Examples of Pseudo-Operations

B

This chapter shows some examples of ways to use various pseudo-ops.

Example 1

This example shows how to use the following pseudo-ops to specify the bindings of variables in C:

common, .global, .local, .weak

The following C definitions/declarations for example:

int foo1 = 1; #pragma weak foo2 = foo1 static int foo3; static int foo4 = 2;

can be translated into the following assembly code:

.pushsection ".data" .global foo1 ! int foo1 = 1 .align 4

foo1: .word 0x1 .type foo1,#object ! foo1 is of type data object, .size foo1,4 ! with size = 4 bytes .weak foo2 ! #pragma weak foo2 = foo1 foo2 = foo1 .local foo3 ! static int foo3 .common foo3,4,4 .align 4 ! static int foo4 = 2 foo4: .word 0x2 .type foo4,#object .size foo4,4 .popsection

Example 2

This example illustrates how to use the pseudo-op .ident to generate a string in the .comment section of the object file for identification purposes.

.ident"acomp: (CDS) SPARCompilers 2.0 alpha4 12 Aug 1991"

Example 3

The pseudo-ops illustrated in this example are .align, .global, .type, and .size.

The following C subroutine for example:

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

can be translated into the following assembly code:

.section ".text" .global sum .align 4 sum: retl add %o0,%o1,%o0 ! (a + b) is done in the ! delay slot of retl .type sum,#function ! sum is of type function .size sum,.-sum ! size of sum is the diff ! of current location ! counter and the initial ! definition of sum

Example 4

The pseudo-ops illustrated in this example are .section, .ascii, and .align. The example calls the printf function to output the string "hello world".

.section ".data1" .align 4 .L16: .ascii "hello world\n\0" .section ".text" .global main main: save %sp,-96,%sp set .L16,%o0 call printf,1 nop restore

Example 5

This example illustrates how to use the .volatile and .nonvolatile pseudo-ops to protect a section of handwritten asembly code from peephole optimization.

.volatile t 0x24 std %g2, [%o0] retl nop .nonvolatile