diff --git a/lib/Target/ARM/ARMSubtarget.cpp b/lib/Target/ARM/ARMSubtarget.cpp
index fa653759df4..199000f71f0 100644
--- a/lib/Target/ARM/ARMSubtarget.cpp
+++ b/lib/Target/ARM/ARMSubtarget.cpp
@@ -225,8 +225,8 @@ void ARMSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   // Insert the architecture feature derived from the target triple into the
   // feature string. This is important for setting features that are implied
   // based on the architecture version.
-  std::string ArchFS = ARM_MC::ParseARMTriple(TargetTriple.getTriple(),
-                                              CPUString);
+  std::string ArchFS =
+      ARM_MC::ParseARMTriple(TargetTriple.getTriple(), CPUString);
   if (!FS.empty()) {
     if (!ArchFS.empty())
       ArchFS = ArchFS + "," + FS.str();
@@ -246,29 +246,45 @@ void ARMSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   InstrItins = getInstrItineraryForCPU(CPUString);
 
   if (TargetABI == ARM_ABI_UNKNOWN) {
-    switch (TargetTriple.getEnvironment()) {
-    case Triple::Android:
-    case Triple::EABI:
-    case Triple::EABIHF:
-    case Triple::GNUEABI:
-    case Triple::GNUEABIHF:
-      TargetABI = ARM_ABI_AAPCS;
-      break;
-    default:
-      if (TargetTriple.isOSBinFormatMachO() &&
-          TargetTriple.getOS() == Triple::UnknownOS)
+    // FIXME: This is duplicated code from the front end and should be unified.
+    if (TargetTriple.isOSBinFormatMachO()) {
+      if (TargetTriple.getEnvironment() == llvm::Triple::EABI ||
+          (TargetTriple.getOS() == llvm::Triple::UnknownOS &&
+           TargetTriple.getObjectFormat() == llvm::Triple::MachO) ||
+          CPU.startswith("cortex-m")) {
         TargetABI = ARM_ABI_AAPCS;
-      else
+      } else {
         TargetABI = ARM_ABI_APCS;
-      break;
+      }
+    } else if (TargetTriple.isOSWindows()) {
+      // FIXME: this is invalid for WindowsCE
+      TargetABI = ARM_ABI_AAPCS;
+    } else {
+      // Select the default based on the platform.
+      switch (TargetTriple.getEnvironment()) {
+      case llvm::Triple::Android:
+      case llvm::Triple::GNUEABI:
+      case llvm::Triple::GNUEABIHF:
+      case llvm::Triple::EABIHF:
+      case llvm::Triple::EABI:
+        TargetABI = ARM_ABI_AAPCS;
+        break;
+      case llvm::Triple::GNU:
+	TargetABI = ARM_ABI_APCS;
+	break;
+      default:
+        if (TargetTriple.getOS() == llvm::Triple::NetBSD)
+          TargetABI = ARM_ABI_APCS;
+        else
+          TargetABI = ARM_ABI_AAPCS;
+        break;
+      }
     }
   }
 
   // FIXME: this is invalid for WindowsCE
-  if (isTargetWindows()) {
-    TargetABI = ARM_ABI_AAPCS;
+  if (isTargetWindows())
     NoARM = true;
-  }
 
   if (isAAPCS_ABI())
     stackAlignment = 8;
diff --git a/test/CodeGen/ARM/arm-abi-attr.ll b/test/CodeGen/ARM/arm-abi-attr.ll
index f3923ae5cc8..6219eb51541 100644
--- a/test/CodeGen/ARM/arm-abi-attr.ll
+++ b/test/CodeGen/ARM/arm-abi-attr.ll
@@ -1,5 +1,5 @@
-; RUN: llc -mtriple=arm-linux < %s | FileCheck %s --check-prefix=APCS
-; RUN: llc -mtriple=arm-linux -mattr=apcs < %s | \
+; RUN: llc -mtriple=arm-linux-gnu < %s | FileCheck %s --check-prefix=APCS
+; RUN: llc -mtriple=arm-linux-gnu -mattr=apcs < %s | \
 ; RUN: FileCheck %s --check-prefix=APCS
 ; RUN: llc -mtriple=arm-linux-gnueabi -mattr=apcs < %s | \
 ; RUN: FileCheck %s --check-prefix=APCS
diff --git a/test/CodeGen/ARM/atomic-64bit.ll b/test/CodeGen/ARM/atomic-64bit.ll
index 462c1859dc9..56e6ca4c390 100644
--- a/test/CodeGen/ARM/atomic-64bit.ll
+++ b/test/CodeGen/ARM/atomic-64bit.ll
@@ -1,6 +1,6 @@
 ; RUN: llc < %s -mtriple=armv7-apple-ios | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-LE
 ; RUN: llc < %s -mtriple=thumbv7-none-linux-gnueabihf | FileCheck %s --check-prefix=CHECK-THUMB --check-prefix=CHECK-THUMB-LE
-; RUN: llc < %s -mtriple=armebv7 | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-BE
+; RUN: llc < %s -mtriple=armebv7 -mattr=apcs | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-BE
 ; RUN: llc < %s -mtriple=thumbebv7-none-linux-gnueabihf | FileCheck %s --check-prefix=CHECK-THUMB --check-prefix=CHECK-THUMB-BE
 
 define i64 @test1(i64* %ptr, i64 %val) {
diff --git a/test/CodeGen/ARM/dagcombine-concatvector.ll b/test/CodeGen/ARM/dagcombine-concatvector.ll
index 62ed87fd787..a64630312a1 100644
--- a/test/CodeGen/ARM/dagcombine-concatvector.ll
+++ b/test/CodeGen/ARM/dagcombine-concatvector.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -mtriple=thumbv7s-apple-ios3.0.0 -mcpu=generic | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-LE
-; RUN: llc < %s -mtriple=thumbeb -mattr=v7,neon | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-BE
+; RUN: llc < %s -mtriple=thumbeb -mattr=apcs -mattr=v7,neon | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-BE
 
 ; PR15525
 ; CHECK-LABEL: test1:
diff --git a/test/CodeGen/ARM/emit-big-cst.ll b/test/CodeGen/ARM/emit-big-cst.ll
index 9a3367dab1a..c044355f2d6 100644
--- a/test/CodeGen/ARM/emit-big-cst.ll
+++ b/test/CodeGen/ARM/emit-big-cst.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=thumbv7-unknown-unknown < %s | FileCheck %s
+; RUN: llc -mtriple=thumbv7-unknown-unknown -mattr=apcs < %s | FileCheck %s
 ; Check assembly printing of odd constants.
 
 ; CHECK: bigCst:
diff --git a/test/CodeGen/ARM/tail-call.ll b/test/CodeGen/ARM/tail-call.ll
index c3e79652c03..8705c4245de 100644
--- a/test/CodeGen/ARM/tail-call.ll
+++ b/test/CodeGen/ARM/tail-call.ll
@@ -1,5 +1,6 @@
-; RUN: llc -mtriple armv7 -O0 -o - < %s | FileCheck %s -check-prefix CHECK-TAIL
-; RUN: llc -mtriple armv7 -O0 -disable-tail-calls -o - < %s \
+; RUN: llc -mtriple armv7 -mattr=apcs -O0 -o - < %s \
+; RUN:   | FileCheck %s -check-prefix CHECK-TAIL
+; RUN: llc -mtriple armv7 -mattr=apcs -O0 -disable-tail-calls -o - < %s \
 ; RUN:   | FileCheck %s -check-prefix CHECK-NO-TAIL
 
 declare i32 @callee(i32 %i)