Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -7124,10 +7124,11 @@
 /// uses features that we can't model on machineinstrs, we have SDISel do the
 /// allocation.  This produces generally horrible, but correct, code.
 ///
-///   OpInfo describes the operand.
+///   OpInfo describes the operand
+///   RefOpInfo describes the matching operand if any, the operand otherwise
 static void GetRegistersForValue(SelectionDAG &DAG, const TargetLowering &TLI,
-                                 const SDLoc &DL,
-                                 SDISelAsmOperandInfo &OpInfo) {
+                                 const SDLoc &DL, SDISelAsmOperandInfo &OpInfo,
+                                 SDISelAsmOperandInfo &RefOpInfo) {
   LLVMContext &Context = *DAG.getContext();
 
   MachineFunction &MF = DAG.getMachineFunction();
@@ -7137,8 +7138,8 @@
   // If this is a constraint for a single physreg, or a constraint for a
   // register class, find it.
   std::pair<unsigned, const TargetRegisterClass *> PhysReg =
-      TLI.getRegForInlineAsmConstraint(&TRI, OpInfo.ConstraintCode,
-                                       OpInfo.ConstraintVT);
+      TLI.getRegForInlineAsmConstraint(&TRI, RefOpInfo.ConstraintCode,
+                                       RefOpInfo.ConstraintVT);
 
   unsigned NumRegs = 1;
   if (OpInfo.ConstraintVT != MVT::Other) {
@@ -7180,6 +7181,11 @@
     NumRegs = TLI.getNumRegisters(Context, OpInfo.ConstraintVT);
   }
 
+  // No need to allocate a matching input constraint since the constraint it's
+  // matching to has already been allocated.
+  if (OpInfo.isMatchingInputConstraint())
+    return;
+
   MVT RegVT;
   EVT ValueVT = OpInfo.ConstraintVT;
 
@@ -7428,19 +7434,27 @@
 
     // If this constraint is for a specific register, allocate it before
     // anything else.
+    SDISelAsmOperandInfo &RefOpInfo =
+        OpInfo.isMatchingInputConstraint()
+            ? ConstraintOperands[OpInfo.getMatchedOperand()]
+            : ConstraintOperands[i];
     if (OpInfo.ConstraintType == TargetLowering::C_Register)
-      GetRegistersForValue(DAG, TLI, getCurSDLoc(), OpInfo);
+      GetRegistersForValue(DAG, TLI, getCurSDLoc(), OpInfo, RefOpInfo);
   }
 
   // Third pass - Loop over all of the operands, assigning virtual or physregs
   // to register class operands.
   for (unsigned i = 0, e = ConstraintOperands.size(); i != e; ++i) {
     SDISelAsmOperandInfo &OpInfo = ConstraintOperands[i];
+    SDISelAsmOperandInfo &RefOpInfo =
+        OpInfo.isMatchingInputConstraint()
+            ? ConstraintOperands[OpInfo.getMatchedOperand()]
+            : ConstraintOperands[i];
 
     // C_Register operands have already been allocated, Other/Memory don't need
     // to be.
-    if (OpInfo.ConstraintType == TargetLowering::C_RegisterClass)
-      GetRegistersForValue(DAG, TLI, getCurSDLoc(), OpInfo);
+    if (RefOpInfo.ConstraintType == TargetLowering::C_RegisterClass)
+      GetRegistersForValue(DAG, TLI, getCurSDLoc(), OpInfo, RefOpInfo);
   }
 
   // AsmNodeOperands - The operands for the ISD::INLINEASM node.
Index: test/CodeGen/ARM/pr34170.ll
===================================================================
--- test/CodeGen/ARM/pr34170.ll
+++ test/CodeGen/ARM/pr34170.ll
@@ -10,4 +10,13 @@
   ret double %1
 }
 
+; Check support for returning a double in GPR with matching double input
+define double @dbl_gpr_matching_in_op(double %d) nounwind {
+; CHECK-LABEL: dbl_gpr_matching_in_op
+; CHECK: mov r1, r0
+; CHECK: vmov d0, r0, r1
+  %1 = call double asm "mov ${0:R}, ${1:Q}", "=&r,0"(double %d)
+  ret double %1
+}
+
 attributes #0 = { nounwind "target-features"="+d16,+vfp2,+vfp3,-fp-only-sp" }