Fix shl

tools/cc.py

@@ -339,14 +339,12 @@ orOp = make_cpu_bin_op('or')
 XorOp = make_cpu_bin_op('xor')
 
 class ShlOp(BinOp):
-    scratch_need = 3
+    scratch_need = 2
     def synth(self, scratches):
-        sc0, sc1, sc2 = scratches
-        return [f'or {sc0}, {self.right}, {self.right}',
+        sc0, sc1 = scratches
+        return [f'set {sc1}, 1',
                 f'or {self.dest}, {self.left}, {self.left}',
-                f'set {sc1}, 1',
-                f'set {sc2}, 0',
-                f'cmp {sc0}, {sc2}',
+                f'sub {sc0}, {self.right}, {sc1}',
                 f'beq [pc, 6]',
                 f'add {self.dest}, {self.dest}, {self.dest}',
                 f'sub {sc0}, {sc0}, {sc1}',