diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 6e1c12d..9baef6b 100644
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -1107,6 +1107,7 @@
       RegSeq = SDValue(QuadDRegs(MVT::v4i64, V0, V1, V2, V3), 0);
     }
 
+    assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
     for (unsigned Vec = 0; Vec < NumVecs; ++Vec) {
       SDValue D = CurDAG->getTargetExtractSubreg(ARM::dsub_0+Vec,
                                                  dl, VT, RegSeq);
@@ -1187,6 +1188,7 @@
                                          V4, V5, V6, V7), 0);
 
       // Extract out the 3 / 4 Q registers.
+      assert(ARM::qsub_3 == ARM::qsub_0+3 && "Unexpected subreg numbering");
       for (unsigned Vec = 0; Vec < NumVecs; ++Vec) {
         SDValue Q = CurDAG->getTargetExtractSubreg(ARM::qsub_0+Vec,
                                                    dl, VT, RegSeq);
@@ -1345,6 +1347,7 @@
                                        V[4], V[5], V[6], V[7]), 0);
 
     // Store the even D registers.
+    assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
     Ops.push_back(Reg0); // post-access address offset
     for (unsigned Vec = 0; Vec < NumVecs; ++Vec)
       Ops.push_back(CurDAG->getTargetExtractSubreg(ARM::dsub_0+Vec*2, dl,
@@ -1570,6 +1573,8 @@
                                    V[4], V[5], V[6], V[7]), 0);
     }
 
+    assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+    assert(ARM::qsub_3 == ARM::qsub_0+3 && "Unexpected subreg numbering");
     unsigned SubIdx = is64BitVector ? ARM::dsub_0 : ARM::qsub_0;
     for (unsigned Vec = 0; Vec < NumVecs; ++Vec)
       ReplaceUses(SDValue(N, Vec),
diff --git a/lib/Target/ARM/ARMInstrNEON.td b/lib/Target/ARM/ARMInstrNEON.td
index e4dad65..197ec16 100644
--- a/lib/Target/ARM/ARMInstrNEON.td
+++ b/lib/Target/ARM/ARMInstrNEON.td
@@ -796,27 +796,32 @@
 //===----------------------------------------------------------------------===//
 
 // Extract D sub-registers of Q registers.
-// (dsub_0 is 5; dsub_1 is 6)
 def DSubReg_i8_reg  : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(5 + N->getZExtValue() / 8, MVT::i32);
+  assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::dsub_0 + N->getZExtValue()/8, MVT::i32);
 }]>;
 def DSubReg_i16_reg : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(5 + N->getZExtValue() / 4, MVT::i32);
+  assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::dsub_0 + N->getZExtValue()/4, MVT::i32);
 }]>;
 def DSubReg_i32_reg : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(5 + N->getZExtValue() / 2, MVT::i32);
+  assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::dsub_0 + N->getZExtValue()/2, MVT::i32);
 }]>;
 def DSubReg_f64_reg : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(5 + N->getZExtValue(), MVT::i32);
+  assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::dsub_0 + N->getZExtValue(), MVT::i32);
 }]>;
 def DSubReg_f64_other_reg : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(5 + (1 - N->getZExtValue()), MVT::i32);
+  assert(ARM::dsub_7 == ARM::dsub_0+7 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::dsub_0 + (1 - N->getZExtValue()),
+                                   MVT::i32);
 }]>;
 
 // Extract S sub-registers of Q/D registers.
-// (ssub_0 is 1; ssub_1 is 2; etc.)
 def SSubReg_f32_reg : SDNodeXForm<imm, [{
-  return CurDAG->getTargetConstant(1 + N->getZExtValue(), MVT::i32);
+  assert(ARM::ssub_3 == ARM::ssub_0+3 && "Unexpected subreg numbering");
+  return CurDAG->getTargetConstant(ARM::ssub_0 + N->getZExtValue(), MVT::i32);
 }]>;
 
 // Translate lane numbers from Q registers to D subregs.
diff --git a/lib/Target/ARM/ARMRegisterInfo.td b/lib/Target/ARM/ARMRegisterInfo.td
index 0c6c0e4..8dab8ca 100644
--- a/lib/Target/ARM/ARMRegisterInfo.td
+++ b/lib/Target/ARM/ARMRegisterInfo.td
@@ -446,6 +446,7 @@
 // sub registers for each register.
 //
 let Namespace = "ARM" in {
+// Note: Code depends on these having consecutive numbers.
 def ssub_0 : SubRegIndex { let NumberHack = 1; }
 def ssub_1 : SubRegIndex { let NumberHack = 2; }
 def ssub_2 : SubRegIndex { let NumberHack = 3; }