optimize w=msb(w) => w>>=8, w=lsb(w) ==> w&=$00ff

codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt

@@ -431,6 +431,28 @@ class StatementOptimizer(private val program: Program,
             }
         }
 
+        // word = msb(word) , word=lsb(word)
+        if(assignment.target.inferType(program).isWords) {
+            var fcall = assignment.value as? FunctionCallExpression
+            if (fcall == null)
+                fcall = (assignment.value as? TypecastExpression)?.expression as? FunctionCallExpression
+            if (fcall != null && (fcall.target.nameInSource == listOf("lsb") || fcall.target.nameInSource == listOf("msb"))) {
+                if (fcall.args.single() isSameAs assignment.target) {
+                    return if (fcall.target.nameInSource == listOf("lsb")) {
+                        // optimize word=lsb(word) ==>  word &= $00ff
+                        val and255 = BinaryExpression(fcall.args[0], "&", NumericLiteralValue(DataType.UWORD, 255.0, fcall.position), fcall.position)
+                        val newAssign = Assignment(assignment.target, and255, AssignmentOrigin.OPTIMIZER, fcall.position)
+                        listOf(IAstModification.ReplaceNode(assignment, newAssign, parent))
+                    } else {
+                        // optimize word=msb(word) ==>  word >>= 8
+                        val shift8 = BinaryExpression(fcall.args[0], ">>", NumericLiteralValue(DataType.UBYTE, 8.0, fcall.position), fcall.position)
+                        val newAssign = Assignment(assignment.target, shift8, AssignmentOrigin.OPTIMIZER, fcall.position)
+                        listOf(IAstModification.ReplaceNode(assignment, newAssign, parent))
+                    }
+                }
+            }
+        }
+
         return noModifications
     }
 

docs/source/todo.rst

@@ -3,8 +3,6 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
-- optimize  w=msb(w)  =>  w >>=8,  w=lsb(w) ==> w &= $00ff
-
 fix the value of ww being wrong (with optimizations enabled) in :
     sub start() {
         byte ub1 = -50
@@ -20,9 +18,6 @@ fix the value of ww being wrong (with optimizations enabled) in :
     }
 
 
-...
-
-
 Need help with
 ^^^^^^^^^^^^^^
 - c128 target: various machine specific things (free zp locations, how banking works, getting the floating point routines working, ...)

examples/test.p8

@@ -3,25 +3,25 @@
 
 main {
     sub start() {
-        uword @shared xx=$ea31
+        byte bb1 = -50
-        ;xx &= $00ff
+        byte bb2 = -51
-        ;xx = lsb(xx)
+
-        ;txt.print_uwhex(xx, true)
+        word ww = func(bb1, bb2)
-        ;xx = $ea31
+        txt.print_w(ww)
-        ;xx &= $ff00
+        txt.print(" <- must be -50\n")          ; TODO fix this with noopt (prints 0) !
-        ; xx = msb(xx)
+
-;        %asm {{
+        ubyte ub1 = 50
-;            nop
+        ubyte ub2 = 51
-;            nop
+        uword uw = funcu(ub1, ub2)
-;        }}
+        txt.print_uw(uw)
-        xx >>= 8
+        txt.print(" <- must be 50\n")            ; TODO fix this with noopt (prints 0) !
-        %asm {{
+    }
-           nop
+
-        }}
+    sub func(word x1, word y1) -> word {
-        xx <<= 8
+        return x1
-        %asm {{
+    }
-           nop
+
-        }}
+    sub funcu(uword x1, uword y1) -> uword {
-        txt.print_uwhex(xx, true)
+        return x1
     }
 }