Merge pull request #2502 from kugelfuhr/kugelfuhr/fix-2461

Fix issue #2461

src/cc65/codeoptutil.c

@@ -1128,8 +1128,10 @@ void AddOpHigh (StackOpData* D, opc_t OPC, LoadInfo* LI, int KeepResult)
             InsertEntry (D, X, D->IP++);
         }
 
-        /* In both cases, we can remove the load */
+        /* If this is the right hand side, we can remove the load. */
+        if (LI == &D->Rhs) {
             LI->X.Flags |= LI_REMOVE;
+        }
 
     } else {
         /* opc zphi */

test/val/bug2461.c

@@ -0,0 +1,67 @@
+/* related to bug #2461 */
+
+/* Note: The values for MASK1, MASK2, the return values of GarbleAX and the 
+ * arguments for CALC() are carefully chosen to elicit the bug.
+ */
+
+#include <stdio.h>
+
+#define MASK1           0x000FU
+#define MASK2           0x00FFU
+#define CALC(num, op)   (((num) & (~MASK1)) op ((num) & MASK2))
+
+static unsigned Failures = 0;
+static unsigned TestCount = 0;
+
+unsigned GarbleAX(void)
+{
+    static const unsigned Garbage[] = {
+        0x1234, 0x0000, 0x1234, 0x1234
+    };
+    return Garbage[TestCount - 1];
+}
+
+unsigned WrongAdd(unsigned num)
+{
+    unsigned ret=GarbleAX();
+    return CALC(num, +);
+}
+
+unsigned WrongAnd(unsigned num)
+{
+    unsigned ret=GarbleAX();
+    return CALC(num, &);
+}
+
+unsigned WrongOr(unsigned num)
+{
+    unsigned ret=GarbleAX();
+    return CALC(num, |);
+}
+
+unsigned WrongXor(unsigned num)
+{
+    unsigned ret=GarbleAX();
+    return CALC(num, ^);
+}
+
+void Test(unsigned (*F)(unsigned), unsigned Num, unsigned Ref)
+{
+    unsigned Res;
+    ++TestCount;
+    Res = F(Num);
+    if (Res != Ref) {
+        printf("Test %u failed: got %04X, expected %04X\n", TestCount, Res, Ref);
+        ++Failures;
+    }
+}
+
+int main(void)
+{
+    Test(WrongAdd, 0x4715, CALC(0x4715, +));
+    Test(WrongAnd, 0x4715, CALC(0x4715, &));
+    Test(WrongOr,  0x4715, CALC(0x4715, |));
+    Test(WrongXor, 0x4715, CALC(0x4715, ^));
+    printf("Failures: %u\n", Failures);
+    return Failures;
+}