9.1.5 Alpha Assembler Directives
as for the Alpha supports many additional directives for compatibility with the native assembler. This section describes them only briefly.
- Specifies the target processor. This is equivalent to the
-mcpu command-line option. See Options,
for a list of values for cpu.
- Mark the beginning of function. An optional number may follow for
compatibility with the OSF/1 assembler, but is ignored. When generating
.mdebuginformation, this will create a procedure descriptor for the function. In ELF, it will mark the symbol as a function a-la the generic
- Mark the end of function. In ELF, it will set the size of the symbol
a-la the generic
- Indicate which of the integer registers are saved in the current
function's stack frame. mask is interpreted a bit mask in which
bit n set indicates that register n is saved. The registers
are saved in a block located offset bytes from the canonical
frame address (CFA) which is the value of the stack pointer on entry to
the function. The registers are saved sequentially, except that the
return address register (normally
$26) is saved first.
This and the other directives that describe the stack frame are currently only used when generating
.mdebuginformation. They may in the future be used to generate DWARF2
.debug_frameunwind information for hand written assembly.
- Indicate which of the floating-point registers are saved in the current
stack frame. The mask and offset parameters are interpreted
- Describes the shape of the stack frame. The frame pointer in use is
framereg; normally this is either
$sp. The frame pointer is frameoffset bytes below the CFA. The return address is initially located in retreg until it is saved as indicated in
.mask. For compatibility with OSF/1 an optional argoffset parameter is accepted and ignored. It is believed to indicate the offset from the CFA to the saved argument registers.
- Indicate that the stack frame is set up and all registers have been
spilled. The argument n indicates whether and how the function
uses the incoming procedure vector (the address of the called
$27. 0 indicates that
$27is not used; 1 indicates that the first two instructions of the function use
$27to perform a load of the GP register; 2 indicates that
$27is used in some non-standard way and so the linker cannot elide the load of the procedure vector during relaxation.
- Used to indicate the use of the
$27register, similar to
.prologue, but without the other semantics of needing to be inside an open
The which argument should be either
no, indicating that
$27is not used, or
std, indicating that the first two instructions of the function perform a GP load.
One might use this directive instead of
.prologueif you are also using dwarf2 CFI directives.
- Computes the difference between the address in expression and the
GP for the current object file, and stores it in 4 bytes. In addition
to being smaller than a full 8 byte address, this also does not require
a dynamic relocation when used in a shared library.
- Stores expression as an ieee double precision value.
- Stores expression as an ieee single precision value.
- Stores expression as a VAX F format value.
- Stores expression as a VAX G format value.
- Stores expression as a VAX D format value.
- Enables or disables various assembler features. Using the positive
name of the feature enables while using nofeature disables.
- Indicates that macro expansions may clobber the assembler
$28) register. Some macros may not be expanded without this and will generate an error message if
noatis in effect. When
atis in effect, a warning will be generated if
$atis used by the programmer.
- Enables the expansion of macro instructions. Note that variants of real
instructions, such as
br $31,labelare considered alternate forms and not macros.
- These control whether and how the assembler may re-order instructions. Accepted for compatibility with the OSF/1 assembler, but as does not do instruction scheduling, so these features are ignored.
The following directives are recognized for compatibility with the OSF/1 assembler but are ignored.
.proc .aproc .reguse .livereg .option .aent .ugen .eflag .alias .noalias