Optimize local immidiate stores

git-svn-id: svn://svn.cc65.org/cc65/trunk@556 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/src/cc65/optimize.c b/src/cc65/optimize.c
index 5fa0ad5612b36f0c4cd50013d686114fe92c6215..55ebe9761f16e3add1fc0bf31b495b5ee5b25dc6 100644 (file)
--- a/src/cc65/optimize.c
+++ b/src/cc65/optimize.c
@@ -1719,8 +1719,42 @@ static void OptLoads (void)
 
            /* Remove the remaining lines */
            FreeLines (L2[1], L2[2]);
-       }
 
+       /* Search for:
+        *
+        *      ldx     xx
+        *      lda     yy
+        *      jsr     stax0sp
+        *
+        * and replace it by:
+        *
+        *      lda     xx
+        *      ldy     #$01
+        *      sta     (sp),y
+                *      dey
+        *      lda     yy
+        *      sta     (sp),y
+        *
+        * provided that that the X register is not used later. This code
+        * sequence is four bytes longer, but a lot faster and it does not
+        * use the X register, so other loads may get removed later.
+        */
+               } else if (LineMatch (L, "\tldx\t")             &&
+                   GetNextCodeLines (L, L2, 2)                 &&
+           LineMatch (L2 [0], "\tlda\t")               &&
+                   LineFullMatch (L2 [1], "\tjsr\tstax0sp")    &&
+           !RegXUsed (L2[1])) {
+
+           /* Found - replace it */
+           L->Line[3] = 'a';
+           L = NewLineAfter (L, "\tldy\t#$01");
+           L = NewLineAfter (L, "\tsta\t(sp),y");
+           L = NewLineAfter (L, "\tdey");
+           L = NewLineAfter (L2[0], "\tsta\t(sp),y");
+
+           /* Remove the remaining line */
+           FreeLine (L2[1]);
+       }
 
                /* All other patterns start with this one: */
        if (!LineFullMatch (L, "\tldx\t#$00")) {