Yesterday I learned that inline assembly (with the __asm keyword) is not supported under Microsoft Visual C++ when compiling for AMD64 and Itanium targets.
Is that correct? And if so, does anyone know why they would not support inline assembly for those targets? It seems like a rather big feature to just drop...
Correct, it still isn't supported in VS 2010 Beta 1. My guess is that inline assembly is just too difficult to implement: the way Microsoft implemented it, it integrates with the surrounding C code so that data can flow in and out of the C code, and appropriate glue code is automatically injected. For that, the C compiler actually needs to understand the assembler code; they just haven't implemented that for AMD64 and Itanium.
It seems like a rather big feature to just drop...
It's quite easy to call a function written with an assembler, as long as you follow C conventions. This tutorial explains how.
来源：https://stackoverflow.com/questions/1295452/why-does-msvc-not-support-inline-assembly-for-amd64-and-itanium-targets