Porting r9392 to arm (smi-only arrays).

src/arm/ic-arm.cc

Index: src/arm/ic-arm.cc
diff --git a/src/arm/ic-arm.cc b/src/arm/ic-arm.cc
index 145d668d76c83238d98f8f173ad965c9d5686588..9932125a719baedf5b1712fb22bf8e2e4099cbc2 100644
--- a/src/arm/ic-arm.cc
+++ b/src/arm/ic-arm.cc
@@ -1360,6 +1360,20 @@ void KeyedStoreIC::GenerateGeneric(MacroAssembler* masm,
   __ bind(&fast);
   Register scratch_value = r4;
   Register address = r5;
+  if (FLAG_smi_only_arrays) {
+    Label not_smi_only;
+    // Make sure the elements are smi-only.
+    __ ldr(scratch_value, FieldMemOperand(receiver, HeapObject::kMapOffset));
+    __ CheckFastSmiOnlyElements(scratch_value, scratch_value, &not_smi_only);
+    // Non-smis need to call into the runtime if the array is smi only.
+    __ JumpIfNotSmi(value, &slow);
+    __ add(address, elements,
+           Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+    __ add(address, address, Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));
+    __ str(value, MemOperand(address));
+    __ Ret();
+    __ bind(&not_smi_only);
+  }
   // Fast case, store the value to the elements backing store.
   __ add(address, elements, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
   __ add(address, address, Operand(key, LSL, kPointerSizeLog2 - kSmiTagSize));