From f45d2515eb9191f21bc21c8449e407ebfb3ee415 Mon Sep 17 00:00:00 2001
From: acqn <acqn163@outlook.com>
Date: Mon, 31 Aug 2020 01:56:57 +0800
Subject: [PATCH] Fixed OptPush1 in case later code would rely on that pushax
 zeroes register Y.

---
 src/cc65/coptpush.c | 19 +++++++++++++++++--
 src/cc65/coptpush.h |  6 +++---
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/cc65/coptpush.c b/src/cc65/coptpush.c
index 5c3daffca..34d794c64 100644
--- a/src/cc65/coptpush.c
+++ b/src/cc65/coptpush.c
@@ -56,12 +56,14 @@ unsigned OptPush1 (CodeSeg* S)
 **
 **     ldy     #xx+2
 **     jsr     pushwysp
+**     ldy     #$00     ; present if later code expects Y = 0
 **
-** saving 3 bytes and several cycles.
+** saving several cycles.
 */
 {
     unsigned I;
     unsigned Changes = 0;
+    unsigned R;
 
     /* Walk over the entries */
     I = 0;
@@ -79,7 +81,7 @@ unsigned OptPush1 (CodeSeg* S)
             (L[1] = CS_GetNextEntry (S, I)) != 0        &&
             !CE_HasLabel (L[1])                         &&
             CE_IsCallTo (L[1], "pushax")                &&
-            !RegAXUsed (S, I+2)) {
+            ((R = (GetRegInfo (S, I+2, REG_AXY))) & REG_AX) == 0) {
 
             /* Insert new code behind the pushax */
             const char* Arg;
@@ -94,12 +96,25 @@ unsigned OptPush1 (CodeSeg* S)
             X = NewCodeEntry (OP65_JSR, AM65_ABS, "pushwysp", 0, L[1]->LI);
             CS_InsertEntry (S, X, I+3);
 
+            /* pushax sets Y = 0 and following code might rely on this */
+            if ((R & REG_Y) != 0) {
+                /* ldy     #0 */
+                X = NewCodeEntry (OP65_LDY, AM65_IMM, MakeHexArg (0), 0, L[1]->LI);
+                CS_InsertEntry (S, X, I+4);
+            }
+
             /* Delete the old code */
             CS_DelEntries (S, I, 2);
 
             /* Remember, we had changes */
             ++Changes;
 
+            /* Skip the handled lines */
+            if ((R & REG_Y) == 0) {
+                ++I;
+            } else {
+                I += 2;
+            }
         }
 
         /* Next entry */
diff --git a/src/cc65/coptpush.h b/src/cc65/coptpush.h
index 0d637e824..aa5548517 100644
--- a/src/cc65/coptpush.h
+++ b/src/cc65/coptpush.h
@@ -52,16 +52,16 @@
 unsigned OptPush1 (CodeSeg* S);
 /* Given a sequence
 **
-**     ldy     #xx
 **     jsr     ldaxysp
 **     jsr     pushax
 **
-** If a/x are not used later, replace that by
+** If a/x are not used later, and Y is known, replace that by
 **
 **     ldy     #xx+2
 **     jsr     pushwysp
+**     ldy     #$00     ; present if later code expects Y = 0
 **
-** saving 3 bytes and several cycles.
+** saving several cycles.
 */
 
 unsigned OptPush2 (CodeSeg* S);