From 52a368adc163f9a87e77a617c44c1b2666138072 Mon Sep 17 00:00:00 2001
From: uz <uz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Mon, 14 Sep 2009 22:02:48 +0000
Subject: [PATCH] Improved the code that checks for memory accesses. The old
 code didn't detect certain accesses.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4174 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 src/cc65/coptind.c | 72 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 56 insertions(+), 16 deletions(-)

diff --git a/src/cc65/coptind.c b/src/cc65/coptind.c
index 578a72c7f..2dd0aaa54 100644
--- a/src/cc65/coptind.c
+++ b/src/cc65/coptind.c
@@ -51,27 +51,67 @@
 
 
 
-static int MemAccess (CodeSeg* S, unsigned From, unsigned To, const char* Arg)
-/* Checks a range of code entries if there are any memory accesses to Arg.
- * Note: This function is not 100% safe, because there is more than one way
- * to express a memory location ("foo" and "foo+0" comes to mind) and there
- * may be other accesses through pointers. For the code generated by cc65 and
- * for the purpose of the caller (OptPushPop) it is assumed to be safe enough
- * however.
- */
+static int MemAccess (CodeSeg* S, unsigned From, unsigned To, const CodeEntry* N)
+/* Checks a range of code entries if there are any memory accesses to N->Arg */
 {
+    /* Get the length of the argument */
+    unsigned NLen = strlen (N->Arg);
+
+    /* What to check for? */
+    enum {
+        None    = 0x00,
+        Base    = 0x01,         /* Check for location without "+1" */
+        Word    = 0x02,         /* Check for location with "+1" added */
+    } What = None;
+
+
+    /* If the argument of N is a zero page location that ends with "+1", we
+     * must also check for word accesses to the location without +1.
+     */
+    if (N->AM == AM65_ZP && NLen > 2 && strcmp (N->Arg + NLen - 2, "+1") == 0) {
+        What |= Base;
+    }
+
+    /* If the argument is zero page indirect, we must also check for accesses
+     * to "arg+1"
+     */
+    if (N->AM == AM65_ZP_INDY || N->AM == AM65_ZPX_IND || N->AM == AM65_ZP_IND) {
+        What |= Word;
+    }
+
     /* Walk over all code entries */
     while (From <= To) {
 
 	/* Get the next entry */
 	CodeEntry* E = CS_GetEntry (S, From);
 
-        /* For simplicity, we just check if there is an argument and if this
-         * argument equals Arg.
+        /* Check if there is an argument and if this argument equals Arg in
+         * some variants.
          */
-        if (E->Arg && strcmp (E->Arg, Arg) == 0) {
-            /* Found an access */
-            return 1;
+        if (E->Arg[0] != '\0') {
+
+            unsigned ELen;
+
+            if (strcmp (E->Arg, N->Arg) == 0) {
+                /* Found an access */
+                return 1;
+            }
+
+            ELen = strlen (E->Arg);
+            if ((What & Base) != 0) {
+                if (ELen == NLen - 2 && strncmp (E->Arg, N->Arg, NLen-2) == 0) {
+                    /* Found an access */
+                    return 1;
+                }
+            }
+
+            if ((What & Word) != 0) {
+                if (ELen == NLen + 2 && strncmp (E->Arg, N->Arg, NLen) == 0 &&
+                    E->Arg[NLen] == '+' && E->Arg[NLen+1] == '1') {
+                    /* Found an access */
+                    return 1;
+                }
+            }
         }
 
         /* Next entry */
@@ -1480,7 +1520,7 @@ unsigned OptTransfers3 (CodeSeg* S)
                      StoreEntry->AM == AM65_ZP)                                 &&
                     (StoreEntry->AM != AM65_ZP ||
                      (StoreEntry->Chg & UsedRegs) == 0)                         &&
-                    !MemAccess (S, Xfer+1, Store-1, StoreEntry->Arg)) {
+                    !MemAccess (S, Xfer+1, Store-1, StoreEntry)) {
 
                     /* Generate the replacement store insn */
                     CodeEntry* X = 0;
@@ -1645,7 +1685,7 @@ unsigned OptTransfers4 (CodeSeg* S)
                     (LoadEntry->AM == AM65_ABS          ||
                      LoadEntry->AM == AM65_ZP           ||
                      LoadEntry->AM == AM65_IMM)                                 &&
-                    !MemAccess (S, Load+1, Xfer-1, LoadEntry->Arg)) {
+                    !MemAccess (S, Load+1, Xfer-1, LoadEntry)) {
 
                     /* Generate the replacement load insn */
                     CodeEntry* X = 0;
@@ -1794,7 +1834,7 @@ unsigned OptPushPop (CodeSeg* S)
                  */
                 if (E->OPC == OP65_STA                  &&
                     !RegAUsed (S, I+1)                  &&
-                    !MemAccess (S, Push+1, Pop-1, E->Arg)) {
+                    !MemAccess (S, Push+1, Pop-1, E)) {
 
                     /* Insert a STA after the PHA */
                     X = NewCodeEntry (E->OPC, E->AM, E->Arg, E->JumpTo, E->LI);
-- 
2.39.5