diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index e99de130779..378235e1aaf 100644
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -264,6 +264,12 @@ public:
         hasConsumedDollar(false) {
     // Initialize the set of available features.
     setAvailableFeatures(ComputeAvailableFeatures(STI.getFeatureBits()));
+
+    // Assert exactly one ABI was chosen.
+    assert((((STI.getFeatureBits() & Mips::FeatureO32) != 0) +
+            ((STI.getFeatureBits() & Mips::FeatureEABI) != 0) +
+            ((STI.getFeatureBits() & Mips::FeatureN32) != 0) +
+            ((STI.getFeatureBits() & Mips::FeatureN64) != 0)) == 1);
   }
 
   MCAsmParser &getParser() const { return Parser; }
diff --git a/lib/Target/Mips/Mips.td b/lib/Target/Mips/Mips.td
index c7ebdac1c05..a9e8dca80b4 100644
--- a/lib/Target/Mips/Mips.td
+++ b/lib/Target/Mips/Mips.td
@@ -90,11 +90,11 @@ def FeatureMicroMips  : SubtargetFeature<"micromips", "InMicroMipsMode", "true",
 class Proc<string Name, list<SubtargetFeature> Features>
  : Processor<Name, MipsGenericItineraries, Features>;
 
-def : Proc<"mips32", [FeatureMips32]>;
-def : Proc<"mips32r2", [FeatureMips32r2]>;
-def : Proc<"mips64", [FeatureMips64]>;
-def : Proc<"mips64r2", [FeatureMips64r2]>;
-def : Proc<"mips16", [FeatureMips16]>;
+def : Proc<"mips32", [FeatureMips32, FeatureO32]>;
+def : Proc<"mips32r2", [FeatureMips32r2, FeatureO32]>;
+def : Proc<"mips64", [FeatureMips64, FeatureN64]>;
+def : Proc<"mips64r2", [FeatureMips64r2, FeatureN64]>;
+def : Proc<"mips16", [FeatureMips16, FeatureO32]>;
 
 def MipsAsmParser : AsmParser {
   let ShouldEmitMatchRegisterName = 0;
diff --git a/lib/Target/Mips/MipsSubtarget.cpp b/lib/Target/Mips/MipsSubtarget.cpp
index a5d910e3e5d..f16fb798286 100644
--- a/lib/Target/Mips/MipsSubtarget.cpp
+++ b/lib/Target/Mips/MipsSubtarget.cpp
@@ -109,9 +109,12 @@ MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &CPU,
   // Initialize scheduling itinerary for the specified CPU.
   InstrItins = getInstrItineraryForCPU(CPUName);
 
-  // Set MipsABI if it hasn't been set yet.
-  if (MipsABI == UnknownABI)
-    MipsABI = hasMips64() ? N64 : O32;
+  // Assert exactly one ABI was chosen.
+  assert(MipsABI != UnknownABI);
+  assert((((getFeatureBits() & Mips::FeatureO32) != 0) +
+          ((getFeatureBits() & Mips::FeatureEABI) != 0) +
+          ((getFeatureBits() & Mips::FeatureN32) != 0) +
+          ((getFeatureBits() & Mips::FeatureN64) != 0)) == 1);
 
   // Check if Architecture and ABI are compatible.
   assert(((!hasMips64() && (isABI_O32() || isABI_EABI())) ||
diff --git a/test/CodeGen/Mips/2009-11-16-CstPoolLoad.ll b/test/CodeGen/Mips/2009-11-16-CstPoolLoad.ll
index 2b2ee0fd7ad..c3791dfc7ce 100644
--- a/test/CodeGen/Mips/2009-11-16-CstPoolLoad.ll
+++ b/test/CodeGen/Mips/2009-11-16-CstPoolLoad.ll
@@ -1,9 +1,9 @@
 ; RUN: llc -march=mipsel -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-O32
 ; RUN: llc -march=mipsel -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-O32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
 
 define float @h() nounwind readnone {
 entry:
diff --git a/test/CodeGen/Mips/blockaddr.ll b/test/CodeGen/Mips/blockaddr.ll
index d0319cab2db..d6dc7e7b24b 100644
--- a/test/CodeGen/Mips/blockaddr.ll
+++ b/test/CodeGen/Mips/blockaddr.ll
@@ -1,9 +1,9 @@
 ; RUN: llc -march=mipsel -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-O32
 ; RUN: llc -march=mipsel -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-O32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
 ; RUN: llc -mtriple=mipsel-linux-gnu -march=mipsel -mcpu=mips32 -mattr=+mips16 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-MIPS16-1
 ; RUN: llc -mtriple=mipsel-linux-gnu -march=mipsel -mcpu=mips32 -mattr=+mips16 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-MIPS16-2
 
diff --git a/test/CodeGen/Mips/global-address.ll b/test/CodeGen/Mips/global-address.ll
index 0d49a7424ad..0785cfcc051 100644
--- a/test/CodeGen/Mips/global-address.ll
+++ b/test/CodeGen/Mips/global-address.ll
@@ -1,9 +1,9 @@
 ; RUN: llc -march=mipsel -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-O32
 ; RUN: llc -march=mipsel -relocation-model=static -mtriple=mipsel-linux-gnu < %s | FileCheck %s -check-prefix=STATIC-O32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n32 -relocation-model=static  -mtriple=mipsel-linux-gnu < %s | FileCheck %s -check-prefix=STATIC-N32
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
-; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n32 -relocation-model=static  -mtriple=mipsel-linux-gnu < %s | FileCheck %s -check-prefix=STATIC-N32
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=pic < %s | FileCheck %s -check-prefix=PIC-N64
+; RUN: llc -march=mips64el -mcpu=mips64r2 -mattr=-n64,n64 -relocation-model=static < %s | FileCheck %s -check-prefix=STATIC-N64
 
 @s1 = internal unnamed_addr global i32 8, align 4
 @g1 = external global i32
diff --git a/test/CodeGen/Mips/mips64fpldst.ll b/test/CodeGen/Mips/mips64fpldst.ll
index 24647b20bf2..368ab83514f 100644
--- a/test/CodeGen/Mips/mips64fpldst.ll
+++ b/test/CodeGen/Mips/mips64fpldst.ll
@@ -1,5 +1,5 @@
-; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=n64 | FileCheck %s -check-prefix=CHECK-N64
-; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=n32 | FileCheck %s -check-prefix=CHECK-N32
+; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=-n64,n64 | FileCheck %s -check-prefix=CHECK-N64
+; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=-n64,n32 | FileCheck %s -check-prefix=CHECK-N32
 
 @f0 = common global float 0.000000e+00, align 4
 @d0 = common global double 0.000000e+00, align 8
diff --git a/test/CodeGen/Mips/mips64intldst.ll b/test/CodeGen/Mips/mips64intldst.ll
index 0e310a8670f..62244f60b00 100644
--- a/test/CodeGen/Mips/mips64intldst.ll
+++ b/test/CodeGen/Mips/mips64intldst.ll
@@ -1,5 +1,5 @@
-; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=n64 | FileCheck %s -check-prefix=CHECK-N64
-; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=n32 | FileCheck %s -check-prefix=CHECK-N32
+; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=-n64,n64 | FileCheck %s -check-prefix=CHECK-N64
+; RUN: llc  < %s -march=mips64el -mcpu=mips64 -mattr=-n64,n32 | FileCheck %s -check-prefix=CHECK-N32
 
 @c = common global i8 0, align 4
 @s = common global i16 0, align 4
diff --git a/test/MC/Mips/elf_eflags.s b/test/MC/Mips/elf_eflags.s
index 7a497785d2d..5da72e514bc 100644
--- a/test/MC/Mips/elf_eflags.s
+++ b/test/MC/Mips/elf_eflags.s
@@ -13,10 +13,10 @@
 # RUN: llvm-mc -filetype=obj -triple mipsel-unknown-linux -mcpu=mips32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPSEL-MIPS32 %s
 # MIPSEL-MIPS32: Flags [ (0x50001000)
 
-# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64r2 -mattr=n32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64R2-N32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64r2 -mattr=-n64,n32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64R2-N32 %s
 # MIPS64EL-MIPS64R2-N32: Flags [ (0x80000020)
 
-# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64 -mattr=n32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64-N32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64 -mattr=-n64,n32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64-N32 %s
 # MIPS64EL-MIPS64-N32: Flags [ (0x60000020)
 
 # RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64r2 -mattr=n64 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64R2-N64 %s
@@ -25,10 +25,10 @@
 # RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64 %s -mattr=n64 -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64-N64 %s
 # MIPS64EL-MIPS64-N64: Flags [ (0x60000000)
 
-# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64r2 -mattr=o32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64R2-O32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64r2 -mattr=-n64,o32 %s -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64R2-O32 %s
 # MIPS64EL-MIPS64R2-O32: Flags [ (0x80001100)
 
-# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64 %s -mattr=o32 -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64-O32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64el-unknown-linux -mcpu=mips64 %s -mattr=-n64,o32 -o -| llvm-readobj -h | FileCheck --check-prefix=MIPS64EL-MIPS64-O32 %s
 # MIPS64EL-MIPS64-O32: Flags [ (0x60001100)
 	
 # Default ABI for MIPS64 is N64 as opposed to GCC/GAS (N32)
diff --git a/test/MC/Mips/elf_reginfo.s b/test/MC/Mips/elf_reginfo.s
index 142606458ec..5e9ddf84d04 100644
--- a/test/MC/Mips/elf_reginfo.s
+++ b/test/MC/Mips/elf_reginfo.s
@@ -1,9 +1,9 @@
 # These *MUST* match the output of gas compiled with the same triple and
 # corresponding options (-mabi=64 -> -mattr=+n64 for example).
 
-# RUN: llvm-mc -filetype=obj -triple=mips64el-linux -mattr=+n64 %s -o - \
+# RUN: llvm-mc -filetype=obj -triple=mips64el-linux -mattr=-n64,+n64 %s -o - \
 # RUN: | llvm-readobj -s | FileCheck --check-prefix=CHECK_64 %s
-# RUN: llvm-mc -filetype=obj -triple=mipsel %s -mattr=+n32 -o - \
+# RUN: llvm-mc -filetype=obj -triple=mipsel %s -mattr=-o32,+n32 -o - \
 # RUN: | llvm-readobj -s | FileCheck --check-prefix=CHECK_32 %s
 
 # Check for register information sections.
diff --git a/test/MC/Mips/nabi-regs.s b/test/MC/Mips/nabi-regs.s
index 1c192c0e189..d79df4e2846 100644
--- a/test/MC/Mips/nabi-regs.s
+++ b/test/MC/Mips/nabi-regs.s
@@ -7,10 +7,10 @@
 # RUN:   -mcpu=mips64r2 -arch=mips64 | FileCheck %s
 #
 # RUN: llvm-mc %s -triple=mipsel-unknown-linux -show-encoding \
-# RUN:   -mcpu=mips64r2 -arch=mips64 -mattr=+n32 | FileCheck %s
+# RUN:   -mcpu=mips64r2 -arch=mips64 -mattr=-n64,+n32 | FileCheck %s
 #
 # RUN: llvm-mc %s -triple=mipsel-unknown-linux -show-encoding \
-# RUN:   -mcpu=mips64r2 -arch=mips64 -mattr=+n64 | FileCheck %s
+# RUN:   -mcpu=mips64r2 -arch=mips64 -mattr=-n64,+n64 | FileCheck %s
 
     .text
 foo: