as: AArch64 Directives
9.1.5 AArch64 Machine Directives
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'.arch NAME'
Select the target architecture. Valid values for NAME are the same
as for the '-march' command-line option.
Specifying '.arch' clears any previously selected architecture
extensions.
'.arch_extension NAME'
Add or remove an architecture extension to the target architecture.
Valid values for NAME are the same as those accepted as
architectural extensions by the '-mcpu' command-line option.
'.arch_extension' may be used multiple times to add or remove
extensions incrementally to the architecture being compiled for.
'.bss'
This directive switches to the '.bss' section.
'.cpu NAME'
Set the target processor. Valid values for NAME are the same as
those accepted by the '-mcpu=' command-line option.
'.dword EXPRESSIONS'
The '.dword' directive produces 64 bit values.
'.even'
The '.even' directive aligns the output on the next even byte
boundary.
'.inst EXPRESSIONS'
Inserts the expressions into the output as if they were
instructions, rather than data.
'.ltorg'
This directive causes the current contents of the literal pool to
be dumped into the current section (which is assumed to be the
.text section) at the current location (aligned to a word
boundary). GAS maintains a separate literal pool for each section
and each sub-section. The '.ltorg' directive will only affect the
literal pool of the current section and sub-section. At the end of
assembly all remaining, un-empty literal pools will automatically
be dumped.
Note - older versions of GAS would dump the current literal pool
any time a section change occurred. This is no longer done, since
it prevents accurate control of the placement of literal pools.
'.pool'
This is a synonym for .ltorg.
'NAME .req REGISTER NAME'
This creates an alias for REGISTER NAME called NAME. For example:
foo .req w0
ip0, ip1, lr and fp are automatically defined to alias to X16, X17,
X30 and X29 respectively.
'.tlsdescadd'
Emits a TLSDESC_ADD reloc on the next instruction.
'.tlsdesccall'
Emits a TLSDESC_CALL reloc on the next instruction.
'.tlsdescldr'
Emits a TLSDESC_LDR reloc on the next instruction.
'.unreq ALIAS-NAME'
This undefines a register alias which was previously defined using
the 'req' directive. For example:
foo .req w0
.unreq foo
An error occurs if the name is undefined. Note - this pseudo op
can be used to delete builtin in register name aliases (eg 'w0').
This should only be done if it is really necessary.
'.variant_pcs SYMBOL'
This directive marks SYMBOL referencing a function that may follow
a variant procedure call standard with different register usage
convention from the base procedure call standard.
'.xword EXPRESSIONS'
The '.xword' directive produces 64 bit values. This is the same as
the '.dword' directive.
'.cfi_b_key_frame'
The '.cfi_b_key_frame' directive inserts a 'B' character into the
CIE corresponding to the current frame's FDE, meaning that its
return address has been signed with the B-key. If two frames are
signed with differing keys then they will not share the same CIE.
This information is intended to be used by the stack unwinder in
order to properly authenticate return addresses.
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