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<title>Using the GNU Compiler Collection (GCC): Nios II Options</title>
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<a name="Nios-II-Options"></a>
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<div class="header">
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<p>
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Next: <a href="Nvidia-PTX-Options.html#Nvidia-PTX-Options" accesskey="n" rel="next">Nvidia PTX Options</a>, Previous: <a href="NDS32-Options.html#NDS32-Options" accesskey="p" rel="prev">NDS32 Options</a>, Up: <a href="Submodel-Options.html#Submodel-Options" accesskey="u" rel="up">Submodel Options</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Nios-II-Options-1"></a>
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<h4 class="subsection">3.18.32 Nios II Options</h4>
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<a name="index-Nios-II-options"></a>
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<a name="index-Altera-Nios-II-options"></a>
|
|
<p>These are the options defined for the Altera Nios II processor.
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</p>
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<dl compact="compact">
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<dt><code>-G <var>num</var></code></dt>
|
<dd><a name="index-G-2"></a>
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<a name="index-smaller-data-references-1"></a>
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<p>Put global and static objects less than or equal to <var>num</var> bytes
|
into the small data or BSS sections instead of the normal data or BSS
|
sections. The default value of <var>num</var> is 8.
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</p>
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</dd>
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<dt><code>-mgpopt=<var>option</var></code></dt>
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<dt><code>-mgpopt</code></dt>
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<dt><code>-mno-gpopt</code></dt>
|
<dd><a name="index-mgpopt-1"></a>
|
<a name="index-mno_002dgpopt-1"></a>
|
<p>Generate (do not generate) GP-relative accesses. The following
|
<var>option</var> names are recognized:
|
</p>
|
<dl compact="compact">
|
<dt>‘<samp>none</samp>’</dt>
|
<dd><p>Do not generate GP-relative accesses.
|
</p>
|
</dd>
|
<dt>‘<samp>local</samp>’</dt>
|
<dd><p>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 <code>section</code>
|
attribute.
|
</p>
|
</dd>
|
<dt>‘<samp>global</samp>’</dt>
|
<dd><p>As for ‘<samp>local</samp>’, 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 <samp>-G</samp> setting.
|
</p>
|
</dd>
|
<dt>‘<samp>data</samp>’</dt>
|
<dd><p>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.
|
</p>
|
</dd>
|
<dt>‘<samp>all</samp>’</dt>
|
<dd><p>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.
|
</p>
|
</dd>
|
</dl>
|
|
<p><samp>-mgpopt</samp> is equivalent to <samp>-mgpopt=local</samp>, and
|
<samp>-mno-gpopt</samp> is equivalent to <samp>-mgpopt=none</samp>.
|
</p>
|
<p>The default is <samp>-mgpopt</samp> except when <samp>-fpic</samp> or
|
<samp>-fPIC</samp> is specified to generate position-independent code.
|
Note that the Nios II ABI does not permit GP-relative accesses from
|
shared libraries.
|
</p>
|
<p>You may need to specify <samp>-mno-gpopt</samp> 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.
|
</p>
|
</dd>
|
<dt><code>-mel</code></dt>
|
<dt><code>-meb</code></dt>
|
<dd><a name="index-mel-2"></a>
|
<a name="index-meb-2"></a>
|
<p>Generate little-endian (default) or big-endian (experimental) code,
|
respectively.
|
</p>
|
</dd>
|
<dt><code>-march=<var>arch</var></code></dt>
|
<dd><a name="index-march-9"></a>
|
<p>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: ‘<samp>r1</samp>’, ‘<samp>r2</samp>’.
|
</p>
|
<p>The preprocessor macro <code>__nios2_arch__</code> is available to programs,
|
with value 1 or 2, indicating the targeted ISA level.
|
</p>
|
</dd>
|
<dt><code>-mbypass-cache</code></dt>
|
<dt><code>-mno-bypass-cache</code></dt>
|
<dd><a name="index-mno_002dbypass_002dcache"></a>
|
<a name="index-mbypass_002dcache"></a>
|
<p>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.
|
</p>
|
</dd>
|
<dt><code>-mno-cache-volatile</code></dt>
|
<dt><code>-mcache-volatile</code></dt>
|
<dd><a name="index-mcache_002dvolatile"></a>
|
<a name="index-mno_002dcache_002dvolatile"></a>
|
<p>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.
|
</p>
|
</dd>
|
<dt><code>-mno-fast-sw-div</code></dt>
|
<dt><code>-mfast-sw-div</code></dt>
|
<dd><a name="index-mno_002dfast_002dsw_002ddiv"></a>
|
<a name="index-mfast_002dsw_002ddiv"></a>
|
<p>Do not use table-based fast divide for small numbers. The default
|
is to use the fast divide at <samp>-O3</samp> and above.
|
</p>
|
</dd>
|
<dt><code>-mno-hw-mul</code></dt>
|
<dt><code>-mhw-mul</code></dt>
|
<dt><code>-mno-hw-mulx</code></dt>
|
<dt><code>-mhw-mulx</code></dt>
|
<dt><code>-mno-hw-div</code></dt>
|
<dt><code>-mhw-div</code></dt>
|
<dd><a name="index-mno_002dhw_002dmul"></a>
|
<a name="index-mhw_002dmul"></a>
|
<a name="index-mno_002dhw_002dmulx"></a>
|
<a name="index-mhw_002dmulx"></a>
|
<a name="index-mno_002dhw_002ddiv"></a>
|
<a name="index-mhw_002ddiv"></a>
|
<p>Enable or disable emitting <code>mul</code>, <code>mulx</code> and <code>div</code> family of
|
instructions by the compiler. The default is to emit <code>mul</code>
|
and not emit <code>div</code> and <code>mulx</code>.
|
</p>
|
</dd>
|
<dt><code>-mbmx</code></dt>
|
<dt><code>-mno-bmx</code></dt>
|
<dt><code>-mcdx</code></dt>
|
<dt><code>-mno-cdx</code></dt>
|
<dd><p>Enable or disable generation of Nios II R2 BMX (bit manipulation) and
|
CDX (code density) instructions. Enabling these instructions also
|
requires <samp>-march=r2</samp>. Since these instructions are optional
|
extensions to the R2 architecture, the default is not to emit them.
|
</p>
|
</dd>
|
<dt><code>-mcustom-<var>insn</var>=<var>N</var></code></dt>
|
<dt><code>-mno-custom-<var>insn</var></code></dt>
|
<dd><a name="index-mcustom_002dinsn"></a>
|
<a name="index-mno_002dcustom_002dinsn"></a>
|
<p>Each <samp>-mcustom-<var>insn</var>=<var>N</var></samp> option enables use of a
|
custom instruction with encoding <var>N</var> when generating code that uses
|
<var>insn</var>. For example, <samp>-mcustom-fadds=253</samp> generates custom
|
instruction 253 for single-precision floating-point add operations instead
|
of the default behavior of using a library call.
|
</p>
|
<p>The following values of <var>insn</var> 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 (see <a href="Other-Builtins.html#Other-Builtins">Other Builtins</a>).
|
</p>
|
<p>Single-precision floating point:
|
</p><dl compact="compact">
|
<dt>‘<samp>fadds</samp>’, ‘<samp>fsubs</samp>’, ‘<samp>fdivs</samp>’, ‘<samp>fmuls</samp>’</dt>
|
<dd><p>Binary arithmetic operations.
|
</p>
|
</dd>
|
<dt>‘<samp>fnegs</samp>’</dt>
|
<dd><p>Unary negation.
|
</p>
|
</dd>
|
<dt>‘<samp>fabss</samp>’</dt>
|
<dd><p>Unary absolute value.
|
</p>
|
</dd>
|
<dt>‘<samp>fcmpeqs</samp>’, ‘<samp>fcmpges</samp>’, ‘<samp>fcmpgts</samp>’, ‘<samp>fcmples</samp>’, ‘<samp>fcmplts</samp>’, ‘<samp>fcmpnes</samp>’</dt>
|
<dd><p>Comparison operations.
|
</p>
|
</dd>
|
<dt>‘<samp>fmins</samp>’, ‘<samp>fmaxs</samp>’</dt>
|
<dd><p>Floating-point minimum and maximum. These instructions are only
|
generated if <samp>-ffinite-math-only</samp> is specified.
|
</p>
|
</dd>
|
<dt>‘<samp>fsqrts</samp>’</dt>
|
<dd><p>Unary square root operation.
|
</p>
|
</dd>
|
<dt>‘<samp>fcoss</samp>’, ‘<samp>fsins</samp>’, ‘<samp>ftans</samp>’, ‘<samp>fatans</samp>’, ‘<samp>fexps</samp>’, ‘<samp>flogs</samp>’</dt>
|
<dd><p>Floating-point trigonometric and exponential functions. These instructions
|
are only generated if <samp>-funsafe-math-optimizations</samp> is also specified.
|
</p>
|
</dd>
|
</dl>
|
|
<p>Double-precision floating point:
|
</p><dl compact="compact">
|
<dt>‘<samp>faddd</samp>’, ‘<samp>fsubd</samp>’, ‘<samp>fdivd</samp>’, ‘<samp>fmuld</samp>’</dt>
|
<dd><p>Binary arithmetic operations.
|
</p>
|
</dd>
|
<dt>‘<samp>fnegd</samp>’</dt>
|
<dd><p>Unary negation.
|
</p>
|
</dd>
|
<dt>‘<samp>fabsd</samp>’</dt>
|
<dd><p>Unary absolute value.
|
</p>
|
</dd>
|
<dt>‘<samp>fcmpeqd</samp>’, ‘<samp>fcmpged</samp>’, ‘<samp>fcmpgtd</samp>’, ‘<samp>fcmpled</samp>’, ‘<samp>fcmpltd</samp>’, ‘<samp>fcmpned</samp>’</dt>
|
<dd><p>Comparison operations.
|
</p>
|
</dd>
|
<dt>‘<samp>fmind</samp>’, ‘<samp>fmaxd</samp>’</dt>
|
<dd><p>Double-precision minimum and maximum. These instructions are only
|
generated if <samp>-ffinite-math-only</samp> is specified.
|
</p>
|
</dd>
|
<dt>‘<samp>fsqrtd</samp>’</dt>
|
<dd><p>Unary square root operation.
|
</p>
|
</dd>
|
<dt>‘<samp>fcosd</samp>’, ‘<samp>fsind</samp>’, ‘<samp>ftand</samp>’, ‘<samp>fatand</samp>’, ‘<samp>fexpd</samp>’, ‘<samp>flogd</samp>’</dt>
|
<dd><p>Double-precision trigonometric and exponential functions. These instructions
|
are only generated if <samp>-funsafe-math-optimizations</samp> is also specified.
|
</p>
|
</dd>
|
</dl>
|
|
<p>Conversions:
|
</p><dl compact="compact">
|
<dt>‘<samp>fextsd</samp>’</dt>
|
<dd><p>Conversion from single precision to double precision.
|
</p>
|
</dd>
|
<dt>‘<samp>ftruncds</samp>’</dt>
|
<dd><p>Conversion from double precision to single precision.
|
</p>
|
</dd>
|
<dt>‘<samp>fixsi</samp>’, ‘<samp>fixsu</samp>’, ‘<samp>fixdi</samp>’, ‘<samp>fixdu</samp>’</dt>
|
<dd><p>Conversion from floating point to signed or unsigned integer types, with
|
truncation towards zero.
|
</p>
|
</dd>
|
<dt>‘<samp>round</samp>’</dt>
|
<dd><p>Conversion from single-precision floating point to signed integer,
|
rounding to the nearest integer and ties away from zero.
|
This corresponds to the <code>__builtin_lroundf</code> function when
|
<samp>-fno-math-errno</samp> is used.
|
</p>
|
</dd>
|
<dt>‘<samp>floatis</samp>’, ‘<samp>floatus</samp>’, ‘<samp>floatid</samp>’, ‘<samp>floatud</samp>’</dt>
|
<dd><p>Conversion from signed or unsigned integer types to floating-point types.
|
</p>
|
</dd>
|
</dl>
|
|
<p>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 <var>src1</var> and the most
|
significant half in <var>src2</var>. 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.
|
</p>
|
<dl compact="compact">
|
<dt>‘<samp>fwrx</samp>’</dt>
|
<dd><p>Write <var>src1</var> into the least significant half of X and <var>src2</var> into
|
the most significant half of X.
|
</p>
|
</dd>
|
<dt>‘<samp>fwry</samp>’</dt>
|
<dd><p>Write <var>src1</var> into Y.
|
</p>
|
</dd>
|
<dt>‘<samp>frdxhi</samp>’, ‘<samp>frdxlo</samp>’</dt>
|
<dd><p>Read the most or least (respectively) significant half of X and store it in
|
<var>dest</var>.
|
</p>
|
</dd>
|
<dt>‘<samp>frdy</samp>’</dt>
|
<dd><p>Read the value of Y and store it into <var>dest</var>.
|
</p></dd>
|
</dl>
|
|
<p>Note that you can gain more local control over generation of Nios II custom
|
instructions by using the <code>target("custom-<var>insn</var>=<var>N</var>")</code>
|
and <code>target("no-custom-<var>insn</var>")</code> function attributes
|
(see <a href="Function-Attributes.html#Function-Attributes">Function Attributes</a>)
|
or pragmas (see <a href="Function-Specific-Option-Pragmas.html#Function-Specific-Option-Pragmas">Function Specific Option Pragmas</a>).
|
</p>
|
</dd>
|
<dt><code>-mcustom-fpu-cfg=<var>name</var></code></dt>
|
<dd><a name="index-mcustom_002dfpu_002dcfg"></a>
|
|
<p>This option enables a predefined, named set of custom instruction encodings
|
(see <samp>-mcustom-<var>insn</var></samp> above).
|
Currently, the following sets are defined:
|
</p>
|
<p><samp>-mcustom-fpu-cfg=60-1</samp> is equivalent to:
|
</p><div class="smallexample">
|
<pre class="smallexample">-mcustom-fmuls=252
|
-mcustom-fadds=253
|
-mcustom-fsubs=254
|
-fsingle-precision-constant
|
</pre></div>
|
|
<p><samp>-mcustom-fpu-cfg=60-2</samp> is equivalent to:
|
</p><div class="smallexample">
|
<pre class="smallexample">-mcustom-fmuls=252
|
-mcustom-fadds=253
|
-mcustom-fsubs=254
|
-mcustom-fdivs=255
|
-fsingle-precision-constant
|
</pre></div>
|
|
<p><samp>-mcustom-fpu-cfg=72-3</samp> is equivalent to:
|
</p><div class="smallexample">
|
<pre class="smallexample">-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
|
</pre></div>
|
|
<p>Custom instruction assignments given by individual
|
<samp>-mcustom-<var>insn</var>=</samp> options override those given by
|
<samp>-mcustom-fpu-cfg=</samp>, regardless of the
|
order of the options on the command line.
|
</p>
|
<p>Note that you can gain more local control over selection of a FPU
|
configuration by using the <code>target("custom-fpu-cfg=<var>name</var>")</code>
|
function attribute (see <a href="Function-Attributes.html#Function-Attributes">Function Attributes</a>)
|
or pragma (see <a href="Function-Specific-Option-Pragmas.html#Function-Specific-Option-Pragmas">Function Specific Option Pragmas</a>).
|
</p>
|
</dd>
|
</dl>
|
|
<p>These additional ‘<samp>-m</samp>’ options are available for the Altera Nios II
|
ELF (bare-metal) target:
|
</p>
|
<dl compact="compact">
|
<dt><code>-mhal</code></dt>
|
<dd><a name="index-mhal"></a>
|
<p>Link with HAL BSP. This suppresses linking with the GCC-provided C runtime
|
startup and termination code, and is typically used in conjunction with
|
<samp>-msys-crt0=</samp> to specify the location of the alternate startup code
|
provided by the HAL BSP.
|
</p>
|
</dd>
|
<dt><code>-msmallc</code></dt>
|
<dd><a name="index-msmallc"></a>
|
<p>Link with a limited version of the C library, <samp>-lsmallc</samp>, rather than
|
Newlib.
|
</p>
|
</dd>
|
<dt><code>-msys-crt0=<var>startfile</var></code></dt>
|
<dd><a name="index-msys_002dcrt0"></a>
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<p><var>startfile</var> is the file name of the startfile (crt0) to use
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when linking. This option is only useful in conjunction with <samp>-mhal</samp>.
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</p>
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</dd>
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<dt><code>-msys-lib=<var>systemlib</var></code></dt>
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<dd><a name="index-msys_002dlib"></a>
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<p><var>systemlib</var> is the library name of the library that provides
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low-level system calls required by the C library,
|
e.g. <code>read</code> and <code>write</code>.
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This option is typically used to link with a library provided by a HAL BSP.
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</p>
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</dd>
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</dl>
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