What does xchg rax rax do?

What does xchg rax rax do?

“xchg rax,rax” is a collection of assembly gems and riddles I found over many years of reversing and writing assembly code. The book contains 0x40 short assembly snippets, each built to teach you one concept about assembly, math or life in general.

What is RAX Assembly?

rax is the 64-bit, “long” size register. It was added in 2003 during the transition to 64-bit processors. eax is the 32-bit, “int” size register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU.

What is Xchg instruction?

In 8085 Instruction set, there is one mnemonic XCHG, which stands for eXCHanGe. This is an instruction to exchange contents of HL register pair with DE register pair. This instruction uses implied addressing mode. As it is1-Byte instruction, so It occupies only 1-Byte in the memory.

What is XADD?

DESCRIPTION: The XADD instruction adds the source to the destination and stores the sum in the destination, as with any addition. The difference is that after the addition takes place, the original value of the destination is copied into source operand.

What does CLTQ do in assembly?

The cltq instruction is a specialized movs that operates on %rax . This no-operand instruction does sign-extension in-place on %rax ; source bitwidth is l, destination bitwidth is q. cltq # operates on %rax, sign-extend 4-byte src to 8-byte dst, shorthand for movslq %eax,%rax.

What does MOVQ do in assembly?

The movq instruction moves the 1st argument (passed in %rdi) to its place on the stack. The argument occupies the first stack position (stack entries are 8 bytes) after the base pointer (%rbp). 0(%rbp) stores the previous frame’s base pointer.

Which command do you use to add a value to a Redis stream named my stream?

Because Streams are an append only data structure, the fundamental write command, called XADD, appends a new entry into the specified stream.

What does CLTQ mean?

Convert Long To Quad
The mnemonics are: Convert Long To Quad ( cltq ): AT-style.

What means EAX?

It stands for a general purpose register. The 16 bit AX register can be addressed as AH (high byte) and AL (low byte). The EAX register is the 32 bit version of the AX register. The E stands for extended.

Who is the author of XCHG Rax, Rax?

In words of xorpd, the author of xchg rax,rax: xchg rax,rax is a collection of assembly gems and riddles I found over many years of reversing and writing assembly code. The book contains 0x40 short assembly snippets, each built to teach you one concept about assembly, math or life in general. Be warned – This book is not for beginners.

Is there a Boolean cast for Rax in XCHG?

Boolean cast: rax := bool (rax), i.e. rax := rax ? 1 : 0. Minimum function: rax := min (rax, rdx). Replaces uppercase with lowercase characters and vice-versa. Allows to branch depending on whether rax is in range [5,9] using only one jbe jump. Does nothing since the instructions cancel each other.

Why does Rax end up with the same value as RCX?

Registers rax, rcx end up with the same value, thanks to distributivity of ROR (with XOR). Registers rdx, rbx end up with the same value, thanks to distributivity of AND (with XOR) and commutativity of XOR. Registers rax, rcx end up with the same value, thanks to DeMorgan’s law.

Which is XCHG instruction exchanges two operands with itself?

The title, xchg rax, rax, is a NOP instruction (pronounced no-op, for no operation): xchg exchanges the data of two operands, in this case of rax with itself. The author’s name, xorpd, is a bitwise logical XOR (exclusive or) of packed double-precision floating-point values. The xor logical operation is one of my favorites.