fix code for bitwise shifts by zero

compiler/res/prog8lib/math.asm

@@ -847,67 +847,79 @@ mul_word_640	.proc
 ; support for bit shifting that is too large to be unrolled:
 
 lsr_byte_A	.proc
-		; -- lsr signed byte in A times the value in Y (>1)
+		; -- lsr signed byte in A times the value in Y
+		cpy  #0
+		beq  +
 		cmp  #0
 		bpl  lsr_ubyte_A
 -       	sec
 		ror  a
 		dey
 		bne  -
-		rts
++		rts
 		.pend
 
 lsr_ubyte_A	.proc
-		; -- lsr unsigned byte in A times the value in Y (>1)
+		; -- lsr unsigned byte in A times the value in Y
+		cpy  #0
+		beq  +
 -		lsr  a
 		dey
 		bne  -
-		rts
++		rts
 		.pend
 
 asl_byte_A      .proc
-		; -- asl any byte in A times the value in Y (>1)
+		; -- asl any byte in A times the value in Y
+		cpy  #0
+		beq  +
 -		asl  a
 		dey
 		bne  -
-		rts
++		rts
 		.pend
 
 
 lsr_word_AY     .proc
-		; -- lsr signed word in AY times the value in X (>1)
+		; -- lsr signed word in AY times the value in X
+		cpx  #0
+		beq  +
 		cpy  #0
 		bpl  lsr_uword_AY
 		sty  P8ZP_SCRATCH_B1
-_negative       sec
+-		sec
 		ror  P8ZP_SCRATCH_B1
 		ror  a
 		dex
-		bne  _negative
+		bne  -
 		ldy  P8ZP_SCRATCH_B1
-		rts
++		rts
 		.pend
 
 lsr_uword_AY    .proc
-		; -- lsr unsigned word in AY times the value in X (>1)
+		; -- lsr unsigned word in AY times the value in X
+		cpx  #0
+		beq  +
 		sty  P8ZP_SCRATCH_B1
 -		lsr  P8ZP_SCRATCH_B1
 		ror  a
 		dex
 		bne  -
 		ldy  P8ZP_SCRATCH_B1
-		rts
++		rts
 		.pend
 
 asl_word_AY     .proc
-		; -- asl any word in AY times the value in X (>1)
+		; -- asl any word in AY times the value in X
+		cpx  #0
+		beq  +
 		sty  P8ZP_SCRATCH_B1
 -               asl  a
 		rol  P8ZP_SCRATCH_B1
 		dex
 		bne  -
 		ldy  P8ZP_SCRATCH_B1
-		rts
++		rts
 		.pend
 
 

examples/test.p8

@@ -1,8 +1,16 @@
+%import textio
+%zeropage basicsafe
+
 main {
     sub start() {
-        print('@')
+        ubyte value = 1
-    }
+        uword wvalue = 1
-
+        ubyte zero = 0
-    sub print(str message) {
+        txt.print_ub(value<<zero)       ; TODO fix result 6502 codegen! should be 1.
+        txt.print_uw(wvalue<<zero)      ; TODO fix result 6502 codegen! should be 1.
+        ubyte value2 = value<<zero      ; result is ok, 1
+        uword wvalue2 = wvalue<<zero    ; result is ok, 1
+        txt.print_ub(value2)
+        txt.print_uw(wvalue2)
     }
 }