361 lines
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361 lines
17 KiB
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<head>
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<title>Using the GNU Compiler Collection (GCC): S/390 and zSeries Options</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): S/390 and zSeries Options">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Submodel-Options.html#Submodel-Options" rel="up" title="Submodel Options">
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<link href="Score-Options.html#Score-Options" rel="next" title="Score Options">
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<link href="RX-Options.html#RX-Options" rel="prev" title="RX Options">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="S_002f390-and-zSeries-Options"></a>
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<div class="header">
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<p>
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Next: <a href="Score-Options.html#Score-Options" accesskey="n" rel="next">Score Options</a>, Previous: <a href="RX-Options.html#RX-Options" accesskey="p" rel="prev">RX 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="S_002f390-and-zSeries-Options-1"></a>
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<h4 class="subsection">3.18.40 S/390 and zSeries Options</h4>
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<a name="index-S_002f390-and-zSeries-Options"></a>
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<p>These are the ‘<samp>-m</samp>’ options defined for the S/390 and zSeries architecture.
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</p>
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<dl compact="compact">
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<dt><code>-mhard-float</code></dt>
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<dt><code>-msoft-float</code></dt>
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<dd><a name="index-mhard_002dfloat-5"></a>
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<a name="index-msoft_002dfloat-9"></a>
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<p>Use (do not use) the hardware floating-point instructions and registers
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for floating-point operations. When <samp>-msoft-float</samp> is specified,
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functions in <samp>libgcc.a</samp> are used to perform floating-point
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operations. When <samp>-mhard-float</samp> is specified, the compiler
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generates IEEE floating-point instructions. This is the default.
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</p>
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</dd>
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<dt><code>-mhard-dfp</code></dt>
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<dt><code>-mno-hard-dfp</code></dt>
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<dd><a name="index-mhard_002ddfp-1"></a>
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<a name="index-mno_002dhard_002ddfp-1"></a>
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<p>Use (do not use) the hardware decimal-floating-point instructions for
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decimal-floating-point operations. When <samp>-mno-hard-dfp</samp> is
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specified, functions in <samp>libgcc.a</samp> are used to perform
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decimal-floating-point operations. When <samp>-mhard-dfp</samp> is
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specified, the compiler generates decimal-floating-point hardware
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instructions. This is the default for <samp>-march=z9-ec</samp> or higher.
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</p>
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</dd>
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<dt><code>-mlong-double-64</code></dt>
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<dt><code>-mlong-double-128</code></dt>
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<dd><a name="index-mlong_002ddouble_002d64"></a>
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<a name="index-mlong_002ddouble_002d128"></a>
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<p>These switches control the size of <code>long double</code> type. A size
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of 64 bits makes the <code>long double</code> type equivalent to the <code>double</code>
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type. This is the default.
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</p>
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</dd>
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<dt><code>-mbackchain</code></dt>
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<dt><code>-mno-backchain</code></dt>
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<dd><a name="index-mbackchain"></a>
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<a name="index-mno_002dbackchain"></a>
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<p>Store (do not store) the address of the caller’s frame as backchain pointer
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into the callee’s stack frame.
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A backchain may be needed to allow debugging using tools that do not understand
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DWARF call frame information.
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When <samp>-mno-packed-stack</samp> is in effect, the backchain pointer is stored
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at the bottom of the stack frame; when <samp>-mpacked-stack</samp> is in effect,
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the backchain is placed into the topmost word of the 96/160 byte register
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save area.
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</p>
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<p>In general, code compiled with <samp>-mbackchain</samp> is call-compatible with
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code compiled with <samp>-mmo-backchain</samp>; however, use of the backchain
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for debugging purposes usually requires that the whole binary is built with
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<samp>-mbackchain</samp>. Note that the combination of <samp>-mbackchain</samp>,
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<samp>-mpacked-stack</samp> and <samp>-mhard-float</samp> is not supported. In order
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to build a linux kernel use <samp>-msoft-float</samp>.
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</p>
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<p>The default is to not maintain the backchain.
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</p>
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</dd>
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<dt><code>-mpacked-stack</code></dt>
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<dt><code>-mno-packed-stack</code></dt>
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<dd><a name="index-mpacked_002dstack"></a>
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<a name="index-mno_002dpacked_002dstack"></a>
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<p>Use (do not use) the packed stack layout. When <samp>-mno-packed-stack</samp> is
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specified, the compiler uses the all fields of the 96/160 byte register save
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area only for their default purpose; unused fields still take up stack space.
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When <samp>-mpacked-stack</samp> is specified, register save slots are densely
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packed at the top of the register save area; unused space is reused for other
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purposes, allowing for more efficient use of the available stack space.
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However, when <samp>-mbackchain</samp> is also in effect, the topmost word of
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the save area is always used to store the backchain, and the return address
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register is always saved two words below the backchain.
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</p>
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<p>As long as the stack frame backchain is not used, code generated with
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<samp>-mpacked-stack</samp> is call-compatible with code generated with
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<samp>-mno-packed-stack</samp>. Note that some non-FSF releases of GCC 2.95 for
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S/390 or zSeries generated code that uses the stack frame backchain at run
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time, not just for debugging purposes. Such code is not call-compatible
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with code compiled with <samp>-mpacked-stack</samp>. Also, note that the
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combination of <samp>-mbackchain</samp>,
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<samp>-mpacked-stack</samp> and <samp>-mhard-float</samp> is not supported. In order
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to build a linux kernel use <samp>-msoft-float</samp>.
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</p>
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<p>The default is to not use the packed stack layout.
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</p>
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</dd>
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<dt><code>-msmall-exec</code></dt>
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<dt><code>-mno-small-exec</code></dt>
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<dd><a name="index-msmall_002dexec"></a>
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<a name="index-mno_002dsmall_002dexec"></a>
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<p>Generate (or do not generate) code using the <code>bras</code> instruction
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to do subroutine calls.
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This only works reliably if the total executable size does not
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exceed 64k. The default is to use the <code>basr</code> instruction instead,
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which does not have this limitation.
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</p>
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</dd>
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<dt><code>-m64</code></dt>
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<dt><code>-m31</code></dt>
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<dd><a name="index-m64-2"></a>
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<a name="index-m31"></a>
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<p>When <samp>-m31</samp> is specified, generate code compliant to the
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GNU/Linux for S/390 ABI. When <samp>-m64</samp> is specified, generate
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code compliant to the GNU/Linux for zSeries ABI. This allows GCC in
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particular to generate 64-bit instructions. For the ‘<samp>s390</samp>’
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targets, the default is <samp>-m31</samp>, while the ‘<samp>s390x</samp>’
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targets default to <samp>-m64</samp>.
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</p>
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</dd>
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<dt><code>-mzarch</code></dt>
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<dt><code>-mesa</code></dt>
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<dd><a name="index-mzarch"></a>
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<a name="index-mesa"></a>
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<p>When <samp>-mzarch</samp> is specified, generate code using the
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instructions available on z/Architecture.
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When <samp>-mesa</samp> is specified, generate code using the
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instructions available on ESA/390. Note that <samp>-mesa</samp> is
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not possible with <samp>-m64</samp>.
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When generating code compliant to the GNU/Linux for S/390 ABI,
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the default is <samp>-mesa</samp>. When generating code compliant
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to the GNU/Linux for zSeries ABI, the default is <samp>-mzarch</samp>.
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</p>
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</dd>
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<dt><code>-mhtm</code></dt>
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<dt><code>-mno-htm</code></dt>
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<dd><a name="index-mhtm-1"></a>
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<a name="index-mno_002dhtm-1"></a>
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<p>The <samp>-mhtm</samp> option enables a set of builtins making use of
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instructions available with the transactional execution facility
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introduced with the IBM zEnterprise EC12 machine generation
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<a href="S_002f390-System-z-Built_002din-Functions.html#S_002f390-System-z-Built_002din-Functions">S/390 System z Built-in Functions</a>.
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<samp>-mhtm</samp> is enabled by default when using <samp>-march=zEC12</samp>.
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</p>
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</dd>
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<dt><code>-mvx</code></dt>
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<dt><code>-mno-vx</code></dt>
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<dd><a name="index-mvx"></a>
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<a name="index-mno_002dvx"></a>
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<p>When <samp>-mvx</samp> is specified, generate code using the instructions
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available with the vector extension facility introduced with the IBM
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z13 machine generation.
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This option changes the ABI for some vector type values with regard to
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alignment and calling conventions. In case vector type values are
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being used in an ABI-relevant context a GAS ‘<samp>.gnu_attribute</samp>’
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command will be added to mark the resulting binary with the ABI used.
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<samp>-mvx</samp> is enabled by default when using <samp>-march=z13</samp>.
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</p>
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</dd>
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<dt><code>-mzvector</code></dt>
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<dt><code>-mno-zvector</code></dt>
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<dd><a name="index-mzvector"></a>
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<a name="index-mno_002dzvector"></a>
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<p>The <samp>-mzvector</samp> option enables vector language extensions and
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builtins using instructions available with the vector extension
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facility introduced with the IBM z13 machine generation.
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This option adds support for ‘<samp>vector</samp>’ to be used as a keyword to
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define vector type variables and arguments. ‘<samp>vector</samp>’ is only
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available when GNU extensions are enabled. It will not be expanded
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when requesting strict standard compliance e.g. with <samp>-std=c99</samp>.
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In addition to the GCC low-level builtins <samp>-mzvector</samp> enables
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a set of builtins added for compatibility with AltiVec-style
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implementations like Power and Cell. In order to make use of these
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builtins the header file <samp>vecintrin.h</samp> needs to be included.
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<samp>-mzvector</samp> is disabled by default.
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</p>
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</dd>
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<dt><code>-mmvcle</code></dt>
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<dt><code>-mno-mvcle</code></dt>
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<dd><a name="index-mmvcle"></a>
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<a name="index-mno_002dmvcle"></a>
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<p>Generate (or do not generate) code using the <code>mvcle</code> instruction
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to perform block moves. When <samp>-mno-mvcle</samp> is specified,
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use a <code>mvc</code> loop instead. This is the default unless optimizing for
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size.
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</p>
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</dd>
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<dt><code>-mdebug</code></dt>
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<dt><code>-mno-debug</code></dt>
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<dd><a name="index-mdebug-1"></a>
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<a name="index-mno_002ddebug"></a>
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<p>Print (or do not print) additional debug information when compiling.
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The default is to not print debug information.
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</p>
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</dd>
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<dt><code>-march=<var>cpu-type</var></code></dt>
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<dd><a name="index-march-10"></a>
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<p>Generate code that runs on <var>cpu-type</var>, which is the name of a
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system representing a certain processor type. Possible values for
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<var>cpu-type</var> are ‘<samp>z900</samp>’, ‘<samp>z990</samp>’, ‘<samp>z9-109</samp>’,
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‘<samp>z9-ec</samp>’, ‘<samp>z10</samp>’, ‘<samp>z196</samp>’, ‘<samp>zEC12</samp>’, and ‘<samp>z13</samp>’.
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The default is <samp>-march=z900</samp>. ‘<samp>g5</samp>’ and ‘<samp>g6</samp>’ are
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deprecated and will be removed with future releases.
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</p>
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</dd>
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<dt><code>-mtune=<var>cpu-type</var></code></dt>
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<dd><a name="index-mtune-11"></a>
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<p>Tune to <var>cpu-type</var> everything applicable about the generated code,
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except for the ABI and the set of available instructions.
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The list of <var>cpu-type</var> values is the same as for <samp>-march</samp>.
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The default is the value used for <samp>-march</samp>.
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</p>
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</dd>
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<dt><code>-mtpf-trace</code></dt>
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<dt><code>-mno-tpf-trace</code></dt>
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<dd><a name="index-mtpf_002dtrace"></a>
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<a name="index-mno_002dtpf_002dtrace"></a>
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<p>Generate code that adds (does not add) in TPF OS specific branches to trace
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routines in the operating system. This option is off by default, even
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when compiling for the TPF OS.
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</p>
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</dd>
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<dt><code>-mfused-madd</code></dt>
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<dt><code>-mno-fused-madd</code></dt>
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<dd><a name="index-mfused_002dmadd-3"></a>
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<a name="index-mno_002dfused_002dmadd-3"></a>
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<p>Generate code that uses (does not use) the floating-point multiply and
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accumulate instructions. These instructions are generated by default if
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hardware floating point is used.
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</p>
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</dd>
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<dt><code>-mwarn-framesize=<var>framesize</var></code></dt>
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<dd><a name="index-mwarn_002dframesize"></a>
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<p>Emit a warning if the current function exceeds the given frame size. Because
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this is a compile-time check it doesn’t need to be a real problem when the program
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runs. It is intended to identify functions that most probably cause
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a stack overflow. It is useful to be used in an environment with limited stack
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size e.g. the linux kernel.
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</p>
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</dd>
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<dt><code>-mwarn-dynamicstack</code></dt>
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<dd><a name="index-mwarn_002ddynamicstack"></a>
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<p>Emit a warning if the function calls <code>alloca</code> or uses dynamically-sized
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arrays. This is generally a bad idea with a limited stack size.
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</p>
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</dd>
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<dt><code>-mstack-guard=<var>stack-guard</var></code></dt>
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<dt><code>-mstack-size=<var>stack-size</var></code></dt>
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<dd><a name="index-mstack_002dguard"></a>
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<a name="index-mstack_002dsize"></a>
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<p>If these options are provided the S/390 back end emits additional instructions in
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the function prologue that trigger a trap if the stack size is <var>stack-guard</var>
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bytes above the <var>stack-size</var> (remember that the stack on S/390 grows downward).
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If the <var>stack-guard</var> option is omitted the smallest power of 2 larger than
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the frame size of the compiled function is chosen.
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These options are intended to be used to help debugging stack overflow problems.
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The additionally emitted code causes only little overhead and hence can also be
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used in production-like systems without greater performance degradation. The given
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values have to be exact powers of 2 and <var>stack-size</var> has to be greater than
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<var>stack-guard</var> without exceeding 64k.
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In order to be efficient the extra code makes the assumption that the stack starts
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at an address aligned to the value given by <var>stack-size</var>.
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The <var>stack-guard</var> option can only be used in conjunction with <var>stack-size</var>.
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</p>
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</dd>
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<dt><code>-mhotpatch=<var>pre-halfwords</var>,<var>post-halfwords</var></code></dt>
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<dd><a name="index-mhotpatch"></a>
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<p>If the hotpatch option is enabled, a “hot-patching” function
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prologue is generated for all functions in the compilation unit.
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The funtion label is prepended with the given number of two-byte
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NOP instructions (<var>pre-halfwords</var>, maximum 1000000). After
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the label, 2 * <var>post-halfwords</var> bytes are appended, using the
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largest NOP like instructions the architecture allows (maximum
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1000000).
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</p>
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<p>If both arguments are zero, hotpatching is disabled.
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</p>
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<p>This option can be overridden for individual functions with the
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<code>hotpatch</code> attribute.
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</p></dd>
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</dl>
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<hr>
|
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<div class="header">
|
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<p>
|
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Next: <a href="Score-Options.html#Score-Options" accesskey="n" rel="next">Score Options</a>, Previous: <a href="RX-Options.html#RX-Options" accesskey="p" rel="prev">RX 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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</body>
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</html>
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