Ensure that GenerateStoreFastDoubleElement returns stored value on all paths.

src/arm/stub-cache-arm.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4381 matching lines @@
   __ add(scratch, scratch,
          Operand(key_reg, LSL, kDoubleSizeLog2 - kSmiTagSize));
   // scratch is now effective address of the double element
 
   FloatingPointHelper::Destination destination;
   if (CpuFeatures::IsSupported(VFP3)) {
     destination = FloatingPointHelper::kVFPRegisters;
   } else {
     destination = FloatingPointHelper::kCoreRegisters;
   }
-  __ SmiUntag(value_reg, value_reg);
+
+  Register untagged_value = receiver_reg;
+  __ SmiUntag(untagged_value, value_reg);
   FloatingPointHelper::ConvertIntToDouble(
-      masm, value_reg, destination,
-      d0, mantissa_reg, exponent_reg,  // These are: double_dst, dst1, dst2.
-      scratch4, s2);  // These are: scratch2, single_scratch.
+      masm,
+      untagged_value,
+      destination,
+      d0,
+      mantissa_reg,
+      exponent_reg,
+      scratch4,
+      s2);
   if (destination == FloatingPointHelper::kVFPRegisters) {
     CpuFeatures::Scope scope(VFP3);
     __ vstr(d0, scratch, 0);
   } else {
     __ str(mantissa_reg, MemOperand(scratch, 0));
     __ str(exponent_reg, MemOperand(scratch, Register::kSizeInBytes));
   }
   __ Ret();
 
   // Handle store cache miss, replacing the ic with the generic stub.
   __ bind(&miss_force_generic);
   Handle<Code> ic =
       masm->isolate()->builtins()->KeyedStoreIC_MissForceGeneric();
   __ Jump(ic, RelocInfo::CODE_TARGET);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM