Itanium® Architecture for Programmers: Understanding 64-Bit Processors and EPIC Principles

F.2. GCC Compiler for Linux

Many C compilers support an intrinsic function asm(...) to provide a general means of inserting native machine instructions directly into a program through inline assembly.

The syntax of the asm function uses a very general text-substitution scheme into which the requirements for many assembly languages can be accommodated:

asm volatile ( "pattern for machine instruction(s)"
: list of outputs
: list of inputs
: list of indirectly modified items );

where volatile is optional but may inhibit some compilers from deleting, moving appreciably, or combining the machine instructions; where instructions can be separated with \n\t; and where __asm__ is an alternate keyword for ISO C compatibility.

Output or input parameters ...