43 lines
1.1 KiB
NASM
43 lines
1.1 KiB
NASM
bits 64
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SECTION .data
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; empty
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SECTION .text
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global _start
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_start:
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%include "header.asm.inc"
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; multiplication: 2 * 0xFFFFFFFF
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mov eax, 2 ; 2
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mov edx, 0xFFFFFFFF ; (2^32)-1
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mul edx ; edx:eax = eax * edx
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; edx becomes 0x1 (LSB is 1)
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; eax becomes 0xFFFFFFFE (LSB is 0)
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; caveat: EDX is cleared even if even multiplaction
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; does not require it
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; e.g., multiply 2 * 4
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mov edx, 0x11223344 ; init with random value
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mov eax, 2 ; 2 (first factor, implicit)
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mov ebx, 4 ; 4 (second factor, explicit)
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mul ebx ; eax = 8, edx = 0
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; multiplication with signed integers
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mov bl, -3 ; -3 or 0xFD
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mov al, -2 ; -2 or 0xFE
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mul bl ; dl:al = bl * al (unsigned)
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mov al, -2 ; -2 or 0xFE
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imul bl ; dl:al = bl * al (signed)
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; challenge: (2^32)-1 * 2^8
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mov eax, 0xffffffff
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mov edx, 0x100
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mul edx
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%include "sysexit.asm.inc"
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