inline-assembly - w3toppers.com

Using base pointer register in C++ inline asm

What is the difference between ‘asm’, ‘asm’ and ‘asm__’?

There’s a massive difference between MSVC inline asm and GNU C inline asm. GCC syntax is designed for optimal output without wasted instructions, for wrapping a single instruction or something. MSVC syntax is designed to be fairly simple, but AFAICT it’s impossible to use without the latency and extra instructions of a round trip through … Read more

How can I indicate that the memory pointed to by an inline ASM argument may be used?

That’s correct; asking for a pointer as input to inline asm does not imply that the pointed-to memory is also an input or output or both. With a register input and register output, for all gcc knows your asm just aligns a pointer by masking off the low bits, or adds a constant to it. … Read more