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210 lines
15 KiB
HTML
4 years ago
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<title>S/390 and zSeries Options - Using the GNU Compiler Collection (GCC)</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Submodel-Options.html#Submodel-Options" title="Submodel Options">
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<link rel="prev" href="RX-Options.html#RX-Options" title="RX Options">
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<link rel="next" href="Score-Options.html#Score-Options" title="Score Options">
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Funding Free Software'', the Front-Cover
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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<body>
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<div class="node">
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<a name="S%2f390-and-zSeries-Options"></a>
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<a name="S_002f390-and-zSeries-Options"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Score-Options.html#Score-Options">Score Options</a>,
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Previous: <a rel="previous" accesskey="p" href="RX-Options.html#RX-Options">RX Options</a>,
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Up: <a rel="up" accesskey="u" href="Submodel-Options.html#Submodel-Options">Submodel Options</a>
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<hr>
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</div>
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<h4 class="subsection">3.17.39 S/390 and zSeries Options</h4>
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<p><a name="index-S_002f390-and-zSeries-Options-2391"></a>
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These are the ‘<samp><span class="samp">-m</span></samp>’ options defined for the S/390 and zSeries architecture.
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<dl>
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<dt><code>-mhard-float</code><dt><code>-msoft-float</code><dd><a name="index-mhard_002dfloat-2392"></a><a name="index-msoft_002dfloat-2393"></a>Use (do not use) the hardware floating-point instructions and registers
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for floating-point operations. When <samp><span class="option">-msoft-float</span></samp> is specified,
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functions in <samp><span class="file">libgcc.a</span></samp> are used to perform floating-point
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operations. When <samp><span class="option">-mhard-float</span></samp> is specified, the compiler
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generates IEEE floating-point instructions. This is the default.
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<br><dt><code>-mhard-dfp</code><dt><code>-mno-hard-dfp</code><dd><a name="index-mhard_002ddfp-2394"></a><a name="index-mno_002dhard_002ddfp-2395"></a>Use (do not use) the hardware decimal-floating-point instructions for
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decimal-floating-point operations. When <samp><span class="option">-mno-hard-dfp</span></samp> is
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specified, functions in <samp><span class="file">libgcc.a</span></samp> are used to perform
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decimal-floating-point operations. When <samp><span class="option">-mhard-dfp</span></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><span class="option">-march=z9-ec</span></samp> or higher.
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<br><dt><code>-mlong-double-64</code><dt><code>-mlong-double-128</code><dd><a name="index-mlong_002ddouble_002d64-2396"></a><a name="index-mlong_002ddouble_002d128-2397"></a>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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<br><dt><code>-mbackchain</code><dt><code>-mno-backchain</code><dd><a name="index-mbackchain-2398"></a><a name="index-mno_002dbackchain-2399"></a>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 2 call frame information.
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When <samp><span class="option">-mno-packed-stack</span></samp> is in effect, the backchain pointer is stored
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at the bottom of the stack frame; when <samp><span class="option">-mpacked-stack</span></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>In general, code compiled with <samp><span class="option">-mbackchain</span></samp> is call-compatible with
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code compiled with <samp><span class="option">-mmo-backchain</span></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><span class="option">-mbackchain</span></samp>. Note that the combination of <samp><span class="option">-mbackchain</span></samp>,
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<samp><span class="option">-mpacked-stack</span></samp> and <samp><span class="option">-mhard-float</span></samp> is not supported. In order
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to build a linux kernel use <samp><span class="option">-msoft-float</span></samp>.
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<p>The default is to not maintain the backchain.
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<br><dt><code>-mpacked-stack</code><dt><code>-mno-packed-stack</code><dd><a name="index-mpacked_002dstack-2400"></a><a name="index-mno_002dpacked_002dstack-2401"></a>Use (do not use) the packed stack layout. When <samp><span class="option">-mno-packed-stack</span></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><span class="option">-mpacked-stack</span></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><span class="option">-mbackchain</span></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>As long as the stack frame backchain is not used, code generated with
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<samp><span class="option">-mpacked-stack</span></samp> is call-compatible with code generated with
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<samp><span class="option">-mno-packed-stack</span></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><span class="option">-mpacked-stack</span></samp>. Also, note that the
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combination of <samp><span class="option">-mbackchain</span></samp>,
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<samp><span class="option">-mpacked-stack</span></samp> and <samp><span class="option">-mhard-float</span></samp> is not supported. In order
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to build a linux kernel use <samp><span class="option">-msoft-float</span></samp>.
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<p>The default is to not use the packed stack layout.
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<br><dt><code>-msmall-exec</code><dt><code>-mno-small-exec</code><dd><a name="index-msmall_002dexec-2402"></a><a name="index-mno_002dsmall_002dexec-2403"></a>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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<br><dt><code>-m64</code><dt><code>-m31</code><dd><a name="index-m64-2404"></a><a name="index-m31-2405"></a>When <samp><span class="option">-m31</span></samp> is specified, generate code compliant to the
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GNU/Linux for S/390 ABI. When <samp><span class="option">-m64</span></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><span class="samp">s390</span></samp>’
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targets, the default is <samp><span class="option">-m31</span></samp>, while the ‘<samp><span class="samp">s390x</span></samp>’
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targets default to <samp><span class="option">-m64</span></samp>.
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<br><dt><code>-mzarch</code><dt><code>-mesa</code><dd><a name="index-mzarch-2406"></a><a name="index-mesa-2407"></a>When <samp><span class="option">-mzarch</span></samp> is specified, generate code using the
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instructions available on z/Architecture.
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When <samp><span class="option">-mesa</span></samp> is specified, generate code using the
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instructions available on ESA/390. Note that <samp><span class="option">-mesa</span></samp> is
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not possible with <samp><span class="option">-m64</span></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><span class="option">-mesa</span></samp>. When generating code compliant
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to the GNU/Linux for zSeries ABI, the default is <samp><span class="option">-mzarch</span></samp>.
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<br><dt><code>-mmvcle</code><dt><code>-mno-mvcle</code><dd><a name="index-mmvcle-2408"></a><a name="index-mno_002dmvcle-2409"></a>Generate (or do not generate) code using the <code>mvcle</code> instruction
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to perform block moves. When <samp><span class="option">-mno-mvcle</span></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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<br><dt><code>-mdebug</code><dt><code>-mno-debug</code><dd><a name="index-mdebug-2410"></a><a name="index-mno_002ddebug-2411"></a>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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<br><dt><code>-march=</code><var>cpu-type</var><dd><a name="index-march-2412"></a>Generate code that runs on <var>cpu-type</var>, which is the name of a system
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representing a certain processor type. Possible values for
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<var>cpu-type</var> are ‘<samp><span class="samp">g5</span></samp>’, ‘<samp><span class="samp">g6</span></samp>’, ‘<samp><span class="samp">z900</span></samp>’, ‘<samp><span class="samp">z990</span></samp>’,
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‘<samp><span class="samp">z9-109</span></samp>’, ‘<samp><span class="samp">z9-ec</span></samp>’, ‘<samp><span class="samp">z10</span></samp>’, ‘<samp><span class="samp">z196</span></samp>’, ‘<samp><span class="samp">zEC12</span></samp>’,
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and ‘<samp><span class="samp">z13</span></samp>’.
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When generating code using the instructions available on z/Architecture,
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the default is <samp><span class="option">-march=z900</span></samp>. Otherwise, the default is
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<samp><span class="option">-march=g5</span></samp>.
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<br><dt><code>-mtune=</code><var>cpu-type</var><dd><a name="index-mtune-2413"></a>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><span class="option">-march</span></samp>.
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The default is the value used for <samp><span class="option">-march</span></samp>.
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<br><dt><code>-mtpf-trace</code><dt><code>-mno-tpf-trace</code><dd><a name="index-mtpf_002dtrace-2414"></a><a name="index-mno_002dtpf_002dtrace-2415"></a>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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<br><dt><code>-mfused-madd</code><dt><code>-mno-fused-madd</code><dd><a name="index-mfused_002dmadd-2416"></a><a name="index-mno_002dfused_002dmadd-2417"></a>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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<br><dt><code>-mwarn-framesize=</code><var>framesize</var><dd><a name="index-mwarn_002dframesize-2418"></a>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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<br><dt><code>-mwarn-dynamicstack</code><dd><a name="index-mwarn_002ddynamicstack-2419"></a>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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<br><dt><code>-mstack-guard=</code><var>stack-guard</var><dt><code>-mstack-size=</code><var>stack-size</var><dd><a name="index-mstack_002dguard-2420"></a><a name="index-mstack_002dsize-2421"></a>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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<br><dt><code>-mhotpatch=</code><var>pre-halfwords</var><code>,</code><var>post-halfwords</var><dd><a name="index-mhotpatch-2422"></a>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>If both arguments are zero, hotpatching is disabled.
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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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</dl>
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</body></html>
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