компилятор C и C ++ проекта GNU (GNU project C and C++ compiler)
Параметры подробно (Options detail)
Nios II
These are the options defined for the Altera Nios II processor.
-G num
Put global and static objects less than or equal to num bytes
into the small data or BSS sections instead of the normal
data or BSS sections. The default value of num is 8.
-mgpopt=option
-mgpopt
-mno-gpopt
Generate (do not generate) GP-relative accesses. The
following option names are recognized:
none
Do not generate GP-relative accesses.
local
Generate GP-relative accesses for small data objects that
are not external, weak, or uninitialized common symbols.
Also use GP-relative addressing for objects that have
been explicitly placed in a small data section via a
"section" attribute.
global
As for local, but also generate GP-relative accesses for
small data objects that are external, weak, or common.
If you use this option, you must ensure that all parts of
your program (including libraries) are compiled with the
same -G setting.
data
Generate GP-relative accesses for all data objects in the
program. If you use this option, the entire data and BSS
segments of your program must fit in 64K of memory and
you must use an appropriate linker script to allocate
them within the addressable range of the global pointer.
all Generate GP-relative addresses for function pointers as
well as data pointers. If you use this option, the
entire text, data, and BSS segments of your program must
fit in 64K of memory and you must use an appropriate
linker script to allocate them within the addressable
range of the global pointer.
-mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is
equivalent to -mgpopt=none.
The default is -mgpopt except when -fpic or -fPIC is
specified to generate position-independent code. Note that
the Nios II ABI does not permit GP-relative accesses from
shared libraries.
You may need to specify -mno-gpopt explicitly when building
programs that include large amounts of small data, including
large GOT data sections. In this case, the 16-bit offset for
GP-relative addressing may not be large enough to allow
access to the entire small data section.
-mgprel-sec=regexp
This option specifies additional section names that can be
accessed via GP-relative addressing. It is most useful in
conjunction with "section" attributes on variable
declarations and a custom linker script. The regexp is a
POSIX Extended Regular Expression.
This option does not affect the behavior of the -G option,
and the specified sections are in addition to the standard
".sdata" and ".sbss" small-data sections that are recognized
by -mgpopt.
-mr0rel-sec=regexp
This option specifies names of sections that can be accessed
via a 16-bit offset from "r0"; that is, in the low 32K or
high 32K of the 32-bit address space. It is most useful in
conjunction with "section" attributes on variable
declarations and a custom linker script. The regexp is a
POSIX Extended Regular Expression.
In contrast to the use of GP-relative addressing for small
data, zero-based addressing is never generated by default and
there are no conventional section names used in standard
linker scripts for sections in the low or high areas of
memory.
-mel
-meb
Generate little-endian (default) or big-endian (experimental)
code, respectively.
-march=arch
This specifies the name of the target Nios II architecture.
GCC uses this name to determine what kind of instructions it
can emit when generating assembly code. Permissible names
are: r1, r2.
The preprocessor macro "__nios2_arch__" is available to
programs, with value 1 or 2, indicating the targeted ISA
level.
-mbypass-cache
-mno-bypass-cache
Force all load and store instructions to always bypass cache
by using I/O variants of the instructions. The default is not
to bypass the cache.
-mno-cache-volatile
-mcache-volatile
Volatile memory access bypass the cache using the I/O
variants of the load and store instructions. The default is
not to bypass the cache.
-mno-fast-sw-div
-mfast-sw-div
Do not use table-based fast divide for small numbers. The
default is to use the fast divide at -O3 and above.
-mno-hw-mul
-mhw-mul
-mno-hw-mulx
-mhw-mulx
-mno-hw-div
-mhw-div
Enable or disable emitting "mul", "mulx" and "div" family of
instructions by the compiler. The default is to emit "mul"
and not emit "div" and "mulx".
-mbmx
-mno-bmx
-mcdx
-mno-cdx
Enable or disable generation of Nios II R2 BMX (bit
manipulation) and CDX (code density) instructions. Enabling
these instructions also requires -march=r2. Since these
instructions are optional extensions to the R2 architecture,
the default is not to emit them.
-mcustom-insn=N
-mno-custom-insn
Each -mcustom-insn=N option enables use of a custom
instruction with encoding N when generating code that uses
insn. For example, -mcustom-fadds=253 generates custom
instruction 253 for single-precision floating-point add
operations instead of the default behavior of using a library
call.
The following values of insn are supported. Except as
otherwise noted, floating-point operations are expected to be
implemented with normal IEEE 754 semantics and correspond
directly to the C operators or the equivalent GCC built-in
functions.
Single-precision floating point:
fadds, fsubs, fdivs, fmuls
Binary arithmetic operations.
fnegs
Unary negation.
fabss
Unary absolute value.
fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
Comparison operations.
fmins, fmaxs
Floating-point minimum and maximum. These instructions
are only generated if -ffinite-math-only is specified.
fsqrts
Unary square root operation.
fcoss, fsins, ftans, fatans, fexps, flogs
Floating-point trigonometric and exponential functions.
These instructions are only generated if
-funsafe-math-optimizations is also specified.
Double-precision floating point:
faddd, fsubd, fdivd, fmuld
Binary arithmetic operations.
fnegd
Unary negation.
fabsd
Unary absolute value.
fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
Comparison operations.
fmind, fmaxd
Double-precision minimum and maximum. These instructions
are only generated if -ffinite-math-only is specified.
fsqrtd
Unary square root operation.
fcosd, fsind, ftand, fatand, fexpd, flogd
Double-precision trigonometric and exponential functions.
These instructions are only generated if
-funsafe-math-optimizations is also specified.
Conversions:
fextsd
Conversion from single precision to double precision.
ftruncds
Conversion from double precision to single precision.
fixsi, fixsu, fixdi, fixdu
Conversion from floating point to signed or unsigned
integer types, with truncation towards zero.
round
Conversion from single-precision floating point to signed
integer, rounding to the nearest integer and ties away
from zero. This corresponds to the "__builtin_lroundf"
function when -fno-math-errno is used.
floatis, floatus, floatid, floatud
Conversion from signed or unsigned integer types to
floating-point types.
In addition, all of the following transfer instructions for
internal registers X and Y must be provided to use any of the
double-precision floating-point instructions. Custom
instructions taking two double-precision source operands
expect the first operand in the 64-bit register X. The other
operand (or only operand of a unary operation) is given to
the custom arithmetic instruction with the least significant
half in source register src1 and the most significant half in
src2. A custom instruction that returns a double-precision
result returns the most significant 32 bits in the
destination register and the other half in 32-bit register Y.
GCC automatically generates the necessary code sequences to
write register X and/or read register Y when double-precision
floating-point instructions are used.
fwrx
Write src1 into the least significant half of X and src2
into the most significant half of X.
fwry
Write src1 into Y.
frdxhi, frdxlo
Read the most or least (respectively) significant half of
X and store it in dest.
frdy
Read the value of Y and store it into dest.
Note that you can gain more local control over generation of
Nios II custom instructions by using the
"target("custom-insn=N")" and "target("no-custom-insn")"
function attributes or pragmas.
-mcustom-fpu-cfg=name
This option enables a predefined, named set of custom
instruction encodings (see -mcustom-insn above). Currently,
the following sets are defined:
-mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252
-mcustom-fadds=253 -mcustom-fsubs=254
-fsingle-precision-constant
-mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252
-mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255
-fsingle-precision-constant
-mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243
-mcustom-fixsi=244 -mcustom-floatis=245 -mcustom-fcmpgts=246
-mcustom-fcmples=249 -mcustom-fcmpeqs=250
-mcustom-fcmpnes=251 -mcustom-fmuls=252 -mcustom-fadds=253
-mcustom-fsubs=254 -mcustom-fdivs=255
-fsingle-precision-constant
Custom instruction assignments given by individual
-mcustom-insn= options override those given by
-mcustom-fpu-cfg=, regardless of the order of the options on
the command line.
Note that you can gain more local control over selection of a
FPU configuration by using the
"target("custom-fpu-cfg=name")" function attribute or pragma.
These additional -m options are available for the Altera Nios II
ELF (bare-metal) target:
-mhal
Link with HAL BSP. This suppresses linking with the GCC-
provided C runtime startup and termination code, and is
typically used in conjunction with -msys-crt0= to specify the
location of the alternate startup code provided by the HAL
BSP.
-msmallc
Link with a limited version of the C library, -lsmallc,
rather than Newlib.
-msys-crt0=startfile
startfile is the file name of the startfile (crt0) to use
when linking. This option is only useful in conjunction with
-mhal.
-msys-lib=systemlib
systemlib is the library name of the library that provides
low-level system calls required by the C library, e.g. "read"
and "write". This option is typically used to link with a
library provided by a HAL BSP.
