338 lines
10 KiB
NASM
338 lines
10 KiB
NASM
title "Multiply and Divide"
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;++
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;
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; Copyright (c) 1991 Microsoft Corporation
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;
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; Module Name:
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;
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; muldiv.asm (taken from base\client\i386\critsect.asm)
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;
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; Abstract:
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;
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; Optimized multiply and divide routines
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;
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; Author:
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;
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; Bryan M. Willman (bryanwi) 2-Oct-91
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;
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; Environment:
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;
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; Any mode.
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;
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;
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;--
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.486p
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.xlist
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include ks386.inc
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include callconv.inc
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.list
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_TEXT SEGMENT PARA PUBLIC 'CODE'
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ASSUME DS:FLAT, ES:FLAT, SS:NOTHING, FS:NOTHING, GS:NOTHING
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page , 132
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subttl "Multiply and Divide"
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;++
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;
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; LONG
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; MulDiv(
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; IN LONG nNumber,
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; IN LONG nNumerator,
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; IN LONG nDenominator
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; )
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;
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; Routine Description:
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;
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; This function multiples two 32-bit numbers forming a 64-bit product.
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; The 64-bit product is rounded and then divided by a 32-bit divisor
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; yielding a 32-bit result.
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;
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; Arguments:
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;
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; nNumber - Supllies the multiplier.
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;
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; nNumerator - Supplies the multiplicand.
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;
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; nDenominator - Supplies the divisor.
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;
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; Return Value:
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;
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; If the divisor is zero or an overflow occurs, then a value of -1 is
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; returned as the function value. Otherwise, the rounded quotient is
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; returned as the funtion value.
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;
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;--
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nNumber equ [esp + 4]
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nNumerator equ [esp + 8]
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nDenominator equ DWORD PTR [esp + 12]
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cPublicProc _MulDiv, 3
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cPublicFpo 3,0
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mov eax, nNumber ; get multiplier absolute value
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or eax, eax ;
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js short MD32_First ; if s, multiplier is negative
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;
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; The multiplier is positive.
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;
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mov edx, nNumerator ; get multiplicand absolute value
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or edx, edx ;
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js MD32_Second ; if s, multiplicand is negative
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;
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; The multiplicand is positive.
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;
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mul edx ; compute 64-bit product
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mov ecx, nDenominator ; get denominator absolute value
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or ecx, ecx ;
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js MD32_Third ; if s, divisor is negative
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;
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; The divisor is positive.
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;
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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cmp edx, nDenominator ; check for overflow
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jae short MD32_error ; if ae, overflow or divide by 0
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div nDenominator ; compute quotient
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;
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; The result is postive.
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;
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or eax, eax ; check for overflow
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js short MD32_error ; if s, overlfow has occured
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stdRET _MulDiv
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MD32_error:
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xor eax, eax ; set return value to - 1
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dec eax ;
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stdRET _MulDiv
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;
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; The multiplier is negative.
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;
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MD32_First: ;
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neg eax ; negate multiplier
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mov edx, nNumerator ; get multiplicand absolute value
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or edx, edx ;
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js short MD32_First10 ; if s, multiplicand is negative
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;
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; The multiplicand is positive.
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;
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mul edx ; compute 64-bit product
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mov ecx, nDenominator ; get denominator absolute value
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or ecx, ecx ;
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js short MD32_First20 ; if s, divisor is negative
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;
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; The divisor is positive.
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;
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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cmp edx, nDenominator ; check for overflow
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jae short MD32_error10 ; if ae, overflow or divide by 0
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div nDenominator ; compute quotient
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;
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; The result is negative.
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;
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neg eax ; negate result
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jg short MD32_error10 ; if g, overlfow has occured
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stdRET _MulDiv
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;
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; The multiplier is negative and the multiplicand is negative.
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;
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MD32_First10: ;
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neg edx ; negate multiplicand
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mul edx ; compute 64-bit product
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mov ecx, nDenominator ; get denominator absolute value
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or ecx, ecx ;
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js short MD32_First30 ; if s, divisor is negative
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;
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; The divisor is positive.
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;
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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cmp edx, nDenominator ; check for overflow
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jae short MD32_error10 ; if ae, overflow or divide by 0
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div nDenominator ; compute quotient
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;
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; The result is positive.
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;
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or eax, eax ; check for overflow
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js short MD32_error10 ; if s, overlfow has occured
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stdRET _MulDiv
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MD32_error10: ;
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xor eax, eax ; set return value to - 1
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dec eax ;
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stdRET _MulDiv
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;
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; The multiplier is negative, the multiplicand is positive, and the
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; divisor is negative.
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;
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MD32_First20: ;
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neg ecx ; negate divisor
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push ecx ; save absolute value of divisor
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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pop ecx ; restore divisor
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cmp edx, ecx ; check for overflow
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jae short MD32_error10 ; if ae, overflow or divide by 0
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div ecx ; compute quotient
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;
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; The result is postive.
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;
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or eax, eax ; check for overflow
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js short MD32_error10 ; if s, overlfow has occured
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stdRET _MulDiv
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;
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; The multiplier is negative, the multiplier is negative, and the divisor
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; is negative.
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;
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MD32_First30: ;
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neg ecx ; negate divisor
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push ecx ; save absolute value of divisor
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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pop ecx ; restore divisor
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cmp edx, ecx ; check for overflow
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jae short MD32_error10 ; if ae, overflow or divide by 0
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div ecx ; compute quotient
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;
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; The result is negative.
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;
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neg eax ; negate result
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jg short MD32_error10 ; if g, overlfow has occured
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stdRET _MulDiv
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;
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; The multiplier is positive and the multiplicand is negative.
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;
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MD32_Second: ;
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neg edx ; negate multiplicand
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mul edx ; compute 64-bit product
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mov ecx, nDenominator ; get denominator absolute value
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or ecx, ecx ;
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js short MD32_Second10 ; if s, divisor is negative
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;
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; The divisor is positive.
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;
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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cmp edx, nDenominator ; check for overflow
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jae short MD32_error20 ; if ae, overflow or divide by 0
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div nDenominator ; compute quotient
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;
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; The result is negative.
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;
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neg eax ; check for overflow
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jg short MD32_error20 ; if g, overlfow has occured
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stdRET _MulDiv
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MD32_error20: ;
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xor eax, eax ; set return value to - 1
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dec eax ;
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stdRET _MulDiv
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;
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; The multiplier is positive, the multiplicand is negative, and the divisor
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; is negative.
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;
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MD32_Second10: ;
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neg ecx ; negate divisor
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push ecx ; save absolute value of divisor
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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pop ecx ; restore divisor
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cmp edx, ecx ; check for overflow
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jae short MD32_error20 ; if ae, overflow or divide by 0
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div ecx ; compute quotient
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;
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; The result is positive.
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;
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or eax, eax ; check for overflow
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js short MD32_error10 ; if s, overlfow has occured
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stdRET _MulDiv
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;
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; The multiplier is positive, the multiplicand is positive, the divisor
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; is negative.
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;
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MD32_Third: ;
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neg ecx ; negate divisor
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push ecx ; save absolute value of divisor
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sar ecx, 1 ; compute rounding value
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add eax, ecx ; round the 64-bit produce by the
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adc edx, 0 ; divisor / 2
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pop ecx ; restore divisor
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cmp edx, ecx ; check for overflow
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jae short MD32_error20 ; if ae, overflow or divide by 0
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div ecx ; compute quotient
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;
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; The result is negative.
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;
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neg eax ; negate result
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jg short MD32_error20 ; if g, overflow has occured
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stdRET _MulDiv
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stdENDP _MulDiv
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_TEXT ends
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end
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