as: s390 Directives
9.40.4 Assembler Directives
---------------------------
'as' for s390 supports all of the standard ELF assembler directives as
outlined in the main part of this document. Some directives have been
extended and there are some additional directives, which are only
available for the s390 'as'.
'.insn'
This directive permits the numeric representation of an
instructions and makes the assembler insert the operands according
to one of the instructions formats for '.insn' (
s390
Formats). For example, the instruction 'l %r1,24(%r15)' could be
written as '.insn rx,0x58000000,%r1,24(%r15)'.
'.short'
'.long'
'.quad'
This directive places one or more 16-bit (.short), 32-bit (.long),
or 64-bit (.quad) values into the current section. If an ELF or
TLS modifier is used only the following expressions are allowed:
'symbol@modifier + constant', 'symbol@modifier + label + constant',
and 'symbol@modifier - label + constant'. The following modifiers
are available:
'@got'
'@got12'
The @got modifier can be used for .short, .long and .quad.
The @got12 modifier is synonym to @got. The symbol is added
to the GOT. The symbol term is replaced with offset from the
start of the GOT to the GOT slot for the symbol.
'@gotoff'
The @gotoff modifier can be used for .short, .long and .quad.
The symbol term is replaced with the offset from the start of
the GOT to the address of the symbol.
'@gotplt'
The @gotplt modifier can be used for .long and .quad. A
procedure linkage table entry is generated for the symbol and
a jump slot for the symbol is added to the GOT. The symbol
term is replaced with the offset from the start of the GOT to
the jump slot for the symbol.
'@plt'
The @plt modifier can be used for .long and .quad. A
procedure linkage table entry us generated for the symbol.
The symbol term is replaced with the address of the PLT entry
for the symbol.
'@pltoff'
The @pltoff modifier can be used for .short, .long and .quad.
The symbol term is replaced with the offset from the start of
the PLT to the address of the symbol.
'@tlsgd'
'@tlsldm'
The @tlsgd and @tlsldm modifier can be used for .long and
.quad. A tls_index structure for the symbol is added to the
GOT. The symbol term is replaced with the offset from the
start of the GOT to the tls_index structure.
'@gotntpoff'
'@indntpoff'
The @gotntpoff and @indntpoff modifier can be used for .long
and .quad. The symbol is added to the static TLS block and
the negated offset to the symbol in the static TLS block is
added to the GOT. For @gotntpoff the symbol term is replaced
with the offset from the start of the GOT to the GOT slot, for
@indntpoff the symbol term is replaced with the address of the
GOT slot.
'@dtpoff'
The @dtpoff modifier can be used for .long and .quad. The
symbol term is replaced with the offset of the symbol relative
to the start of the TLS block it is contained in.
'@ntpoff'
The @ntpoff modifier can be used for .long and .quad. The
symbol term is replaced with the offset of the symbol relative
to the TCB pointer.
For more information about the thread local storage modifiers see
the ELF extension documentation 'ELF Handling For Thread-Local
Storage'.
'.ltorg'
This directive causes the current contents of the literal pool to
be dumped to the current location (s390 Literal Pool
Entries).
'.machine STRING[+EXTENSION]...'
This directive allows changing the machine for which code is
generated. 'string' may be any of the '-march=' selection options,
or 'push', or 'pop'. '.machine push' saves the currently selected
cpu, which may be restored with '.machine pop'. Be aware that the
cpu string has to be put into double quotes in case it contains
characters not appropriate for identifiers. So you have to write
'"z9-109"' instead of just 'z9-109'. Extensions can be specified
after the cpu name, separated by plus characters. Valid extensions
are: 'htm', 'nohtm', 'vx', 'novx'. They extend the basic
instruction set with features from a higher cpu level, or remove
support for a feature from the given cpu level.
Example: 'z13+nohtm' allows all instructions of the z13 cpu except
instructions from the HTM facility.
'.machinemode string'
This directive allows to change the architecture mode for which
code is being generated. 'string' may be 'esa', 'zarch',
'zarch_nohighgprs', 'push', or 'pop'. '.machinemode
zarch_nohighgprs' can be used to prevent the 'highgprs' flag from
being set in the ELF header of the output file. This is useful in
situations where the code is gated with a runtime check which makes
sure that the code is only executed on kernels providing the
'highgprs' feature. '.machinemode push' saves the currently
selected mode, which may be restored with '.machinemode pop'.
Info Catalog
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