Index: include/llvm/Support/TargetParser.h
===================================================================
--- include/llvm/Support/TargetParser.h
+++ include/llvm/Support/TargetParser.h
@@ -17,6 +17,7 @@
 
 // FIXME: vector is used because that's what clang uses for subtarget feature
 // lists, but SmallVector would probably be better
+#include "llvm/ADT/Triple.h"
 #include <vector>
 
 namespace llvm {
@@ -140,6 +141,8 @@
 unsigned parseArchProfile(StringRef Arch);
 unsigned parseArchVersion(StringRef Arch);
 
+StringRef computeDefaultTargetABI(const Triple &TT, StringRef CPU);
+
 } // namespace ARM
 
 // FIXME:This should be made into class design,to avoid dupplication.
Index: lib/Support/TargetParser.cpp
===================================================================
--- lib/Support/TargetParser.cpp
+++ lib/Support/TargetParser.cpp
@@ -784,6 +784,44 @@
   return 0;
 }
 
+StringRef llvm::ARM::computeDefaultTargetABI(const Triple &TT, StringRef CPU) {
+  StringRef ArchName = CPU.empty() ?
+    TT.getArchName() :
+    ARM::getArchName(ARM::parseCPUArch(CPU));
+
+  if (TT.isOSBinFormatMachO()) {
+    if (TT.getEnvironment() == Triple::EABI ||
+        TT.getOS() == Triple::UnknownOS ||
+        llvm::ARM::parseArchProfile(ArchName) == ARM::PK_M)
+      return "aapcs";
+    if (TT.isWatchABI())
+      return "aapcs16";
+    return "apcs-gnu";
+  } else if (TT.isOSWindows())
+    // FIXME: this is invalid for WindowsCE.
+    return "aapcs";
+
+  // Select the default based on the platform.
+  switch (TT.getEnvironment()) {
+  case Triple::Android:
+  case Triple::GNUEABI:
+  case Triple::GNUEABIHF:
+  case Triple::MuslEABI:
+  case Triple::MuslEABIHF:
+    return "aapcs-linux";
+  case Triple::EABIHF:
+  case Triple::EABI:
+    return "aapcs";
+  default:
+    if (TT.isOSNetBSD())
+      return "apcs-gnu";
+    if (TT.isOSOpenBSD())
+      return "aapcs-linux";
+    return  "aapcs";
+  }
+}
+
+
 StringRef llvm::AArch64::getCanonicalArchName(StringRef Arch) {
   return ARM::getCanonicalArchName(Arch);
 }
Index: lib/Target/ARM/ARMTargetMachine.cpp
===================================================================
--- lib/Target/ARM/ARMTargetMachine.cpp
+++ lib/Target/ARM/ARMTargetMachine.cpp
@@ -109,60 +109,20 @@
 static ARMBaseTargetMachine::ARMABI
 computeTargetABI(const Triple &TT, StringRef CPU,
                  const TargetOptions &Options) {
-  if (Options.MCOptions.getABIName() == "aapcs16")
-    return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
-  else if (Options.MCOptions.getABIName().startswith("aapcs"))
-    return ARMBaseTargetMachine::ARM_ABI_AAPCS;
-  else if (Options.MCOptions.getABIName().startswith("apcs"))
-    return ARMBaseTargetMachine::ARM_ABI_APCS;
+  StringRef ABIName = Options.MCOptions.getABIName();
 
-  assert(Options.MCOptions.getABIName().empty() &&
-         "Unknown target-abi option!");
-
-  ARMBaseTargetMachine::ARMABI TargetABI =
-      ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
-
-  unsigned ArchKind = ARM::parseCPUArch(CPU);
-  StringRef ArchName = ARM::getArchName(ArchKind);
-  // FIXME: This is duplicated code from the front end and should be unified.
-  if (TT.isOSBinFormatMachO()) {
-    if (TT.getEnvironment() == Triple::EABI ||
-        (TT.getOS() == Triple::UnknownOS && TT.isOSBinFormatMachO()) ||
-        ARM::parseArchProfile(ArchName) == ARM::PK_M) {
-      TargetABI = ARMBaseTargetMachine::ARM_ABI_AAPCS;
-    } else if (TT.isWatchABI()) {
-      TargetABI = ARMBaseTargetMachine::ARM_ABI_AAPCS16;
-    } else {
-      TargetABI = ARMBaseTargetMachine::ARM_ABI_APCS;
-    }
-  } else if (TT.isOSWindows()) {
-    // FIXME: this is invalid for WindowsCE
-    TargetABI = ARMBaseTargetMachine::ARM_ABI_AAPCS;
-  } else {
-    // Select the default based on the platform.
-    switch (TT.getEnvironment()) {
-    case Triple::Android:
-    case Triple::GNUEABI:
-    case Triple::GNUEABIHF:
-    case Triple::MuslEABI:
-    case Triple::MuslEABIHF:
-    case Triple::EABIHF:
-    case Triple::EABI:
-      TargetABI = ARMBaseTargetMachine::ARM_ABI_AAPCS;
-      break;
-    case Triple::GNU:
-      TargetABI = ARMBaseTargetMachine::ARM_ABI_APCS;
-      break;
-    default:
-      if (TT.isOSNetBSD())
-        TargetABI = ARMBaseTargetMachine::ARM_ABI_APCS;
-      else
-        TargetABI = ARMBaseTargetMachine::ARM_ABI_AAPCS;
-      break;
-    }
+  if (!(ABIName.startswith("aapcs") || ABIName.startswith("apcs"))) {
+    assert(ABIName.empty() && "Unknown target-abi option!");
+    ABIName = ARM::computeDefaultTargetABI(TT, CPU);
   }
 
-  return TargetABI;
+  if (ABIName == "aapcs16")
+    return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
+  if (ABIName.startswith("aapcs"))
+    return ARMBaseTargetMachine::ARM_ABI_AAPCS;
+  if (ABIName.startswith("apcs"))
+    return ARMBaseTargetMachine::ARM_ABI_APCS;
+  return ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
 }
 
 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
Index: test/CodeGen/ARM/alloca.ll
===================================================================
--- test/CodeGen/ARM/alloca.ll
+++ test/CodeGen/ARM/alloca.ll
@@ -2,11 +2,11 @@
 
 define void @f(i32 %a) {
 entry:
-; CHECK: add  r11, sp, #4
+; CHECK: add  r11, sp, #8
         %tmp = alloca i8, i32 %a                ; <i8*> [#uses=1]
         call void @g( i8* %tmp, i32 %a, i32 1, i32 2, i32 3 )
         ret void
-; CHECK: sub  sp, r11, #4
+; CHECK: sub  sp, r11, #8
 }
 
 declare void @g(i8*, i32, i32, i32, i32)
Index: test/CodeGen/ARM/arm-abi-attr.ll
===================================================================
--- test/CodeGen/ARM/arm-abi-attr.ll
+++ test/CodeGen/ARM/arm-abi-attr.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=arm-linux-gnu < %s | FileCheck %s --check-prefix=APCS
+; RUN: llc -mtriple=arm-linux-gnu < %s | FileCheck %s --check-prefix=AAPCS
 ; RUN: llc -mtriple=arm-linux-gnu -target-abi=apcs < %s | \
 ; RUN: FileCheck %s --check-prefix=APCS
 ; RUN: llc -mtriple=arm-linux-gnueabi -target-abi=apcs < %s | \
Index: test/CodeGen/ARM/ctor_order.ll
===================================================================
--- test/CodeGen/ARM/ctor_order.ll
+++ test/CodeGen/ARM/ctor_order.ll
@@ -1,7 +1,7 @@
 ; RUN: llc < %s -mtriple=arm-apple-darwin  | FileCheck %s -check-prefix=DARWIN
 ; RUN: llc < %s -mtriple=arm-apple-darwin -relocation-model=dynamic-no-pic  | FileCheck %s --check-prefix=DARWIN
 ; RUN: llc < %s -mtriple=arm-apple-darwin -relocation-model=static  | FileCheck %s -check-prefix=DARWIN-STATIC
-; RUN: llc < %s -mtriple=arm-linux-gnu     | FileCheck %s -check-prefix=ELF
+; RUN: llc < %s -mtriple=arm-linux-gnu -target-abi=apcs  | FileCheck %s -check-prefix=ELF
 ; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s -check-prefix=GNUEABI
 
 ; DARWIN:      .section	__DATA,__mod_init_func,mod_init_funcs
Index: test/CodeGen/ARM/ctors_dtors.ll
===================================================================
--- test/CodeGen/ARM/ctors_dtors.ll
+++ test/CodeGen/ARM/ctors_dtors.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -mtriple=arm-apple-darwin  | FileCheck %s -check-prefix=DARWIN
-; RUN: llc < %s -mtriple=arm-linux-gnu     | FileCheck %s -check-prefix=ELF
+; RUN: llc < %s -mtriple=arm-linux-gnu -target-abi=apcs  | FileCheck %s -check-prefix=ELF
 ; RUN: llc < %s -mtriple=arm-linux-gnueabi | FileCheck %s -check-prefix=GNUEABI
 
 ; DARWIN: .section	__DATA,__mod_init_func,mod_init_funcs
Index: test/CodeGen/ARM/ssp-data-layout.ll
===================================================================
--- test/CodeGen/ARM/ssp-data-layout.ll
+++ test/CodeGen/ARM/ssp-data-layout.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -disable-fp-elim -march=arm -mcpu=cortex-a8 -mtriple arm-linux-gnu -o - | FileCheck %s
+; RUN: llc < %s -disable-fp-elim -march=arm -mcpu=cortex-a8 -mtriple arm-linux-gnu -target-abi=apcs -o - | FileCheck %s
 ;  This test is fairly fragile.  The goal is to ensure that "large" stack
 ;  objects are allocated closest to the stack protector (i.e., farthest away 
 ;  from the Stack Pointer.)  In standard SSP mode this means that large (>=
Index: test/CodeGen/ARM/str_pre-2.ll
===================================================================
--- test/CodeGen/ARM/str_pre-2.ll
+++ test/CodeGen/ARM/str_pre-2.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=armv6-linux-gnu | FileCheck %s
+; RUN: llc < %s -mtriple=armv6-linux-gnu -target-abi=apcs | FileCheck %s
 
 @b = external global i64*