From 0647cb11120381e3ec892f199a77f9524aebcef2 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Sun, 20 Jul 2025 12:54:09 +0200
Subject: [PATCH] Merge jsr pushax/j?? popax into nothing or RTS

---
 src/cc65/codeopt.c  |  5 ++++-
 src/cc65/coptmisc.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
 src/cc65/coptmisc.h |  3 ++-
 3 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/src/cc65/codeopt.c b/src/cc65/codeopt.c
index 728e76d88..326fe8d48 100644
--- a/src/cc65/codeopt.c
+++ b/src/cc65/codeopt.c
@@ -218,6 +218,7 @@ static OptFunc DOptSub3         = { OptSub3,         "OptSub3",         100, 0,
 static OptFunc DOptTest1        = { OptTest1,        "OptTest1",         65, 0, 0, 0, 0, 0 };
 static OptFunc DOptTest2        = { OptTest2,        "OptTest2",         50, 0, 0, 0, 0, 0 };
 static OptFunc DOptTosLoadPop   = { OptTosLoadPop,   "OptTosLoadPop",    50, 0, 0, 0, 0, 0 };
+static OptFunc DOptTosPushPop   = { OptTosPushPop,   "OptTosPushPop",    33, 0, 0, 0, 0, 0 };
 static OptFunc DOptTransfers1   = { OptTransfers1,   "OptTransfers1",     0, 0, 0, 0, 0, 0 };
 static OptFunc DOptTransfers2   = { OptTransfers2,   "OptTransfers2",    60, 0, 0, 0, 0, 0 };
 static OptFunc DOptTransfers3   = { OptTransfers3,   "OptTransfers3",    65, 0, 0, 0, 0, 0 };
@@ -344,11 +345,12 @@ static OptFunc* OptFuncs[] = {
     &DOptSub3,
     &DOptTest1,
     &DOptTest2,
+    &DOptTosLoadPop,
+    &DOptTosPushPop,
     &DOptTransfers1,
     &DOptTransfers2,
     &DOptTransfers3,
     &DOptTransfers4,
-    &DOptTosLoadPop,
     &DOptUnusedLoads,
     &DOptUnusedStores,
 /* END SORTED_CODEOPT.SH */
@@ -924,6 +926,7 @@ static unsigned RunOptGroup7 (CodeSeg* S)
     /* Re-optimize JSR/RTS that may now be grouped */
     C += RunOptFunc (S, &DOptRTS, 1);
     C += RunOptFunc (S, &DOptTosLoadPop, 5);
+    C += RunOptFunc (S, &DOptTosPushPop, 5);
 
     Changes += C;
     /* If we had changes, we must run dead code elimination again,
diff --git a/src/cc65/coptmisc.c b/src/cc65/coptmisc.c
index 0110dae4e..0e3dd0d56 100644
--- a/src/cc65/coptmisc.c
+++ b/src/cc65/coptmisc.c
@@ -1201,3 +1201,54 @@ unsigned OptBinOps2 (CodeSeg* S)
     /* Return the number of changes made */
     return Changes;
 }
+
+
+unsigned OptTosPushPop(CodeSeg *S)
+/* Merge jsr pushax/j?? popax */
+{
+    unsigned Changes = 0;
+    unsigned I;
+
+    /* Walk over the entries */
+    I = 0;
+    while (I < CS_GetEntryCount (S)) {
+
+        const CodeEntry* N;
+
+        /* Get the next entry */
+        const CodeEntry* E = CS_GetEntry (S, I);
+
+        /* Check for decspn, incspn, subysp or addysp */
+        if (E->OPC == OP65_JSR                            &&
+            strcmp(E->Arg, "pushax") == 0                 &&
+            (N = CS_GetNextEntry (S, I)) != 0             &&
+            (N->OPC == OP65_JSR || N->OPC == OP65_JMP)    &&
+            strcmp(N->Arg, "popax") == 0                  &&
+            !CE_HasLabel (N)) {
+
+            /* Delete the old code */
+            CS_DelEntries (S, I, 2);
+
+            /* Insert an rts if jmp popax */
+            if (N->OPC == OP65_JMP) {
+              CodeEntry* X = NewCodeEntry (OP65_RTS, AM65_IMP, 0, 0, E->LI);
+              CS_InsertEntry (S, X, I);
+            }
+
+            /* Regenerate register info */
+            CS_GenRegInfo (S);
+
+            /* Remember we had changes */
+            ++Changes;
+
+        } else {
+
+            /* Next entry */
+            ++I;
+        }
+
+    }
+
+    /* Return the number of changes made */
+    return Changes;
+}
diff --git a/src/cc65/coptmisc.h b/src/cc65/coptmisc.h
index ea678ea67..64c310d20 100644
--- a/src/cc65/coptmisc.h
+++ b/src/cc65/coptmisc.h
@@ -134,7 +134,8 @@ unsigned OptBinOps2 (CodeSeg* S);
 unsigned OptTosLoadPop (CodeSeg* S);
 /* Merge jsr ldax0sp / jsr|jmp incsp2 into jsr|jmp popax */
 
-
+unsigned OptTosPushPop(CodeSeg *S);
+/* Merge jsr pushax/j?? popax */
 
 /* End of coptmisc.h */