(Cheaper) overflow check for const rhs.

Cython/Compiler/ExprNodes.py

@@ -8013,7 +8013,10 @@ class NumBinopNode(BinopNode):
             self.infix = False
         if self.type.is_int and env.directives['overflowcheck'] and self.operator in ('+', '-', '*'):
             self.overflow_check = True
-            self.func = self.type.overflow_check_binop(self.op_names[self.operator], env)
+            self.func = self.type.overflow_check_binop(
+                self.op_names[self.operator],
+                env,
+                const_rhs = self.operand2.has_constant_result())
             self.is_temp = True
         if not self.infix or (type1.is_numeric and type2.is_numeric):
             self.operand1 = self.operand1.coerce_to(self.type, env)

Cython/Compiler/PyrexTypes.py

@@ -402,7 +402,9 @@ class CTypedefType(BaseType):
         # delegation
         return self.typedef_base_type.create_from_py_utility_code(env)
 
-    def overflow_check_binop(self, binop, env):
+    def overflow_check_binop(self, binop, env, const_rhs=False):
+        if const_rhs:
+            binop += "_const"
         env.use_utility_code(UtilityCode.load("Common", "Overflow.c"))
         type = self.declaration_code("")
         name = self.specialization_name()
@@ -1557,10 +1559,12 @@ class CIntType(CNumericType):
             # be negative for signed ints, which is good.
             return "0xbad0bad0"
 
-    def overflow_check_binop(self, binop, env):
+    def overflow_check_binop(self, binop, env, const_rhs=False):
         env.use_utility_code(UtilityCode.load("Common", "Overflow.c"))
         type = self.declaration_code("")
         name = self.specialization_name()
+        if const_rhs:
+            binop += "_const"
         if type in ('int', 'long', 'long long'):
             env.use_utility_code(TempitaUtilityCode.load("BaseCaseSigned", "Overflow.c", context={'INT': type, 'NAME': name}))
         elif type in ('unsigned int', 'unsigned long', 'unsigned long long'):