Reestablished entry state of signed operation and optimized that (again).

libsrc/runtime/absvaludiv16.s

@@ -1,22 +0,0 @@
-;
-; Christian Krueger, 23-May-2018
-;
-; CC65 runtime: helper call for mod/div with signed ints
-;
-; When negating values, we will ignore the possibility here, that one of the
-; values is $8000, in which case the negate will fail.
-
-        .export         absvaludiv16
-        .import         _abs, popax, udiv16
-        .importzp       ptr1, ptr4
-
-
-absvaludiv16:
-        jsr     _abs
-        sta     ptr4
-        stx     ptr4+1          ; Save right absolute operand      
-        jsr     popax
-        jsr     _abs
-        sta     ptr1
-        stx     ptr1+1          ; Save left absolute operand  
-        jmp     udiv16

libsrc/runtime/div.s

@@ -1,5 +1,5 @@
 ;
-; Christian Krueger, 24-May-2018
+; Ullrich von Bassewitz, 07.08.1998
 ;
 ; CC65 runtime: division for signed ints
 ;
@@ -8,22 +8,30 @@
 ; values is $8000, in which case the negate will fail.
 
         .export         tosdiva0, tosdivax
-        .import         absvaludiv16, negax
+        .import         popsargsudiv16, negax
-        .importzp       sp, ptr1, tmp1
+        .importzp       ptr1, tmp1, tmp2
 
 tosdiva0:
         ldx     #0
 tosdivax:
-        pha                         ; Check if high-bytes indicate
+        jsr     popsargsudiv16  ; Get arguments from stack, adjust sign
-        txa                         ; different sign, so that we have to
+                                ; and do the division
-        ldy     #1                  ; negate the result after the operation.
+        ldx     ptr1+1          ; Load high byte of result
-        eor     (sp),y              ; Eor with lhs high byte
+
-        sta     tmp1                ; Save post negation indicator to tmp1
+; Adjust the sign of the result. tmp1 contains the high byte of the left
-        pla                         ; Back to entry accu
+; operand, tmp2 contains the high byte of the right operand.
-        jsr     absvaludiv16
+
-        ldx     ptr1+1
+        lda     tmp1
-        lda     ptr1
+        eor     tmp2
-        ldy     tmp1                ; Fetch indicator
+        bpl     Pos             ; Jump if sign of result positive
-        bmi     negate
+
+; Result is negative
+
+        lda     ptr1            ; Load low byte of result
+        jmp     negax           ; Adjust the sign
+
+; Result is positive
+
+Pos:    lda     ptr1            ; Load low byte of result
         rts
-negate: jmp     negax
+

libsrc/runtime/mod.s

@@ -1,5 +1,5 @@
 ;
-; Christian Krueger, 24-May-2018
+; Ullrich von Bassewitz, 07.08.1998
 ;
 ; CC65 runtime: modulo operation for signed ints
 ;
@@ -8,25 +8,30 @@
 ; values is $8000, in which case the negate will fail.
 
         .export         tosmoda0, tosmodax
-        .import         absvaludiv16, negax
+        .import         popsargsudiv16, negax
-        .importzp       sp, sreg, tmp1
+        .importzp       sreg, tmp1
 
 tosmoda0:
         ldx     #0
 tosmodax:
+        jsr     popsargsudiv16  ; Get arguments from stack, adjust sign
+                                ; and do the division
+        lda     sreg            ; Load low byte of result
+        ldx     sreg+1          ; Load high byte of result
 
-; Prepare adjustment of the sign of the result. The sign of the result of the
+; Adjust the sign of the result. tmp1 contains the high byte of the left
-; modulo operation is the same as that of the left operand.
+; operand, tmp2 contains the high byte of the right operand. The sign of
+; the result of the modulo operation is the same as that of the left
+; operand
+
+        bit     tmp1
+        bpl     Pos             ; Jump if sign of result positive
+
+; Result is negative
+
+        jmp     negax           ; Adjust the sign
+
+; Result is positive
+
+Pos:    rts
 
-        pha                         
-        ldy     #1                  ; Prepare lhs operant hi-byte fetch
-        lda     (sp),y             
-        sta     tmp1                ; Save post negation indicator to tmp1
-        pla                         ; Back to entry accu
-        jsr     absvaludiv16
-        ldx     sreg+1              ; Remainder to return registers
-        lda     sreg
-        ldy     tmp1                ; Fetch indicator
-        bmi     negate
-        rts
-negate: jmp     negax

libsrc/runtime/shelp.s

@@ -0,0 +1,29 @@
+;
+; Ullrich von Bassewitz, 07.08.1998
+;
+; CC65 runtime: helper stuff for mod/div with signed ints
+;
+
+; When negating values, we will ignore the possibility here, that one of the
+; values is $8000, in which case the negate will fail.
+
+        .export         popsargsudiv16
+        .import         negax, popax, udiv16
+        .importzp       tmp1, tmp2, ptr1, ptr4
+
+popsargsudiv16:
+        stx     tmp2            ; Remember sign
+        cpx     #0
+        bpl     L1
+        jsr     negax           ; Negate accumulator
+L1:     sta     ptr4
+        stx     ptr4+1          ; Save right operand
+
+        jsr     popax
+        stx     tmp1            ; Remember sign
+        cpx     #0
+        bpl     L2
+        jsr     negax
+L2:     sta     ptr1
+        stx     ptr1+1
+        jmp     udiv16            ; Call the division