more multiplication/division work

c64/basic/math/bb12.div_FAC2_FAC1.s

@@ -34,7 +34,7 @@ div_FAC2_FAC1:
 	// Handle special case - dividing 0 by non-zero value
 
 	lda FAC2_exponent
-	beq div_FAC2_FAC1_setexp_quit
+	beq_16 set_FAC1_zero
 
 	// Multiply signs
 	
@@ -42,29 +42,32 @@ div_FAC2_FAC1:
 	eor FAC2_sign
 	sta FAC1_sign
 
-	// Subtract the exponents    XXX what about bias?
+	// Subtract the exponents
+
+	lda #($80 + $08)                   // correction for bias and shifted mantissa
+	sta RESHO+0
+	lda #$00
+	sta RESHO+1
 
 	lda FAC2_exponent
+	jsr muldiv_RESHO_01_add_A
+
+	lda RESHO+0
 	sec
 	sbc FAC1_exponent
 	bcs !+
 
-	// Result too low, set 0 and quit
-
-	lda #$00
-
-div_FAC2_FAC1_setexp_quit:
-
-	sta FAC1_exponent
-	rts
-
+	lda RESHO+1
+	sbc #$00
+	bcc_16 set_FAC1_zero               // result too low, set 0 and quit
 !:
-	adc #$07                           // add 8, as the carry is set here
-	bcs_16 set_FAC1_max                // overflow
-	sta FAC1_exponent
+	lda RESHO+1
+	bcc_16 set_FAC1_max                // overflow
 
 	// Divide the mantissas
 
+	jsr muldiv_RESHO_set_0
+
 	// XXX
 
 
@@ -74,87 +77,5 @@ div_FAC2_FAC1_setexp_quit:
 
 
 
-// XXX adapt, move this to a separate file
-
-// Unsigned integer 32-bit division, based on code by Verz
-// divident: FAC2_mantissa, divisor: FAC1_mantissa, result: FAC2_mantissa, remainder: RESHO
-// temporary storage: INDEX+1, INDEX+2, INDEX+3
-//
-// https://codebase64.org/doku.php?id=base:24bit_division_24-bit_result
-
-// XXX test this, optimize (for temporary storage use .Y, .Z and RESHO+4)
-
-div_mantissas:
-
-	// Preset remainder to 0
-	// XXX should be common with multiplication
-
-	lda #$00
-	sta RESHO+0
-	sta RESHO+1
-	sta RESHO+2
-	sta RESHO+3
-
-	ldx #$32                           // repeat for each bit
-
-	// FALLTROUGH
-
-div_mantissas_loop:
-
-	// Multiply divident by 2, msb -> Carry
-
-	asl FAC2_mantissa+3
-	rol FAC2_mantissa+2	
-	rol FAC2_mantissa+1
-	rol FAC2_mantissa+0
-	
-	// Multiply remainder by 2, lsb <- Carry
-
-	rol RESHO+3
-	rol RESHO+2
-	rol RESHO+1
-	rol RESHO+0
-
-	// Subtract divisor to see if it fits in
-
-	lda RESHO+3
-	sec
-	sbc FAC1_mantissa+2
-	sta INDEX+3
-	
-	lda RESHO+2
-	sbc FAC1_mantissa+2
-	sta INDEX+2
-
-	lda RESHO+1
-	sbc FAC1_mantissa+1
-	sta INDEX+1
-
-	lda RESHO+0
-	sbc FAC1_mantissa+0
-	bcc div_mantissas_skip             // if Carry is not set then divisor did not fit in yet
-
-	sta RESHO+0                        // else save substraction result as new remainder,
-	lda INDEX+1
-	sta RESHO+1
-	lda INDEX+2
-	sta RESHO+2
-	lda INDEX+3
-	sta RESHO+3
-
-	inc FAC2_mantissa+3                // and INCrement result cause divisor fit in 1 times
-
-	// FALLTROUGH
-
-div_mantissas_skip:
-
-	dex
-	bne div_mantissas_loop
-
-	rts
-
-
-
-
-
 
+// XXX use 8-bit divide from here: https://codebase64.org/doku.php?id=base:8bit_divide_8bit_product