New C++ compiler with inline assembly support

[Agner Fog <agner@agner.org>]

Intel have just released version 9.0 of their C++ compiler with better 
support for inline assembly.
It can compile for the following platforms
- Linux x86 32 bit
- Linux x86 64 bit
- Linux ia64 (Itanium)
- Windows x86 32 bit
- Windows x86 64 bit
- Windows ia64 (Itanium)
I haven't tested it on FreeBSD yet, but I assume that it works on 32 and 
64 bit FreeBSD as well.

In Linux, you now have the choice between MASM syntax and AT&T syntax 
for inline assembly. MASM syntax is almost the same as NASM. If you 
choose MASM syntax, you can use the same C++ file with inline assembly 
in both Linux and Windows. It can even translate MASM syntax assembly to 
AT&T syntax, and this more reliably than any other translation tools I 
have seen yet.

To use MASM syntax under Linux, simply use the command line option  
-use-msasm

Example:

int addnumbers (int a, int b) {
   return a+b;}

Same with inline assembly in MASM syntax:

int addnumbers (int a, int b) {
   __asm {
      mov eax, a
      add eax, b
   }
}

This will work in both Linux and Windows, 32 and 64 bit. So you can use 
the same C++/asm file on all platforms. It takes care of the differences 
in calling conventions between the different platforms, and it 
automatically pushes and pops any non-volatile registers that you use in 
your code. This makes Linux assembly much easier! You can make the most 
of your program in C++ and make the critical innermost loop with inline 
assembly.

In 64-bit Linux, function parameters are transferred in registers rdi, 
rsi, rdx, rcx, r8, r9, xmm0-xmm7. If you know this, you can optimize the 
above example:

int addnumbers (int a, int b) {
   __asm {
      lea eax, [rdi+rsi]
   }
}

But then your code is no longer platform independent, of course.

The C++ compiler for Linux is available for free for noncommercial 
users. Download it from http://www.intel.com/software/products/noncom/
The C++ compiler for Windows is available with a time limited free 
evaluation license from 
https://registrationcenter.intel.com/EvalCenter/EvalForm.aspx?ProductID=411

Agner Fog
www.agner.org/assem