(This feature is APPLE ONLY.)
In addition to writing single statements in assembly, you can also define blocks and entire functions to use a mixed assembly and C syntax. The syntax follows that used in Metrowerks' CodeWarrior. This extension must be explicitly enabled with the -fasm-blocks.
The block syntax consists of asm followed by braces, with the
assembly instructions on separate lines. (However, ';' may be used to
put several instructions on one line.) You write labels with either a
preceding '´or a trailing ':' (or both, if you prefer); labels are
always local to the asm block, and there is no way for a label in one
block to refer to a label in another block. Comments and lexical
rules are as for standard C/C++.
int foo (int arg) {
register int bar;
asm {
li bar, 42
add bar, arg, bar ; nop ; ; nop
}
return bar;
}
The function syntax uses asm as a keyword in the function
definition. In this form, C declarations may appear at the beginning
of the function body, in order to declare variables that you want to
use in the body, but may not be used after the first assembly opcode
or label (even in C99 or C++).
asm int baz (int arg1) {
register int loc1, loc2;
@123
li loc1,4 * 89
nand. r5,arg1,loc1
ble- cr0, @123
otherlab: nop
mr r3,r5
}
Note that the compiler just passes the instructions through to the assembler with only necessary changes, such as a subsitution of globally unique labels. Assembly syntax errors will therefore be reported by the assembler.