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 <a name="RX-Options"></a>
 <div class="header">
 <p>
 Next: <a href="S_002f390-and-zSeries-Options.html#S_002f390-and-zSeries-Options" accesskey="n" rel="next">S/390 and zSeries Options</a>, Previous: <a href="RS_002f6000-and-PowerPC-Options.html#RS_002f6000-and-PowerPC-Options" accesskey="p" rel="prev">RS/6000 and PowerPC 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>
 </div>
 <hr>
 <a name="RX-Options-1"></a>
 <h4 class="subsection">3.17.39 RX Options</h4>
 <a name="index-RX-Options"></a>

 <p>These command-line options are defined for RX targets:
 </p>
 <dl compact="compact">
 <dt><code>-m64bit-doubles</code></dt>
 <dt><code>-m32bit-doubles</code></dt>
 <dd><a name="index-m64bit_002ddoubles"></a>
 <a name="index-m32bit_002ddoubles"></a>
 <p>Make the <code>double</code> data type be 64 bits (<samp>-m64bit-doubles</samp>)
 or 32 bits (<samp>-m32bit-doubles</samp>) in size.  The default is
 <samp>-m32bit-doubles</samp>.  <em>Note</em> RX floating-point hardware only
 works on 32-bit values, which is why the default is
 <samp>-m32bit-doubles</samp>.
 </p>
 </dd>
 <dt><code>-fpu</code></dt>
 <dt><code>-nofpu</code></dt>
 <dd><a name="index-fpu"></a>
 <a name="index-nofpu"></a>
 <p>Enables (<samp>-fpu</samp>) or disables (<samp>-nofpu</samp>) the use of RX
 floating-point hardware.  The default is enabled for the <var>RX600</var>
 series and disabled for the <var>RX200</var> series.
 </p>
 <p>Floating-point instructions are only generated for 32-bit floating-point
 values, however, so the FPU hardware is not used for doubles if the
 <samp>-m64bit-doubles</samp> option is used.
 </p>
 <p><em>Note</em> If the <samp>-fpu</samp> option is enabled then
 <samp>-funsafe-math-optimizations</samp> is also enabled automatically.
 This is because the RX FPU instructions are themselves unsafe.
 </p>
 </dd>
 <dt><code>-mcpu=<var>name</var></code></dt>
 <dd><a name="index-_002dmcpu"></a>
 <p>Selects the type of RX CPU to be targeted.  Currently three types are
 supported, the generic <var>RX600</var> and <var>RX200</var> series hardware and
 the specific <var>RX610</var> CPU.  The default is <var>RX600</var>.
 </p>
 <p>The only difference between <var>RX600</var> and <var>RX610</var> is that the
 <var>RX610</var> does not support the <code>MVTIPL</code> instruction.
 </p>
 <p>The <var>RX200</var> series does not have a hardware floating-point unit
 and so <samp>-nofpu</samp> is enabled by default when this type is
 selected.
 </p>
 </dd>
 <dt><code>-mbig-endian-data</code></dt>
 <dt><code>-mlittle-endian-data</code></dt>
 <dd><a name="index-mbig_002dendian_002ddata"></a>
 <a name="index-mlittle_002dendian_002ddata"></a>
 <p>Store data (but not code) in the big-endian format.  The default is
 <samp>-mlittle-endian-data</samp>, i.e. to store data in the little-endian
 format.
 </p>
 </dd>
 <dt><code>-msmall-data-limit=<var>N</var></code></dt>
 <dd><a name="index-msmall_002ddata_002dlimit"></a>
 <p>Specifies the maximum size in bytes of global and static variables
 which can be placed into the small data area.  Using the small data
 area can lead to smaller and faster code, but the size of area is
 limited and it is up to the programmer to ensure that the area does
 not overflow.  Also when the small data area is used one of the RX&rsquo;s
 registers (usually <code>r13</code>) is reserved for use pointing to this
 area, so it is no longer available for use by the compiler.  This
 could result in slower and/or larger code if variables are pushed onto
 the stack instead of being held in this register.
 </p>
 <p>Note, common variables (variables that have not been initialized) and
 constants are not placed into the small data area as they are assigned
 to other sections in the output executable.
 </p>
 <p>The default value is zero, which disables this feature.  Note, this
 feature is not enabled by default with higher optimization levels
 (<samp>-O2</samp> etc) because of the potentially detrimental effects of
 reserving a register.  It is up to the programmer to experiment and
 discover whether this feature is of benefit to their program.  See the
 description of the <samp>-mpid</samp> option for a description of how the
 actual register to hold the small data area pointer is chosen.
 </p>
 </dd>
 <dt><code>-msim</code></dt>
 <dt><code>-mno-sim</code></dt>
 <dd><a name="index-msim-8"></a>
 <a name="index-mno_002dsim"></a>
 <p>Use the simulator runtime.  The default is to use the libgloss
 board-specific runtime.
 </p>
 </dd>
 <dt><code>-mas100-syntax</code></dt>
 <dt><code>-mno-as100-syntax</code></dt>
 <dd><a name="index-mas100_002dsyntax"></a>
 <a name="index-mno_002das100_002dsyntax"></a>
 <p>When generating assembler output use a syntax that is compatible with
 Renesas&rsquo;s AS100 assembler.  This syntax can also be handled by the GAS
 assembler, but it has some restrictions so it is not generated by default.
 </p>
 </dd>
 <dt><code>-mmax-constant-size=<var>N</var></code></dt>
 <dd><a name="index-mmax_002dconstant_002dsize"></a>
 <p>Specifies the maximum size, in bytes, of a constant that can be used as
 an operand in a RX instruction.  Although the RX instruction set does
 allow constants of up to 4 bytes in length to be used in instructions,
 a longer value equates to a longer instruction.  Thus in some
 circumstances it can be beneficial to restrict the size of constants
 that are used in instructions.  Constants that are too big are instead
 placed into a constant pool and referenced via register indirection.
 </p>
 <p>The value <var>N</var> can be between 0 and 4.  A value of 0 (the default)
 or 4 means that constants of any size are allowed.
 </p>
 </dd>
 <dt><code>-mrelax</code></dt>
 <dd><a name="index-mrelax-5"></a>
 <p>Enable linker relaxation.  Linker relaxation is a process whereby the
 linker attempts to reduce the size of a program by finding shorter
 versions of various instructions.  Disabled by default.
 </p>
 </dd>
 <dt><code>-mint-register=<var>N</var></code></dt>
 <dd><a name="index-mint_002dregister"></a>
 <p>Specify the number of registers to reserve for fast interrupt handler
 functions.  The value <var>N</var> can be between 0 and 4.  A value of 1
 means that register <code>r13</code> is reserved for the exclusive use
 of fast interrupt handlers.  A value of 2 reserves <code>r13</code> and
 <code>r12</code>.  A value of 3 reserves <code>r13</code>, <code>r12</code> and
 <code>r11</code>, and a value of 4 reserves <code>r13</code> through <code>r10</code>.
 A value of 0, the default, does not reserve any registers.
 </p>
 </dd>
 <dt><code>-msave-acc-in-interrupts</code></dt>
 <dd><a name="index-msave_002dacc_002din_002dinterrupts"></a>
 <p>Specifies that interrupt handler functions should preserve the
 accumulator register.  This is only necessary if normal code might use
 the accumulator register, for example because it performs 64-bit
 multiplications.  The default is to ignore the accumulator as this
 makes the interrupt handlers faster.
 </p>
 </dd>
 <dt><code>-mpid</code></dt>
 <dt><code>-mno-pid</code></dt>
 <dd><a name="index-mpid"></a>
 <a name="index-mno_002dpid"></a>
 <p>Enables the generation of position independent data.  When enabled any
 access to constant data is done via an offset from a base address
 held in a register.  This allows the location of constant data to be
 determined at run time without requiring the executable to be
 relocated, which is a benefit to embedded applications with tight
 memory constraints.  Data that can be modified is not affected by this
 option.
 </p>
 <p>Note, using this feature reserves a register, usually <code>r13</code>, for
 the constant data base address.  This can result in slower and/or
 larger code, especially in complicated functions.
 </p>
 <p>The actual register chosen to hold the constant data base address
 depends upon whether the <samp>-msmall-data-limit</samp> and/or the
 <samp>-mint-register</samp> command-line options are enabled.  Starting
 with register <code>r13</code> and proceeding downwards, registers are
 allocated first to satisfy the requirements of <samp>-mint-register</samp>,
 then <samp>-mpid</samp> and finally <samp>-msmall-data-limit</samp>.  Thus it
 is possible for the small data area register to be <code>r8</code> if both
 <samp>-mint-register=4</samp> and <samp>-mpid</samp> are specified on the
 command line.
 </p>
 <p>By default this feature is not enabled.  The default can be restored
 via the <samp>-mno-pid</samp> command-line option.
 </p>
 </dd>
 <dt><code>-mno-warn-multiple-fast-interrupts</code></dt>
 <dt><code>-mwarn-multiple-fast-interrupts</code></dt>
 <dd><a name="index-mno_002dwarn_002dmultiple_002dfast_002dinterrupts"></a>
 <a name="index-mwarn_002dmultiple_002dfast_002dinterrupts"></a>
 <p>Prevents GCC from issuing a warning message if it finds more than one
 fast interrupt handler when it is compiling a file.  The default is to
 issue a warning for each extra fast interrupt handler found, as the RX
 only supports one such interrupt.
 </p>
 </dd>
 </dl>

 <p><em>Note:</em> The generic GCC command-line option <samp>-ffixed-<var>reg</var></samp>
 has special significance to the RX port when used with the
 <code>interrupt</code> function attribute.  This attribute indicates a
 function intended to process fast interrupts.  GCC ensures
 that it only uses the registers <code>r10</code>, <code>r11</code>, <code>r12</code>
 and/or <code>r13</code> and only provided that the normal use of the
 corresponding registers have been restricted via the
 <samp>-ffixed-<var>reg</var></samp> or <samp>-mint-register</samp> command-line
 options.
 </p>
 <hr>
 <div class="header">
 <p>
 Next: <a href="S_002f390-and-zSeries-Options.html#S_002f390-and-zSeries-Options" accesskey="n" rel="next">S/390 and zSeries Options</a>, Previous: <a href="RS_002f6000-and-PowerPC-Options.html#RS_002f6000-and-PowerPC-Options" accesskey="p" rel="prev">RS/6000 and PowerPC 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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	<a name="RX-Options"></a>
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	<p>
	Next: <a href="S_002f390-and-zSeries-Options.html#S_002f390-and-zSeries-Options" accesskey="n" rel="next">S/390 and zSeries Options</a>, Previous: <a href="RS_002f6000-and-PowerPC-Options.html#RS_002f6000-and-PowerPC-Options" accesskey="p" rel="prev">RS/6000 and PowerPC 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>
	</div>
	<hr>
	<a name="RX-Options-1"></a>
	<h4 class="subsection">3.17.39 RX Options</h4>
	<a name="index-RX-Options"></a>

	<p>These command-line options are defined for RX targets:
	</p>
	<dl compact="compact">
	<dt><code>-m64bit-doubles</code></dt>
	<dt><code>-m32bit-doubles</code></dt>
	<dd><a name="index-m64bit_002ddoubles"></a>
	<a name="index-m32bit_002ddoubles"></a>
	<p>Make the <code>double</code> data type be 64 bits (<samp>-m64bit-doubles</samp>)
	or 32 bits (<samp>-m32bit-doubles</samp>) in size. The default is
	<samp>-m32bit-doubles</samp>. <em>Note</em> RX floating-point hardware only
	works on 32-bit values, which is why the default is
	<samp>-m32bit-doubles</samp>.
	</p>
	</dd>
	<dt><code>-fpu</code></dt>
	<dt><code>-nofpu</code></dt>
	<dd><a name="index-fpu"></a>
	<a name="index-nofpu"></a>
	<p>Enables (<samp>-fpu</samp>) or disables (<samp>-nofpu</samp>) the use of RX
	floating-point hardware. The default is enabled for the <var>RX600</var>
	series and disabled for the <var>RX200</var> series.
	</p>
	<p>Floating-point instructions are only generated for 32-bit floating-point
	values, however, so the FPU hardware is not used for doubles if the
	<samp>-m64bit-doubles</samp> option is used.
	</p>
	<p><em>Note</em> If the <samp>-fpu</samp> option is enabled then
	<samp>-funsafe-math-optimizations</samp> is also enabled automatically.
	This is because the RX FPU instructions are themselves unsafe.
	</p>
	</dd>
	<dt><code>-mcpu=<var>name</var></code></dt>
	<dd><a name="index-_002dmcpu"></a>
	<p>Selects the type of RX CPU to be targeted. Currently three types are
	supported, the generic <var>RX600</var> and <var>RX200</var> series hardware and
	the specific <var>RX610</var> CPU. The default is <var>RX600</var>.
	</p>
	<p>The only difference between <var>RX600</var> and <var>RX610</var> is that the
	<var>RX610</var> does not support the <code>MVTIPL</code> instruction.
	</p>
	<p>The <var>RX200</var> series does not have a hardware floating-point unit
	and so <samp>-nofpu</samp> is enabled by default when this type is
	selected.
	</p>
	</dd>
	<dt><code>-mbig-endian-data</code></dt>
	<dt><code>-mlittle-endian-data</code></dt>
	<dd><a name="index-mbig_002dendian_002ddata"></a>
	<a name="index-mlittle_002dendian_002ddata"></a>
	<p>Store data (but not code) in the big-endian format. The default is
	<samp>-mlittle-endian-data</samp>, i.e. to store data in the little-endian
	format.
	</p>
	</dd>
	<dt><code>-msmall-data-limit=<var>N</var></code></dt>
	<dd><a name="index-msmall_002ddata_002dlimit"></a>
	<p>Specifies the maximum size in bytes of global and static variables
	which can be placed into the small data area. Using the small data
	area can lead to smaller and faster code, but the size of area is
	limited and it is up to the programmer to ensure that the area does
	not overflow. Also when the small data area is used one of the RX’s
	registers (usually <code>r13</code>) is reserved for use pointing to this
	area, so it is no longer available for use by the compiler. This
	could result in slower and/or larger code if variables are pushed onto
	the stack instead of being held in this register.
	</p>
	<p>Note, common variables (variables that have not been initialized) and
	constants are not placed into the small data area as they are assigned
	to other sections in the output executable.
	</p>
	<p>The default value is zero, which disables this feature. Note, this
	feature is not enabled by default with higher optimization levels
	(<samp>-O2</samp> etc) because of the potentially detrimental effects of
	reserving a register. It is up to the programmer to experiment and
	discover whether this feature is of benefit to their program. See the
	description of the <samp>-mpid</samp> option for a description of how the
	actual register to hold the small data area pointer is chosen.
	</p>
	</dd>
	<dt><code>-msim</code></dt>
	<dt><code>-mno-sim</code></dt>
	<dd><a name="index-msim-8"></a>
	<a name="index-mno_002dsim"></a>
	<p>Use the simulator runtime. The default is to use the libgloss
	board-specific runtime.
	</p>
	</dd>
	<dt><code>-mas100-syntax</code></dt>
	<dt><code>-mno-as100-syntax</code></dt>
	<dd><a name="index-mas100_002dsyntax"></a>
	<a name="index-mno_002das100_002dsyntax"></a>
	<p>When generating assembler output use a syntax that is compatible with
	Renesas’s AS100 assembler. This syntax can also be handled by the GAS
	assembler, but it has some restrictions so it is not generated by default.
	</p>
	</dd>
	<dt><code>-mmax-constant-size=<var>N</var></code></dt>
	<dd><a name="index-mmax_002dconstant_002dsize"></a>
	<p>Specifies the maximum size, in bytes, of a constant that can be used as
	an operand in a RX instruction. Although the RX instruction set does
	allow constants of up to 4 bytes in length to be used in instructions,
	a longer value equates to a longer instruction. Thus in some
	circumstances it can be beneficial to restrict the size of constants
	that are used in instructions. Constants that are too big are instead
	placed into a constant pool and referenced via register indirection.
	</p>
	<p>The value <var>N</var> can be between 0 and 4. A value of 0 (the default)
	or 4 means that constants of any size are allowed.
	</p>
	</dd>
	<dt><code>-mrelax</code></dt>
	<dd><a name="index-mrelax-5"></a>
	<p>Enable linker relaxation. Linker relaxation is a process whereby the
	linker attempts to reduce the size of a program by finding shorter
	versions of various instructions. Disabled by default.
	</p>
	</dd>
	<dt><code>-mint-register=<var>N</var></code></dt>
	<dd><a name="index-mint_002dregister"></a>
	<p>Specify the number of registers to reserve for fast interrupt handler
	functions. The value <var>N</var> can be between 0 and 4. A value of 1
	means that register <code>r13</code> is reserved for the exclusive use
	of fast interrupt handlers. A value of 2 reserves <code>r13</code> and
	<code>r12</code>. A value of 3 reserves <code>r13</code>, <code>r12</code> and
	<code>r11</code>, and a value of 4 reserves <code>r13</code> through <code>r10</code>.
	A value of 0, the default, does not reserve any registers.
	</p>
	</dd>
	<dt><code>-msave-acc-in-interrupts</code></dt>
	<dd><a name="index-msave_002dacc_002din_002dinterrupts"></a>
	<p>Specifies that interrupt handler functions should preserve the
	accumulator register. This is only necessary if normal code might use
	the accumulator register, for example because it performs 64-bit
	multiplications. The default is to ignore the accumulator as this
	makes the interrupt handlers faster.
	</p>
	</dd>
	<dt><code>-mpid</code></dt>
	<dt><code>-mno-pid</code></dt>
	<dd><a name="index-mpid"></a>
	<a name="index-mno_002dpid"></a>
	<p>Enables the generation of position independent data. When enabled any
	access to constant data is done via an offset from a base address
	held in a register. This allows the location of constant data to be
	determined at run time without requiring the executable to be
	relocated, which is a benefit to embedded applications with tight
	memory constraints. Data that can be modified is not affected by this
	option.
	</p>
	<p>Note, using this feature reserves a register, usually <code>r13</code>, for
	the constant data base address. This can result in slower and/or
	larger code, especially in complicated functions.
	</p>
	<p>The actual register chosen to hold the constant data base address
	depends upon whether the <samp>-msmall-data-limit</samp> and/or the
	<samp>-mint-register</samp> command-line options are enabled. Starting
	with register <code>r13</code> and proceeding downwards, registers are
	allocated first to satisfy the requirements of <samp>-mint-register</samp>,
	then <samp>-mpid</samp> and finally <samp>-msmall-data-limit</samp>. Thus it
	is possible for the small data area register to be <code>r8</code> if both
	<samp>-mint-register=4</samp> and <samp>-mpid</samp> are specified on the
	command line.
	</p>
	<p>By default this feature is not enabled. The default can be restored
	via the <samp>-mno-pid</samp> command-line option.
	</p>
	</dd>
	<dt><code>-mno-warn-multiple-fast-interrupts</code></dt>
	<dt><code>-mwarn-multiple-fast-interrupts</code></dt>
	<dd><a name="index-mno_002dwarn_002dmultiple_002dfast_002dinterrupts"></a>
	<a name="index-mwarn_002dmultiple_002dfast_002dinterrupts"></a>
	<p>Prevents GCC from issuing a warning message if it finds more than one
	fast interrupt handler when it is compiling a file. The default is to
	issue a warning for each extra fast interrupt handler found, as the RX
	only supports one such interrupt.
	</p>
	</dd>
	</dl>

	<p><em>Note:</em> The generic GCC command-line option <samp>-ffixed-<var>reg</var></samp>
	has special significance to the RX port when used with the
	<code>interrupt</code> function attribute. This attribute indicates a
	function intended to process fast interrupts. GCC ensures
	that it only uses the registers <code>r10</code>, <code>r11</code>, <code>r12</code>
	and/or <code>r13</code> and only provided that the normal use of the
	corresponding registers have been restricted via the
	<samp>-ffixed-<var>reg</var></samp> or <samp>-mint-register</samp> command-line
	options.
	</p>
	<hr>
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