no TGI_ERR_NO_MEM or TGI_ERR_NO_IOCB anymore: replaced by TGI_ERR_NO_RES

[cc65] / libsrc / runtime / shl.s

diff --git a/libsrc/runtime/shl.s b/libsrc/runtime/shl.s
index 73f48314295a3f9a32482dc580c3c4747dec406d..1963abbdc8a87bec390bf5ae955e28f19b7a5fae 100644 (file)
--- a/libsrc/runtime/shl.s
+++ b/libsrc/runtime/shl.s
@@ -1,69 +1,58 @@
 ;
-; Ullrich von Bassewitz, 05.08.1998
+; Ullrich von Bassewitz, 1998-08-05, 2004-06-25
 ;
-; CC65 runtime: left shift support for ints
+; CC65 runtime: left shift support for ints and unsigneds
 ;
+; Note: The standard declares a shift count that is negative or >= the
+; bitcount of the shifted type for undefined behaviour.
+;
+; Note^2: The compiler knowns about the register/zero page usage of this
+; function, so you need to change the compiler source if you change it!
+;
+
 
-       .export         tosasla0, tosaslax, tosshla0, tosshlax
-       .import         popsreg, return0
-       .importzp       sreg
+       .export         tosaslax, tosshlax
+       .import         popax
+       .importzp       tmp1
 
-tosshla0:
-tosasla0:
-       ldx     #0
 tosshlax:
 tosaslax:
-       jsr     popsreg         ; get TOS into sreg
-       cpx     #0
-       bne     TooLarge
-       cmp     #16
-       bcs     TooLarge
+        and     #$0F            ; Bring the shift count into a valid range
+        sta     tmp1            ; Save it
 
-               cmp     #8              ; Shift count greater 8?
-       beq     L3              ; Jump if exactly 8
-               bcc     L1              ; Jump if no
+        jsr     popax           ; Get the left hand operand
 
-; Shift count is greater 8. Do the first 8 bits the fast way
+        ldy     tmp1            ; Get shift count
+        beq     L9              ; Bail out if shift count zero
 
-       ldy     sreg
-       sty     sreg+1
-               stx     sreg            ; Low byte = 0
-       sec
-       sbc     #8
+        cpy     #8              ; Shift count 8 or greater?
+        bcc     L3              ; Jump if not
 
-; Shift count less than 8 if we come here
+; Shift count is greater 7. The carry is set when we enter here.
 
-L1:    tay                     ; Shift count --> Y
-       beq     Zero            ; Done if shift count zero
+        tax
+        tya
+        sbc     #8
+        tay
+        txa
+        jmp     L2
+L1:     asl     a
+L2:     dey
+        bpl     L1
+        tax
+        lda     #$00
+        rts
 
-       lda     sreg            ; get low byte for faster shift
+; Shift count is less than 8.
 
-; Do the actual shift
-
-L2:            asl     a
-       rol     sreg+1
-       dey
-               bne     L2
+L3:     stx     tmp1            ; Save high byte of lhs
+L4:            asl     a
+       rol     tmp1
+        dey
+               bne     L4
 
 ; Done with shift
 
-       ldx     sreg+1
-       rts
-
-; Shift count == 8
-
-L3:    txa                     ; X == 0, now A == 0
-       ldx     sreg
-       rts
-
-; Shift count was zero
-
-Zero:  lda     sreg
-       ldx     sreg+1
-       rts
-
-; Shift count too large, result is zero
-
-TooLarge:
-       jmp     return0
+        ldx    tmp1
+L9:     rts