Added another optimization

git-svn-id: svn://svn.cc65.org/cc65/trunk@1044 b7a2c559-68d2-44c3-8de9-860c34a00d81

src/cc65/codeopt.c

@@ -1369,7 +1369,8 @@ static OptFunc DOptDupLoads     = { OptDupLoads,     "OptDupLoads",     0, 0, 0,
 static OptFunc DOptJumpCascades	= { OptJumpCascades, "OptJumpCascades", 0, 0, 0, 0, 0 };
 static OptFunc DOptJumpTarget  	= { OptJumpTarget,   "OptJumpTarget",   0, 0, 0, 0, 0 };
 static OptFunc DOptRTS 	       	= { OptRTS,    	     "OptRTS",       	0, 0, 0, 0, 0 };
-static OptFunc DOptRTSJumps    	= { OptRTSJumps,     "OptRTSJumps",  	0, 0, 0, 0, 0 };
+static OptFunc DOptRTSJumps1    = { OptRTSJumps1,    "OptRTSJumps1",  	0, 0, 0, 0, 0 };
+static OptFunc DOptRTSJumps2    = { OptRTSJumps2,    "OptRTSJumps2",  	0, 0, 0, 0, 0 };
 static OptFunc DOptNegA1       	= { OptNegA1,  	     "OptNegA1",     	0, 0, 0, 0, 0 };
 static OptFunc DOptNegA2       	= { OptNegA2,  	     "OptNegA2",     	0, 0, 0, 0, 0 };
 static OptFunc DOptNegAX1      	= { OptNegAX1,       "OptNegAX1",    	0, 0, 0, 0, 0 };
@@ -1434,7 +1435,8 @@ static OptFunc* OptFuncs[] = {
     &DOptPtrStore1,
     &DOptPtrStore2,
     &DOptRTS,
-    &DOptRTSJumps,
+    &DOptRTSJumps1,
+    &DOptRTSJumps2,
     &DOptShift1,
     &DOptShift2,
     /*&DOptSize1,*/
@@ -1726,7 +1728,7 @@ static void RunOptGroup3 (CodeSeg* S)
        	Changes += RunOptFunc (S, &DOptDeadCode, 1);
        	Changes += RunOptFunc (S, &DOptJumpTarget, 1);
 	Changes += RunOptFunc (S, &DOptCondBranches, 1);
-	Changes += RunOptFunc (S, &DOptRTSJumps, 1);
+	Changes += RunOptFunc (S, &DOptRTSJumps1, 1);
 	Changes += RunOptFunc (S, &DOptBoolTrans, 1);
 	Changes += RunOptFunc (S, &DOptCmp1, 1);
 	Changes += RunOptFunc (S, &DOptCmp2, 1);
@@ -1762,8 +1764,15 @@ static void RunOptGroup4 (CodeSeg* S)
      */
     RunOptFunc (S, &DOptJumpTarget, 5);
 
-    /* Finally, adjust branch distances */
+    /* Adjust branch distances */
     RunOptFunc (S, &DOptBranchDist, 3);
+
+    /* Replace conditional branches to RTS. If we had changes, we must run dead
+     * code elimination again, since the change may have introduced dead code.
+     */
+    if (RunOptFunc (S, &DOptRTSJumps2, 1)) {
+	RunOptFunc (S, &DOptDeadCode, 1);
+    }
 }
 
 

src/cc65/coptind.c

@@ -48,7 +48,7 @@
 
 
 
-unsigned OptRTSJumps (CodeSeg* S)
+unsigned OptRTSJumps1 (CodeSeg* S)
 /* Replace jumps to RTS by RTS */
 {
     unsigned Changes = 0;
@@ -88,6 +88,64 @@ unsigned OptRTSJumps (CodeSeg* S)
 
 
 
+unsigned OptRTSJumps2 (CodeSeg* S)
+/* Replace long conditional jumps to RTS */
+{
+    unsigned Changes = 0;
+
+    /* Walk over all entries minus the last one */
+    unsigned I = 0;
+    while (I < CS_GetEntryCount (S)) {
+
+	CodeEntry* N;
+
+	/* Get the next entry */
+	CodeEntry* E = CS_GetEntry (S, I);
+
+       	/* Check if it's an unconditional branch to a local target */
+       	if ((E->Info & OF_CBRA) != 0 		&&   /* Conditional branch */
+	    (E->Info & OF_LBRA) != 0            &&   /* Long branch */
+	    E->JumpTo != 0    			&&   /* Local label */
+	    E->JumpTo->Owner->OPC == OP65_RTS   &&   /* Target is an RTS */
+	    (N = CS_GetNextEntry (S, I)) != 0) {     /* There is a next entry */
+
+	    CodeEntry* X;
+	    CodeLabel* LN;
+	    opc_t      NewBranch;
+
+	    /* We will create a jump around an RTS instead of the long branch */
+	    X = NewCodeEntry (OP65_RTS, AM65_IMP, 0, 0, E->JumpTo->Owner->LI);
+	    CS_InsertEntry (S, X, I+1);
+
+	    /* Get the new branch opcode */
+	    NewBranch = MakeShortBranch (GetInverseBranch (E->OPC));
+
+	    /* Get the label attached to N, create a new one if needed */
+	    LN = CS_GenLabel (S, N);
+
+	    /* Generate the branch */
+	    X = NewCodeEntry (NewBranch, AM65_BRA, LN->Name, LN, E->LI);
+	    CS_InsertEntry (S, X, I+1);
+
+	    /* Delete the long branch */
+	    CS_DelEntry (S, I);
+
+	    /* Remember, we had changes */
+	    ++Changes;
+
+	}
+
+	/* Next entry */
+	++I;
+
+    }
+
+    /* Return the number of changes made */
+    return Changes;
+}
+
+
+
 /*****************************************************************************/
 /*	      	  	       Remove dead jumps		      	     */
 /*****************************************************************************/

src/cc65/coptind.h

@@ -49,9 +49,12 @@
 
 
 
-unsigned OptRTSJumps (CodeSeg* S);
+unsigned OptRTSJumps1 (CodeSeg* S);
 /* Replace jumps to RTS by RTS */
 
+unsigned OptRTSJumps2 (CodeSeg* S);
+/* Replace long conditional jumps to RTS */
+
 unsigned OptDeadJumps (CodeSeg* S);
 /* Remove dead jumps (jumps to the next instruction) */