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<a name="Nios-II-Options"></a>
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<p>
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> &nbsp; [<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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<hr>
<a name="Nios-II-Options-1"></a>
<h4 class="subsection">3.19.35 Nios II Options</h4>
<a name="index-Nios-II-options"></a>
<a name="index-Altera-Nios-II-options"></a>

<p>These are the options defined for the Altera Nios II processor.
</p>
<dl compact="compact">
<dt><code>-G <var>num</var></code></dt>
<dd><a name="index-G-3"></a>
<a name="index-smaller-data-references-1"></a>
<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.
</p>
</dd>
<dt><code>-mgpopt=<var>option</var></code></dt>
<dt><code>-mgpopt</code></dt>
<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>&lsquo;<samp>none</samp>&rsquo;</dt>
<dd><p>Do not generate GP-relative accesses.
</p>
</dd>
<dt>&lsquo;<samp>local</samp>&rsquo;</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>&lsquo;<samp>global</samp>&rsquo;</dt>
<dd><p>As for &lsquo;<samp>local</samp>&rsquo;, 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>&lsquo;<samp>data</samp>&rsquo;</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>&lsquo;<samp>all</samp>&rsquo;</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>-mgprel-sec=<var>regexp</var></code></dt>
<dd><a name="index-mgprel_002dsec"></a>
<p>This option specifies additional section names that can be accessed via
GP-relative addressing.  It is most useful in conjunction with 
<code>section</code> attributes on variable declarations 
(see <a href="Common-Variable-Attributes.html#Common-Variable-Attributes">Common Variable Attributes</a>) and a custom linker script.  
The <var>regexp</var> is a POSIX Extended Regular Expression.
</p>
<p>This option does not affect the behavior of the <samp>-G</samp> option, and 
the specified sections are in addition to the standard <code>.sdata</code>
and <code>.sbss</code> small-data sections that are recognized by <samp>-mgpopt</samp>.
</p>
</dd>
<dt><code>-mr0rel-sec=<var>regexp</var></code></dt>
<dd><a name="index-mr0rel_002dsec"></a>
<p>This option specifies names of sections that can be accessed via a 
16-bit offset from <code>r0</code>; that is, in the low 32K or high 32K 
of the 32-bit address space.  It is most useful in conjunction with 
<code>section</code> attributes on variable declarations 
(see <a href="Common-Variable-Attributes.html#Common-Variable-Attributes">Common Variable Attributes</a>) and a custom linker script.  
The <var>regexp</var> is a POSIX Extended Regular Expression.
</p>
<p>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.
</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-10"></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: &lsquo;<samp>r1</samp>&rsquo;, &lsquo;<samp>r2</samp>&rsquo;.
</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>&lsquo;<samp>fadds</samp>&rsquo;, &lsquo;<samp>fsubs</samp>&rsquo;, &lsquo;<samp>fdivs</samp>&rsquo;, &lsquo;<samp>fmuls</samp>&rsquo;</dt>
<dd><p>Binary arithmetic operations.
</p>
</dd>
<dt>&lsquo;<samp>fnegs</samp>&rsquo;</dt>
<dd><p>Unary negation.
</p>
</dd>
<dt>&lsquo;<samp>fabss</samp>&rsquo;</dt>
<dd><p>Unary absolute value.
</p>
</dd>
<dt>&lsquo;<samp>fcmpeqs</samp>&rsquo;, &lsquo;<samp>fcmpges</samp>&rsquo;, &lsquo;<samp>fcmpgts</samp>&rsquo;, &lsquo;<samp>fcmples</samp>&rsquo;, &lsquo;<samp>fcmplts</samp>&rsquo;, &lsquo;<samp>fcmpnes</samp>&rsquo;</dt>
<dd><p>Comparison operations.
</p>
</dd>
<dt>&lsquo;<samp>fmins</samp>&rsquo;, &lsquo;<samp>fmaxs</samp>&rsquo;</dt>
<dd><p>Floating-point minimum and maximum.  These instructions are only
generated if <samp>-ffinite-math-only</samp> is specified.
</p>
</dd>
<dt>&lsquo;<samp>fsqrts</samp>&rsquo;</dt>
<dd><p>Unary square root operation.
</p>
</dd>
<dt>&lsquo;<samp>fcoss</samp>&rsquo;, &lsquo;<samp>fsins</samp>&rsquo;, &lsquo;<samp>ftans</samp>&rsquo;, &lsquo;<samp>fatans</samp>&rsquo;, &lsquo;<samp>fexps</samp>&rsquo;, &lsquo;<samp>flogs</samp>&rsquo;</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>&lsquo;<samp>faddd</samp>&rsquo;, &lsquo;<samp>fsubd</samp>&rsquo;, &lsquo;<samp>fdivd</samp>&rsquo;, &lsquo;<samp>fmuld</samp>&rsquo;</dt>
<dd><p>Binary arithmetic operations.
</p>
</dd>
<dt>&lsquo;<samp>fnegd</samp>&rsquo;</dt>
<dd><p>Unary negation.
</p>
</dd>
<dt>&lsquo;<samp>fabsd</samp>&rsquo;</dt>
<dd><p>Unary absolute value.
</p>
</dd>
<dt>&lsquo;<samp>fcmpeqd</samp>&rsquo;, &lsquo;<samp>fcmpged</samp>&rsquo;, &lsquo;<samp>fcmpgtd</samp>&rsquo;, &lsquo;<samp>fcmpled</samp>&rsquo;, &lsquo;<samp>fcmpltd</samp>&rsquo;, &lsquo;<samp>fcmpned</samp>&rsquo;</dt>
<dd><p>Comparison operations.
</p>
</dd>
<dt>&lsquo;<samp>fmind</samp>&rsquo;, &lsquo;<samp>fmaxd</samp>&rsquo;</dt>
<dd><p>Double-precision minimum and maximum.  These instructions are only
generated if <samp>-ffinite-math-only</samp> is specified.
</p>
</dd>
<dt>&lsquo;<samp>fsqrtd</samp>&rsquo;</dt>
<dd><p>Unary square root operation.
</p>
</dd>
<dt>&lsquo;<samp>fcosd</samp>&rsquo;, &lsquo;<samp>fsind</samp>&rsquo;, &lsquo;<samp>ftand</samp>&rsquo;, &lsquo;<samp>fatand</samp>&rsquo;, &lsquo;<samp>fexpd</samp>&rsquo;, &lsquo;<samp>flogd</samp>&rsquo;</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>&lsquo;<samp>fextsd</samp>&rsquo;</dt>
<dd><p>Conversion from single precision to double precision.
</p>
</dd>
<dt>&lsquo;<samp>ftruncds</samp>&rsquo;</dt>
<dd><p>Conversion from double precision to single precision.
</p>
</dd>
<dt>&lsquo;<samp>fixsi</samp>&rsquo;, &lsquo;<samp>fixsu</samp>&rsquo;, &lsquo;<samp>fixdi</samp>&rsquo;, &lsquo;<samp>fixdu</samp>&rsquo;</dt>
<dd><p>Conversion from floating point to signed or unsigned integer types, with
truncation towards zero.
</p>
</dd>
<dt>&lsquo;<samp>round</samp>&rsquo;</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>&lsquo;<samp>floatis</samp>&rsquo;, &lsquo;<samp>floatus</samp>&rsquo;, &lsquo;<samp>floatid</samp>&rsquo;, &lsquo;<samp>floatud</samp>&rsquo;</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>&lsquo;<samp>fwrx</samp>&rsquo;</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>&lsquo;<samp>fwry</samp>&rsquo;</dt>
<dd><p>Write <var>src1</var> into Y.
</p>
</dd>
<dt>&lsquo;<samp>frdxhi</samp>&rsquo;, &lsquo;<samp>frdxlo</samp>&rsquo;</dt>
<dd><p>Read the most or least (respectively) significant half of X and store it in
<var>dest</var>.
</p>
</dd>
<dt>&lsquo;<samp>frdy</samp>&rsquo;</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(&quot;custom-<var>insn</var>=<var>N</var>&quot;)</code>
and <code>target(&quot;no-custom-<var>insn</var>&quot;)</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(&quot;custom-fpu-cfg=<var>name</var>&quot;)</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 &lsquo;<samp>-m</samp>&rsquo; 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>
<p><var>startfile</var> is the file name of the startfile (crt0) to use 
when linking.  This option is only useful in conjunction with <samp>-mhal</samp>.
</p>
</dd>
<dt><code>-msys-lib=<var>systemlib</var></code></dt>
<dd><a name="index-msys_002dlib"></a>
<p><var>systemlib</var> is the library name of the library that provides
low-level system calls required by the C library,
e.g. <code>read</code> and <code>write</code>.
This option is typically used to link with a library provided by a HAL BSP.
</p>
</dd>
</dl>

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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> &nbsp; [<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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