The %use
directive (see
section 4.6.4) includes one of
the standard macro packages included with the NASM distribution and
compiled into the NASM binary. It operates like the %include
directive (see section 4.6.1),
but the included contents is provided by NASM itself.
The names of standard macro packages are case insensitive and can be quoted or not.
As of version 2.15, NASM has %ifusable
and
%ifusing
directives to help the user understand whether an
individual package available in this version of NASM
(%ifusable
) or a particular package already loaded
(%ifusing
).
altreg
: Alternate Register NamesThe altreg
standard macro package provides alternate
register names. It provides numeric register names for all registers (not
just R8
–R15
), the Intel-defined aliases
R8L
–R15L
for the low bytes of register (as
opposed to the NASM/AMD standard names
R8B
–R15B
), and the names
R0H
–R3H
(by analogy with
R0L
–R3L
) for AH
,
CH
, DH
, and BH
.
Example use:
%use altreg proc: mov r0l,r3h ; mov al,bh ret
See also section 12.1.
smartalign
: Smart ALIGN
MacroThe smartalign
standard macro package provides for an
ALIGN
macro which is more powerful than the default (and
backwards-compatible) one (see
section 5.10.1). When the
smartalign
package is enabled, when ALIGN
is used
without a second argument, NASM will generate a sequence of instructions
more efficient than a series of NOP
. Furthermore, if the
padding exceeds a specific threshold, then NASM will generate a jump over
the entire padding sequence.
The specific instructions generated can be controlled with the new
ALIGNMODE
macro. This macro takes two parameters: one mode,
and an optional jump threshold override. If (for any reason) you need to
turn off the jump completely just set jump threshold value to –1 (or
set it to nojmp
). The following modes are possible:
generic
: Works on all x86 CPUs and should have reasonable
performance. The default jump threshold is 8. This is the default.
nop
: Pad out with NOP
instructions. The only
difference compared to the standard ALIGN
macro is that NASM
can still jump over a large padding area. The default jump threshold is 16.
k7
: Optimize for the AMD K7 (Athlon/Althon XP). These
instructions should still work on all x86 CPUs. The default jump threshold
is 16.
k8
: Optimize for the AMD K8 (Opteron/Althon 64). These
instructions should still work on all x86 CPUs. The default jump threshold
is 16.
p6
: Optimize for Intel CPUs. This uses the long
NOP
instructions first introduced in Pentium Pro. This is
incompatible with all CPUs of family 5 or lower, as well as some VIA CPUs
and several virtualization solutions. The default jump threshold is 16.
The macro __?ALIGNMODE?__
is defined to contain the current
alignment mode. A number of other macros beginning with
__?ALIGN_
are used internally by this macro package.
fp
: Floating-point macrosThis packages contains the following floating-point convenience macros:
%define Inf __?Infinity?__ %define NaN __?QNaN?__ %define QNaN __?QNaN?__ %define SNaN __?SNaN?__ %define float8(x) __?float8?__(x) %define float16(x) __?float16?__(x) %define float32(x) __?float32?__(x) %define float64(x) __?float64?__(x) %define float80m(x) __?float80m?__(x) %define float80e(x) __?float80e?__(x) %define float128l(x) __?float128l?__(x) %define float128h(x) __?float128h?__(x)
ifunc
: Integer functionsThis package contains a set of macros which implement integer functions. These are actually implemented as special operators, but are most conveniently accessed via this macro package.
The macros provided are:
These functions calculate the integer logarithm base 2 of their argument, considered as an unsigned integer. The only differences between the functions is their respective behavior if the argument provided is not a power of two.
The function ilog2e()
(alias ilog2()
)
generates an error if the argument is not a power of two.
The function ilog2f()
rounds the argument down to the
nearest power of two; if the argument is zero it returns zero.
The function ilog2c()
rounds the argument up to the nearest
power of two.
The functions ilog2fw()
(alias ilog2w()
) and
ilog2cw()
generate a warning if the argument is not a power of
two, but otherwise behaves like ilog2f()
and
ilog2c()
, respectively.
masm
: MASM compatibilitySince version 2.15, NASM has a MASM compatibility package with minimal functionality, as intended to be used primarily with machine-generated code. It does not include any "programmer-friendly" shortcuts, nor does it in any way support ASSUME, symbol typing, or MASM-style structures.
Currently, the MASM compatibility package emulates only the PTR keyword and recognize syntax displacement[index] for memory operations. To enable the package, use the directive:
%use masm
In addition, NASM now natively supports the MASM ?
and
DUP
syntax for the DB
etc data declaration
directives, regardless of if this package is included or not. See
section 3.2.1.