -dM %s -o - | FileCheck --check-prefix=M4-THUMB %s
+// M4-THUMB:#define __ARM_ARCH_EXT_IDIV__ 1
Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp	(revision 192701)
+++ lib/Basic/Targets.cpp	(working copy)
@@ -3710,16 +3717,28 @@
   }
 
   void getDefaultFeatures(llvm::StringMap<bool> &Features) const {
+    StringRef ArchName = getTriple().getArchName();
     if (CPU == "arm1136jf-s" || CPU == "arm1176jzf-s" || CPU == "mpcore")
       Features["vfp2"] = true;
     else if (CPU == "cortex-a8" || CPU == "cortex-a9" ||
              CPU == "cortex-a9-mp") {
       Features["vfp3"] = true;
       Features["neon"] = true;
-    } else if (CPU == "swift" || CPU == "cortex-a5" ||
-        CPU == "cortex-a7" || CPU == "cortex-a15") {
+    }
+    else if (CPU == "cortex-a5") {
       Features["vfp4"] = true;
       Features["neon"] = true;
+    } else if (CPU == "swift" || CPU == "cortex-a7" || CPU == "cortex-a15") {
+      Features["vfp4"] = true;
+      Features["neon"] = true;
+      Features["hwdiv"] = true;
+      Features["hwdiv-arm"] = true;
+    } else if (CPU == "cortex-r5" || CPU == "cortex-a53" || CPU == "cortex-a57" ||
+        CPU == "cortex-m3" || CPU == "cortex-m4" ||
+        //  Enable the hwdiv extension for all v8 AArch32 cores by default.
+        ArchName.startswith("armv8") || ArchName.startswith("thumbv8")) {
+      Features["hwdiv"] = true;
+      Features["hwdiv-arm"] = true;
     }
   }