-m options are defined for the DEC Alpha implementations:
-msoft-floatis specified, functions in
libgcc.awill be used to perform floating-point operations. Unless they are replaced by routines that emulate the floating-point operations, or compiled in such a way as to call such emulations routines, these routines will issue floating-point operations. If you are compiling for an Alpha without floating-point operations, you must ensure that the library is built so as not to call them.
Note that Alpha implementations without floating-point operations are
required to have floating-point registers.
-msoft-float. If the floating-point register set is not used, floating point operands are passed in integer registers as if they were integers and floating-point results are passed in
$f0. This is a non-standard calling sequence, so any function with a floating-point argument or return value called by code compiled with
-mno-fp-regsmust also be compiled with that option.
A typical use of this option is building a kernel that does not use,
and hence need not save and restore, any floating-point registers.
_IEEE_FPis defined during compilation. The resulting code is less efficient but is able to correctly support denormalized numbers and exceptional IEEE values such as not-a-number and plus/minus infinity. Other Alpha compilers call this option
-mieeeexcept the generated code also maintains the IEEE inexact-flag. Turning on this option causes the generated code to implement fully-compliant IEEE math. In addition to
_IEEE_FP_EXACTis defined as a preprocessor macro. On some Alpha implementations the resulting code may execute significantly slower than the code generated by default. Since there is very little code that depends on the inexact-flag, you should normally not specify this option. Other Alpha compilers call this option
. The trap mode can be set to one of four values:
n, underflow traps are enabled as well.
su, but the instructions are marked to be safe for software completion (see Alpha architecture manual for details).
su, but inexact traps are enabled as well.
. The rounding-mode can be one of:
dcorresponds to round towards plus infinity.
Other Alpha compilers provide the equivalent options called
-mfp-trap-mode=sui. Its only effect is to emit the line
.eflag 48in the function prologue of the generated assembly file. Under DEC Unix, this has the effect that IEEE-conformant math library routines will be linked in.
Use this option to require GCC to construct all integer constants using code, even if it takes more instructions (the maximum is six).
You would typically use this option to build a shared library dynamic
loader. Itself a shared library, it must relocate itself in memory
before it can find the variables and constants in its own data segment.
-malpha-as) or by the GNU assembler
-mcpu=option or that of the CPU on which GCC was built if none was specified.
-mexplicit-relocsis in effect, static data is accessed via gp-relative relocations. When
-msmall-datais used, objects 8 bytes long or smaller are placed in a small data area (the
.sbsssections) and are accessed via 16-bit relocations off of the
$gpregister. This limits the size of the small data area to 64KB, but allows the variables to be directly accessed via a single instruction.
The default is
-mlarge-data. With this option the data area
is limited to just below 2GB. Programs that require more than 2GB of
data must use
mmap to allocate the data in the
heap instead of in the program's data segment.
When generating code for shared libraries,
-msmall-textis used, the compiler assumes that the code of the entire program (or shared library) fits in 4MB, and is thus reachable with a branch instruction. When
-msmall-datais used, the compiler can assume that all local symbols share the same
$gpvalue, and thus reduce the number of instructions required for a function call from 4 to 1.
The default is
EVstyle name or the corresponding chip number. GCC supports scheduling parameters for the EV4, EV5 and EV6 family of processors and will choose the default values for the instruction set from the processor you specify. If you do not specify a processor type, GCC will default to the processor on which the compiler was built.
Supported values for cpu_type are
Valid options for time are