Update mul_FAC2_FAC1

src/basic/math/bab7.MULDIV.s

@@ -0,0 +1,47 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
+; Math package - add exponents of FAC1 and FAC2 for multiplication and division
+;
+; This is verified to be identical to the original Microsoft implementation where it was named MULDIV
+;
+
+
+	;CHECK SPECIAL CASES AND ADD EXPONENTS FOR FMULT, FDIV.
+	
+MULDIV:
+        lda FAC2_exponent   ; Exponent of FAC2 = 0?
+MLDEXP:
+        beq ZEREMV
+        clc
+        adc FAC1_exponent   ; Result is in A
+        bcc @1              ; Find CF XOR NF
+        bmi GOOVER          ; Overflow if bits match
+        clc
+        +skip_2_bytes_trash_nvz
+@1:
+        bpl ZEREMV          ; underflow
+        adc #$80            ; Add bias
+        sta FAC1_exponent
+        bne @2
+	    jmp ZEROML          ; Zero the rest of it
+@2:
+        lda ARISGN
+        sta FAC1_sign       ; ARISGN is result's sign
+        rts
+
+MLDVEX:
+        lda FAC1_sign
+        eor #$FF
+        bmi GOOVER
+ZEREMV:
+        pla                 ; Get address off stack
+        pla
+        jmp zero_FAC1       ; underflow
+GOOVER:
+        jmp overflow_error  ; overflow