Merge pull request #2735 from kugelfuhr/kugelfuhr/fix-2025

Add an optimization that removes compare instructions preceeding RTS or function calls

.github/checks/lastline.sh

@@ -23,3 +23,4 @@ if [ x"$FILES"x != xx ]; then
     done
     exit -1
 fi
+exit 0

.github/checks/lineendings.sh

@@ -16,3 +16,4 @@ if [ x"$FILES"x != xx ]; then
     done
     exit -1
 fi
+exit 0

.github/checks/noexec.sh

@@ -16,3 +16,4 @@ if [ x"$FILES"x != xx ]; then
     done
     exit -1
 fi
+exit 0

.github/checks/sorted.sh

@@ -36,3 +36,4 @@ function checkarray_quoted_name
 for N in `grep -rl "BEGIN SORTED.SH" "$CHECK_DIR"`; do
     checkarray_quoted_name $N
 done
+exit 0

.github/checks/sorted_codeopt.sh

@@ -63,6 +63,7 @@ function checkarray
 }
 
 
-for N in `grep -rl "BEGIN DECL SORTED_CODEOPT.SH" "$CHECK_DIR"`; do
-    checkarray $N
+find "$CHECK_DIR" -name \*.\[ch\] -print | while read N; do
+    grep -q "BEGIN DECL SORTED_CODEOPT.SH" "$N" && checkarray $N
 done
+exit 0	   

.github/checks/sorted_opcodes.sh

@@ -37,4 +37,4 @@ function checkarray_quoted_name
 for N in `grep -rl "BEGIN SORTED_OPCODES.SH" "$CHECK_DIR"`; do
     checkarray_quoted_name $N
 done
-
+exit 0

.github/checks/spaces.sh

@@ -16,3 +16,4 @@ if [ x"$FILES"x != xx ]; then
     done
     exit -1
 fi
+exit 0

.github/checks/tabs.sh

@@ -16,3 +16,4 @@ if [ x"$FILES"x != xx ]; then
     done
     exit -1
 fi
+exit 0

src/cc65/codeopt.c

@@ -133,6 +133,7 @@ static OptFunc DOptCmp2         = { OptCmp2,         "OptCmp2",          85, 0,
 static OptFunc DOptCmp3         = { OptCmp3,         "OptCmp3",          75, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp4         = { OptCmp4,         "OptCmp4",          75, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp5         = { OptCmp5,         "OptCmp5",         100, 0, 0, 0, 0, 0 };
+static OptFunc DOptCmp6         = { OptCmp6,         "OptCmp6",          33, 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 };
@@ -255,6 +256,7 @@ static OptFunc* OptFuncs[] = {
     &DOptCmp3,
     &DOptCmp4,
     &DOptCmp5,
+    &DOptCmp6,
     &DOptCmp7,
     &DOptCmp8,
     &DOptCmp9,
@@ -729,6 +731,7 @@ static unsigned RunOptGroup3 (CodeSeg* S)
         C += RunOptFunc (S, &DOptCondBranch3, 1);
         C += RunOptFunc (S, &DOptCondBranchC, 1);
         C += RunOptFunc (S, &DOptRTSJumps1, 1);
+        C += RunOptFunc (S, &DOptCmp6, 1);          /* After OptRTSJumps1 */
         C += RunOptFunc (S, &DOptBoolCmp, 1);
         C += RunOptFunc (S, &DOptBoolTrans, 1);
         C += RunOptFunc (S, &DOptBNegA2, 1);        /* After OptCondBranch's */

src/cc65/coptcmp.c

@@ -503,6 +503,51 @@ unsigned OptCmp5 (CodeSeg* S)
 
 
 
+unsigned OptCmp6 (CodeSeg* S)
+/* Remove compare instructions before an RTS or an subroutine call that doesn't
+** use the flags.
+*/
+{
+    unsigned Changes = 0;
+    unsigned I;
+
+    /* Walk over the entries */
+    I = 0;
+    while (I < CS_GetEntryCount (S)) {
+
+        CodeEntry* N;
+
+        /* Get next entry */
+        CodeEntry* E = CS_GetEntry (S, I);
+
+        /* Check for a compare followed by something else.
+        ** Note: The test could be improved by checking the flag usage of the
+        ** function explicitly against the flags set by the compare instruction.
+        ** For current code generation this makes no difference, however.
+        */
+        if ((E->Info & OF_CMP) != 0                     &&
+            (N = CS_GetNextEntry (S, I)) != 0           &&
+            (N->OPC == OP65_RTS                 ||  /* Either RTS, or ... */
+             (N->OPC == OP65_JSR            &&      /* ... or JSR ... */
+              N->JumpTo == 0                &&      /* ... to external ... */
+              (N->Use & PSTATE_ALL) == 0    &&      /* ... with no flags used ... */
+              (N->Chg & PSTATE_ALL) == PSTATE_ALL))) {  /* ... but all destroyed */
+
+            /* Found, remove the compare */
+            CS_DelEntry (S, I);
+            ++Changes;
+        }
+
+        /* Next entry */
+        ++I;
+    }
+
+    /* Return the number of changes made */
+    return Changes;
+}
+
+
+
 unsigned OptCmp7 (CodeSeg* S)
 /* Search for a sequence ldx/txa/branch and remove the txa if A is not
 ** used later.

src/cc65/coptcmp.h

@@ -123,6 +123,11 @@ unsigned OptCmp5 (CodeSeg* S);
 **      jne/jeq L2
 */
 
+unsigned OptCmp6 (CodeSeg* S);
+/* Remove compare instructions before an RTS or an exit by jumping to some
+** other function.
+*/
+
 unsigned OptCmp7 (CodeSeg* S);
 /* Search for a sequence ldx/txa/branch and remove the txa if A is not
 ** used later.