From: cuz <cuz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Thu, 21 Nov 2002 01:08:14 +0000 (+0000)
Subject: Small but significant shift optimization
X-Git-Tag: V2.12.0~2074
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=0ba44bb2d4b3203f322170b51792ac98bab1a23e;p=cc65

Small but significant shift optimization


git-svn-id: svn://svn.cc65.org/cc65/trunk@1559 b7a2c559-68d2-44c3-8de9-860c34a00d81
---

diff --git a/src/cc65/codeopt.c b/src/cc65/codeopt.c
index a1d824d0a..01bba7b42 100644
--- a/src/cc65/codeopt.c
+++ b/src/cc65/codeopt.c
@@ -138,13 +138,18 @@ static unsigned OptShift1 (CodeSeg* S)
 
 static unsigned OptShift2 (CodeSeg* S)
 /* A call to the shraxN routine may get replaced by one or more lsr insns
- * if the value of X is not used later.
+ * if the value of X is not used later, or if the value of X is known and
+ * zero.
  */
 {
     unsigned Changes = 0;
+    unsigned I;
+
+    /* Generate register info */
+    CS_GenRegInfo (S);
 
     /* Walk over the entries */
-    unsigned I = 0;
+    I = 0;
     while (I < CS_GetEntryCount (S)) {
 
       	/* Get next entry */
@@ -155,13 +160,13 @@ static unsigned OptShift2 (CodeSeg* S)
        	    strncmp (E->Arg, "shrax", 5) == 0        &&
 	    strlen (E->Arg) == 6                     &&
 	    IsDigit (E->Arg[5])                      &&
-	    !RegXUsed (S, I+1)) {
+       	    (E->RI->In.RegX == 0 || !RegXUsed (S, I+1))) {
 
 	    /* Insert shift insns */
 	    unsigned Count = E->Arg[5] - '0';
 	    while (Count--) {
 	    	CodeEntry* X = NewCodeEntry (OP65_LSR, AM65_ACC, "a", 0, E->LI);
-	    	CS_InsertEntry (S, X, I+1);
+    	    	CS_InsertEntry (S, X, I+1);
 	    }
 
 	    /* Delete the call to shlax */
@@ -177,6 +182,9 @@ static unsigned OptShift2 (CodeSeg* S)
 
     }
 
+    /* Free the register info */
+    CS_FreeRegInfo (S);
+
     /* Return the number of changes made */
     return Changes;
 }