Is there an introduction to x64 assembly code?
For years, PC programmers used x86 assembly to write performance-critical code. However, 32-bit PCs are being replaced with 64-bit ones, and the underlying assembly code has changed. This white paper is an introduction to x64 assembly.
When do you need to use Assembly in a program?
Assembly is often used for performance-critical parts of a program, although it is difficult to outperform a good C++ compiler for most programmers. Assembly knowledge is useful for debugging code – sometimes a compiler makes incorrect assembly code and stepping through the code in a debugger helps locate the cause.
Why is it important to know assembly language?
Assembly knowledge is useful for debugging code – sometimes a compiler makes incorrect assembly code and stepping through the code in a debugger helps locate the cause. Code optimizers sometimes make mistakes. Another use for assembly is interfacing with or fixing code for which you have no source code.
What is the difference between x86 and x64?
x64 is a generic name for the 64-bit extensions to Intel’s and AMD’s 32-bit x86 instruction set architecture (ISA). AMD introduced the first version of x64, initially called x86-64 and later renamed AMD64.
What’s the difference between Itanium 64 and IA 64?
Neither is to be confused with the 64-bit Intel® Itanium® architecture, which is called IA-64. This white paper won’t cover hardware details such as caches, branch prediction, and other advanced topics. Several references will be given at the end of the article for further reading in these areas.
How are the eight 64 bit MMX registers aliased?
The eight 64-bit MMX registers MMX0-MMX7 are aliased on top of FPR0-7, which means any code mixing FP and MMX operations must be careful not to overwrite required values. The MMX instructions operate on integer types, allowing byte, word, and doubleword operations to be performed on values in the MMX registers in parallel.
How does the test instruction work in x86?
In the x86 assembly language, the TEST instruction performs a bitwise AND on two operands. The flags SF, ZF, PF are modified while the result of the AND is discarded. The OF and CF flags are set to 0, while AF flag is undefined.
How does a 64 bit instruction pointer work?
The 64-bit instruction pointer RIP points to the next instruction to be executed, and supports a 64-bit flat memory model. Memory address layout in current operating systems is covered later. The stack pointer RSP points to the last item pushed onto the stack, which grows toward lower addresses.