Change: Optimise trivial right shift operations on variables

OpenTTD · Apr 3, 2023 · 1e26f14 · 1e26f14
1 parent 30842d3
commit 1e26f14
Show file tree

Hide file tree

Showing 3 changed files with 20 additions and 4 deletions.
diff --git a/nml/expression/binop.py b/nml/expression/binop.py
@@ -186,6 +186,24 @@ def reduce(self, id_dicts=None, unknown_id_fatal=True):
                 expr1.mask = nmlop.SHIFT_LEFT(expr1.mask, expr2).reduce()
                 return expr1
 
+            if (
+                (
+                    op == nmlop.SHIFTU_RIGHT
+                    or (
+                        op == nmlop.SHIFT_RIGHT
+                        and isinstance(expr1.mask, ConstantNumeric)
+                        and expr1.mask.uvalue < 0x80000000
+                    )
+                )
+                and isinstance(expr2, ConstantNumeric)
+                and expr2.value >= 0
+                and expr1.shift.value >= 0
+                and (expr1.shift.value + expr2.value) < 32
+            ):
+                expr1.shift.value += expr2.value
+                expr1.mask = nmlop.SHIFTU_RIGHT(expr1.mask, expr2).reduce()
+                return expr1
+
         # - Try to merge multiple additions/subtractions with constant numbers
         if (
             op in (nmlop.ADD, nmlop.SUB)

diff --git a/regression/expected/example_train.grf b/regression/expected/example_train.grf
diff --git a/regression/expected/example_train.nfo b/regression/expected/example_train.nfo
@@ -505,10 +505,8 @@ FF \wx00FD 	// @action3_4;
 \wx00FD // default: set_cargo_wagon_load;
 
 // Name: cargo_wagon_switch_graphics
-117 * 37 02 00 FD 89
-10 20 \dxFFFFFFFF
-\2u>> 1A 20 \dx00000008
-\2& 1A 00 \dx000000FF
+117 * 23 02 00 FD 89
+10 08 \dx000000FF
 \b1
 \wx00F1 \dx00000000 \dx00000000 	// 0 .. 0: cargo_wagon_switch_vehicle;
 \wx00FD // default: cargo_wagon_switch_load;