[stubs] Split ToNumberStub into reusable subparts.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index 073ee7ea7d44bd6bc821fdc6bfb96b0c51055f51..abd517480f2c97bc87868a743a5549c44eb274f4 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -3046,6 +3046,17 @@ void MacroAssembler::JumpIfEitherSmi(Register reg1,
   b(eq, on_either_smi);
 }
 
+void MacroAssembler::AssertNotNumber(Register object) {
+  if (emit_debug_code()) {
+    STATIC_ASSERT(kSmiTag == 0);
+    tst(object, Operand(kSmiTagMask));
+    Check(ne, kOperandIsANumber);
+    push(object);
+    CompareObjectType(object, object, object, HEAP_NUMBER_TYPE);
+    pop(object);
+    Check(ne, kOperandIsANumber);
+  }
+}
 
 void MacroAssembler::AssertNotSmi(Register object) {
   if (emit_debug_code()) {