Fixed hangup for loops in jump cascade

git-svn-id: svn://svn.cc65.org/cc65/trunk@1734 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/src/cc65/coptind.c b/src/cc65/coptind.c
index 5adae0a29e4b24a106c5de9064aa9abeeaf1a1bc..0ffbf9e2f8a58b962fe75b3e354248dac558e46e 100644 (file)
--- a/src/cc65/coptind.c
+++ b/src/cc65/coptind.c
@@ -261,7 +261,7 @@ unsigned OptDeadJumps (CodeSeg* S)
 
 
 /*****************************************************************************/
-/*                            Remove dead code                              */
+/*                            Remove dead code                              */
 /*****************************************************************************/
 
 
@@ -278,16 +278,22 @@ unsigned OptDeadCode (CodeSeg* S)
     while (I < CS_GetEntryCount (S)) {
 
        CodeEntry* N;
+        CodeLabel* LN;
 
        /* Get this entry */
        CodeEntry* E = CS_GetEntry (S, I);
 
                /* Check if it's an unconditional branch, and if the next entry has
-        * no labels attached
+        * no labels attached, or if the label is just used so that the insn
+         * can jump to itself.
         */
-               if ((E->Info & OF_DEAD) != 0           &&
-           (N = CS_GetNextEntry (S, I)) != 0  &&
-           !CE_HasLabel (N)) {
+               if ((E->Info & OF_DEAD) != 0                     &&     /* Dead code follows */
+           (N = CS_GetNextEntry (S, I)) != 0            &&     /* Has next entry */
+                   (!CE_HasLabel (N)                        ||         /* Don't has a label */
+             ((N->Info & OF_UBRA) != 0          &&              /* Uncond branch */
+              (LN = N->JumpTo) != 0             &&              /* Jumps to known label */
+              LN->Owner == N                    &&              /* Attached to insn */
+              CL_GetRefCount (LN) == 1))) {                     /* Only reference */
 
            /* Delete the next entry */
            CS_DelEntry (S, I+1);
@@ -352,10 +358,28 @@ unsigned OptJumpCascades (CodeSeg* S)
                        ((E->Info & OF_CBRA) != 0 &&
                 GetBranchCond (E->OPC)  == GetBranchCond (N->OPC))) {
 
-               /* This is a jump cascade and we may jump to the final target.
-                * Insert a new instruction, then remove the old one
+               /* This is a jump cascade and we may jump to the final target,
+                 * provided that the other insn does not jump to itself. If
+                 * this is the case, we can also jump to ourselves, otherwise
+                 * insert a jump to the new instruction and remove the old one.
                 */
-               CodeEntry* X = NewCodeEntry (E->OPC, E->AM, N->Arg, N->JumpTo, E->LI);
+                       CodeEntry* X;
+                CodeLabel* LN = N->JumpTo;
+
+                if (LN != 0 && LN->Owner == N) {
+
+                    /* We found a jump to a jump to itself. Replace our jump
+                     * by a jump to itself.
+                     */
+                    CodeLabel* LE = CS_GenLabel (S, E);
+                    X = NewCodeEntry (E->OPC, E->AM, LE->Name, LE, E->LI);
+
+                } else {
+
+                    /* Jump to the final jump target */
+                    X = NewCodeEntry (E->OPC, E->AM, N->Arg, N->JumpTo, E->LI);
+
+                }
 
                /* Insert it behind E */
                CS_InsertEntry (S, X, I+1);