adding a carry

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FoXx

Joined: 25 Feb 2025
Posts: 20

FoXx 06 Oct 2025, 10:25

Code:

SCALE_SIZE = 1024
VOLUME = 100000

struct FLOAT64

        high    dd ?
        low     dd ?
        under   dd ?
ends


        mov ESI, [lpSinusScale]
        mov EBX, VOLUME
        mov ECX, SCALE_SIZE

        mov EDI, val
        xor EAX, EAX
        stosd
        stosd
        stosd

.integrator:
        lodsd
        mul EBX
        add [val.under],EAX
        adс [val.low],  EDX
        adc [val.high], 0

        loop .integrator

I'm trying to integrate a 64-bit value into a 32-bit processor. Precise calculations are required. A solution already exists. I'm not very familiar with x86 instructions.
Is there a way to add a carry without adding a third value?

Code:

        add [val.under],EAX
        adс [val.low],  EDX
        adz [val.high]          ;       similar

Last edited by FoXx on 06 Oct 2025, 13:37; edited 1 time in total

06 Oct 2025, 10:25

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20739
Location: In your JS exploiting you and your system

revolution 06 Oct 2025, 11:21

Ideally the code should propagate the carry through all variables.

Code:

        add [val.under],EAX
        adc [val.low],  EDX ; use ADC here
        adc [val.high], 0   ; use ADC here also

06 Oct 2025, 11:21

FoXx

Joined: 25 Feb 2025
Posts: 20

FoXx 06 Oct 2025, 13:37

You're right. It's figurative code. The order of the operators is wrong. I've fixed it.

Is there such an instruction for the х86 processor?

06 Oct 2025, 13:37

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20739
Location: In your JS exploiting you and your system

revolution 06 Oct 2025, 21:12

There is no opcode ADZ.

06 Oct 2025, 21:12

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