assembly

问题 I need to calculate the parity of a 32 bits number and return it. To do this I must use XOR, SHR,SETP(or similar) and movzx. Somebody have an idea ? 回答1: Many ways to do this, of course. If you decide to use the hardware parity flag, keep in mind that it only checks the low 8 bits. A solution using this approach might be to process your 32 bit input as four 8 bit values, and use XOR on the partial results: p(31:0) = p(31:24) ^ p(23:16) ^ p(15:8) ^ p(7:0) To get the 8 bit units, you can use

问题 My assignment is to write a program that calculates first seven values of fibonacci number sequence. the formula given is: Fib(1) = 1, Fib(2) = 1, Fib(n) = Fib(n-1) + Fib(n-2) I believe that is a function but I do not understand how to incorporate it into code. I need to place the values in EAX register. I am using MASM not that makes any difference. Any hints? 回答1: I suspect that this is an academic assignment so I'm only going to partially answer the question. The fibonacci sequence is

问题 I've been given an assingment to make a calculator in 8086 assembly that will add, substract, multiply and divide big decimal numbers. These numbers can be 30 digits long at most. I've used 3 arrays to house these numbers (num1, num2, result). I'm stuck at the addition, because every time I run the program, it displays that the result array is empty (it shows a plus sign and 60 zeroes) can you tell what is wrong with my code? ADDER: MOV BP, offset num1 MOV SI, offset num2 MOV DI, offset

问题 I’m trying to write a minimal loop around pcmpestri in x86-64 asm (actually in-line asm embedded in Dlang using the GDC compiler). There are a couple of things that I don’t understand I you are using pcmpestri with two pointers to strings, are the lengths of the strings in rax and rdx ? If so, what are the units? count in bytes always, or count in chars where 1 count = 2 bytes for uwords ? Does pcmpestri check for short strings? ie len str1 or str2 < 16 bytes or 8 uwords if uwords Does

问题 This question already has answers here : Handling calls to (potentially) far away ahead-of-time compiled functions from JITed code (1 answer) How to execute a call instruction with a 64-bit absolute address? (1 answer) Call an absolute pointer in x86 machine code (2 answers) Closed 8 months ago . I am trying to hook a function in a process that is 64 bit, the relative jump is over 4 bytes so I can't do it via normal methods. Is there any way to jump 8 bytes relative or absolute? Cheers if any

问题 This question already has answers here : Handling calls to (potentially) far away ahead-of-time compiled functions from JITed code (1 answer) How to execute a call instruction with a 64-bit absolute address? (1 answer) Call an absolute pointer in x86 machine code (2 answers) Closed 8 months ago . I am trying to hook a function in a process that is 64 bit, the relative jump is over 4 bytes so I can't do it via normal methods. Is there any way to jump 8 bytes relative or absolute? Cheers if any

问题 Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 2 years ago . Improve this question I am looking to write a program that will need to do low level work with processes (ie. using the fork system call, among others). This program is to be written in C++ and is to run only on Linux. Ideally, it will be portable across CPU architectures (ie. x86, x86

问题 Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 2 years ago . Improve this question I am looking to write a program that will need to do low level work with processes (ie. using the fork system call, among others). This program is to be written in C++ and is to run only on Linux. Ideally, it will be portable across CPU architectures (ie. x86, x86

问题 I was benchmarking some counting in a loop code. g++ was used with -O2 code and I noticed that it has some perf problems when some condition is true in 50% of the cases. I assumed that may mean that code does unnecessary jumps(since clang produces faster code so it is not some fundamental limitation). What I find in this asm output funny is that code jumps over one simple add. => 0x42b46b <benchmark_many_ints()+1659>: movslq (%rdx),%rax 0x42b46e <benchmark_many_ints()+1662>: mov %rax,%rcx

问题 I was benchmarking some counting in a loop code. g++ was used with -O2 code and I noticed that it has some perf problems when some condition is true in 50% of the cases. I assumed that may mean that code does unnecessary jumps(since clang produces faster code so it is not some fundamental limitation). What I find in this asm output funny is that code jumps over one simple add. => 0x42b46b <benchmark_many_ints()+1659>: movslq (%rdx),%rax 0x42b46e <benchmark_many_ints()+1662>: mov %rax,%rcx