From: uz <uz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Sat, 29 Aug 2009 11:31:28 +0000 (+0000)
Subject: Another tiny code improvement for integer compares.
X-Git-Tag: V2.13.0rc1~185
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=82919fa2f8eb5baf6d859f8334271d63fd848660;p=cc65

Another tiny code improvement for integer compares.


git-svn-id: svn://svn.cc65.org/cc65/trunk@4071 b7a2c559-68d2-44c3-8de9-860c34a00d81
---

diff --git a/src/cc65/codeopt.c b/src/cc65/codeopt.c
index 8a8c945d0..abd5fdb63 100644
--- a/src/cc65/codeopt.c
+++ b/src/cc65/codeopt.c
@@ -1097,6 +1097,7 @@ static OptFunc DOptCmp5	       	= { OptCmp5,   	     "OptCmp5",        	100, 0,
 static OptFunc DOptCmp6	       	= { OptCmp6,   	     "OptCmp6",        	100, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp7	       	= { OptCmp7,   	     "OptCmp7",        	 85, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp8	       	= { OptCmp8,   	     "OptCmp8",        	 50, 0, 0, 0, 0, 0 };
+static OptFunc DOptCmp9	       	= { OptCmp9,   	     "OptCmp9",        	 85, 0, 0, 0, 0, 0 };
 static OptFunc DOptCondBranches1= { OptCondBranches1,"OptCondBranches1", 80, 0, 0, 0, 0, 0 };
 static OptFunc DOptCondBranches2= { OptCondBranches2,"OptCondBranches2",  0, 0, 0, 0, 0, 0 };
 static OptFunc DOptDeadCode    	= { OptDeadCode,     "OptDeadCode",    	100, 0, 0, 0, 0, 0 };
@@ -1182,6 +1183,7 @@ static OptFunc* OptFuncs[] = {
     &DOptCmp6,
     &DOptCmp7,
     &DOptCmp8,
+    &DOptCmp9,
     &DOptCondBranches1,
     &DOptCondBranches2,
     &DOptDeadCode,
@@ -1572,6 +1574,7 @@ static unsigned RunOptGroup3 (CodeSeg* S)
        	C += RunOptFunc (S, &DOptCmp6, 1);
        	C += RunOptFunc (S, &DOptCmp7, 1);
        	C += RunOptFunc (S, &DOptCmp8, 1);
+       	C += RunOptFunc (S, &DOptCmp9, 1);
        	C += RunOptFunc (S, &DOptTest1, 1);
         C += RunOptFunc (S, &DOptLoad1, 1);
        	C += RunOptFunc (S, &DOptUnusedLoads, 1);
diff --git a/src/cc65/coptcmp.c b/src/cc65/coptcmp.c
index 881605ecc..cd01c3b29 100644
--- a/src/cc65/coptcmp.c
+++ b/src/cc65/coptcmp.c
@@ -6,8 +6,8 @@
 /*                                                                           */
 /*                                                                           */
 /*                                                                           */
-/* (C) 2001-2005, Ullrich von Bassewitz                                      */
-/*                Römerstrasse 52                                            */
+/* (C) 2001-2009, Ullrich von Bassewitz                                      */
+/*                Roemerstrasse 52                                           */
 /*                D-70794 Filderstadt                                        */
 /* EMail:         uz@cc65.org                                                */
 /*                                                                           */
@@ -920,4 +920,73 @@ NextEntry:
 
 
 
+unsigned OptCmp9 (CodeSeg* S)
+/* Search for the sequence
+ *
+ *    sbc       xx
+ *    bvs/bvc   L
+ *    eor       #$80
+ * L: asl       a
+ *    bcc/bcs   somewhere
+ *
+ * If A is not used later (which should be the case), we can branch on the N
+ * flag instead of the carry flag and remove the asl.
+ */
+{
+    unsigned Changes = 0;
+    unsigned I;
+
+    /* Walk over the entries */
+    I = 0;
+    while (I < CS_GetEntryCount (S)) {
+
+       	CodeEntry* L[5];
+
+      	/* Get next entry */
+       	L[0] = CS_GetEntry (S, I);
+
+     	/* Check for the sequence */
+       	if (L[0]->OPC == OP65_SBC                       &&
+       	    CS_GetEntries (S, L+1, I+1, 4)	        &&
+            (L[1]->OPC == OP65_BVC              ||
+             L[1]->OPC == OP65_BVS)                     &&
+            L[1]->JumpTo != 0                           &&
+            L[1]->JumpTo->Owner == L[3]                 &&
+            L[2]->OPC == OP65_EOR                       &&
+            CE_IsKnownImm (L[2], 0x80)                  &&
+            L[3]->OPC == OP65_ASL                       &&
+            L[3]->AM == AM65_ACC                        &&
+            (L[4]->OPC == OP65_BCC              ||
+             L[4]->OPC == OP65_BCS              ||
+             L[4]->OPC == OP65_JCC              ||
+             L[4]->OPC == OP65_JCS)                     &&
+            !CE_HasLabel (L[4])                         &&
+            !RegAUsed (S, I+4)) {
+
+	    /* Replace the branch condition */
+	    switch (GetBranchCond (L[4]->OPC)) {
+                case BC_CC:     CE_ReplaceOPC (L[4], OP65_JPL); break;
+                case BC_CS:     CE_ReplaceOPC (L[4], OP65_JMI); break;
+                default:        Internal ("Unknown branch condition in OptCmp9");
+            }
+
+            /* Delete the asl insn */
+            CS_DelEntry (S, I+3);
+
+            /* Next sequence is somewhat ahead (if any) */
+            I += 3;
+
+            /* Remember, we had changes */
+            ++Changes;
+	}
+
+     	/* Next entry */
+	++I;
+    }
+
+    /* Return the number of changes made */
+    return Changes;
+}
+
+
 
diff --git a/src/cc65/coptcmp.h b/src/cc65/coptcmp.h
index 39a79121f..7efbeada8 100644
--- a/src/cc65/coptcmp.h
+++ b/src/cc65/coptcmp.h
@@ -6,10 +6,10 @@
 /*                                                                           */
 /*                                                                           */
 /*                                                                           */
-/* (C) 2001-2004 Ullrich von Bassewitz                                       */
-/*               Römerstrasse 52                                             */
-/*               D-70794 Filderstadt                                         */
-/* EMail:        uz@cc65.org                                                 */
+/* (C) 2001-2009, Ullrich von Bassewitz                                      */
+/*                Roemerstrasse 52                                           */
+/*                D-70794 Filderstadt                                        */
+/* EMail:         uz@cc65.org                                                */
 /*                                                                           */
 /*                                                                           */
 /* This software is provided 'as-is', without any expressed or implied       */
@@ -153,6 +153,19 @@ unsigned OptCmp8 (CodeSeg* S);
  * the result of the compare is known.
  */
 
+unsigned OptCmp9 (CodeSeg* S);
+/* Search for the sequence
+ *
+ *    sbc       xx
+ *    bvs/bvc   L
+ *    eor       #$80
+ * L: asl       a
+ *    bcc/bcs   somewhere
+ *
+ * If A is not used later (which should be the case), we can branch on the N
+ * flag instead of the carry flag and remove the asl.
+ */
+
 
 
 /* End of coptcmp.h */