add some more arithmetic ops

vyper/lll/optimizer.py

@@ -95,21 +95,39 @@ def apply_general_optimizations(node: LLLnode) -> LLLnode:
         argz = []
         value = ceil32(t.value)
 
-    elif node.value == "add" and get_int_at(argz, 0) == 0:
-        value = argz[1].value
-        annotation = argz[1].annotation
-        argz = argz[1].args
+    # swap args in add and mul if one is a literal so
+    # some of these optimizations are easier to write
+    elif node.value in {"add", "mul"} and int_at(argz, 0):
+        argz = [argz[1], argz[0]]
+        if node.value == "add" and get_int_at(argz, 1) == 0:
+            value = argz[1].value
+            annotation = argz[1].annotation
+            argz = argz[1].args
+        elif node.value == "mul" and get_int_at(argz, 1) == 0:
+            value = 0
+            annotation = argz[1].annotation
+            argz = []
+        elif node.value == "mul" and get_int_at(argz, 1) == 1:
+            value = argz[1].value
+            annotation = argz[1].annotation
+            argz = argz[1].args
 
-    elif node.value == "add" and get_int_at(argz, 1) == 0:
+    elif node.value in {"div", "sdiv"} and get_int_at(argz, 1) == 1:
         value = argz[0].value
         annotation = argz[0].annotation
         argz = argz[0].args
 
+    elif node.value in {"div", "sdiv", "smod", "mod"} and get_int_at(argz, 1) == 0:
+        value = 0
+        annotation = argz[0].annotation
+        argz = argz[0].args
+
     # TODO: rules for
     #   - mul by 0, 1, -1, power of two
     #   - div/sdiv by 0, 1, -1, power of two
     #   - mod/smod by 0, 1
     #   - shl/shr/sar
+    #   - lt/gt/le/ge/ne
 
     elif (
         node.value in ("clamp", "uclamp")