From 78263cd24b301406f9567f3e0a4fa03488445656 Mon Sep 17 00:00:00 2001
From: bbbradsmith <bbbradsmith@users.noreply.github.com>
Date: Fri, 17 Feb 2023 23:48:32 -0500
Subject: [PATCH] Fix OptStackOps label migration case for toscmpbool, add test
 case

---
 src/cc65/coptstop.c |  2 ++
 test/val/bug1989.c  | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 test/val/bug1989.c

diff --git a/src/cc65/coptstop.c b/src/cc65/coptstop.c
index 4d0151c55..8b2821dcd 100644
--- a/src/cc65/coptstop.c
+++ b/src/cc65/coptstop.c
@@ -1153,6 +1153,8 @@ static unsigned Opt_a_toscmpbool (StackOpData* D, const char* BoolTransformer)
 
         /* Save lhs into zeropage */
         AddStoreLhsA (D);
+        /* AddStoreLhsA may have moved the OpIndex, recalculate insertion point to prevent label migration. */
+        D->IP = D->OpIndex + 1;
 
         /* cmp */
         X = NewCodeEntry (OP65_CMP, AM65_ZP, D->ZPLo, 0, D->OpEntry->LI);
diff --git a/test/val/bug1989.c b/test/val/bug1989.c
new file mode 100644
index 000000000..b3e3d4c8d
--- /dev/null
+++ b/test/val/bug1989.c
@@ -0,0 +1,40 @@
+
+/* bug #1989 - OptStackOps Opt_a_toscmpbool bypassed a comparison, discovered in 544a49c */
+
+#include <stdlib.h>
+
+unsigned char i,r,j;
+
+void fail() // for the r=0 case, the == comparison was getting jumped over by OptStackOps
+{
+    if ((i & 0x1f) == (r ? 0 : 16)) j -=8;
+}
+
+void pass()
+{
+    if ((i & 0x1f) == (unsigned char)(r ? 0 : 16)) j -= 8;
+}
+
+void test(unsigned char ti, unsigned char tr, unsigned char tj)
+{
+    unsigned char rj;
+    i = ti;
+    r = tr;
+    j = tj;
+    pass();
+    rj = j;
+    i = ti;
+    r = tr;
+    j = tj;
+    fail();
+    if (j != rj) exit(1);
+}
+
+int main(void)
+{
+    test( 1,0,33);
+    test( 0,0,33);
+    test( 1,1,33);
+    test(16,1,33);
+    return 0;
+}