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458 lines
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HTML
458 lines
30 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>SH Options - Using the GNU Compiler Collection (GCC)</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<meta name="generator" content="makeinfo 4.13">
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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="Score-Options.html#Score-Options" title="Score Options">
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<link rel="next" href="Solaris-2-Options.html#Solaris-2-Options" title="Solaris 2 Options">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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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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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.-->
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<meta http-equiv="Content-Style-Type" content="text/css">
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<style type="text/css"><!--
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pre.display { font-family:inherit }
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span.roman { font-family:serif; font-weight:normal; }
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span.sansserif { font-family:sans-serif; font-weight:normal; }
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="SH-Options"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Solaris-2-Options.html#Solaris-2-Options">Solaris 2 Options</a>,
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Previous: <a rel="previous" accesskey="p" href="Score-Options.html#Score-Options">Score 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">3.17.41 SH Options</h4>
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<p>These ‘<samp><span class="samp">-m</span></samp>’ options are defined for the SH implementations:
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<dl>
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<dt><code>-m1</code><dd><a name="index-m1-2433"></a>Generate code for the SH1.
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<br><dt><code>-m2</code><dd><a name="index-m2-2434"></a>Generate code for the SH2.
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<br><dt><code>-m2e</code><dd>Generate code for the SH2e.
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<br><dt><code>-m2a-nofpu</code><dd><a name="index-m2a_002dnofpu-2435"></a>Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way
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that the floating-point unit is not used.
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<br><dt><code>-m2a-single-only</code><dd><a name="index-m2a_002dsingle_002donly-2436"></a>Generate code for the SH2a-FPU, in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m2a-single</code><dd><a name="index-m2a_002dsingle-2437"></a>Generate code for the SH2a-FPU assuming the floating-point unit is in
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single-precision mode by default.
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<br><dt><code>-m2a</code><dd><a name="index-m2a-2438"></a>Generate code for the SH2a-FPU assuming the floating-point unit is in
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double-precision mode by default.
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<br><dt><code>-m3</code><dd><a name="index-m3-2439"></a>Generate code for the SH3.
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<br><dt><code>-m3e</code><dd><a name="index-m3e-2440"></a>Generate code for the SH3e.
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<br><dt><code>-m4-nofpu</code><dd><a name="index-m4_002dnofpu-2441"></a>Generate code for the SH4 without a floating-point unit.
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<br><dt><code>-m4-single-only</code><dd><a name="index-m4_002dsingle_002donly-2442"></a>Generate code for the SH4 with a floating-point unit that only
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supports single-precision arithmetic.
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<br><dt><code>-m4-single</code><dd><a name="index-m4_002dsingle-2443"></a>Generate code for the SH4 assuming the floating-point unit is in
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single-precision mode by default.
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<br><dt><code>-m4</code><dd><a name="index-m4-2444"></a>Generate code for the SH4.
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<br><dt><code>-m4-100</code><dd><a name="index-m4_002d100-2445"></a>Generate code for SH4-100.
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<br><dt><code>-m4-100-nofpu</code><dd><a name="index-m4_002d100_002dnofpu-2446"></a>Generate code for SH4-100 in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m4-100-single</code><dd><a name="index-m4_002d100_002dsingle-2447"></a>Generate code for SH4-100 assuming the floating-point unit is in
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single-precision mode by default.
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<br><dt><code>-m4-100-single-only</code><dd><a name="index-m4_002d100_002dsingle_002donly-2448"></a>Generate code for SH4-100 in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m4-200</code><dd><a name="index-m4_002d200-2449"></a>Generate code for SH4-200.
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<br><dt><code>-m4-200-nofpu</code><dd><a name="index-m4_002d200_002dnofpu-2450"></a>Generate code for SH4-200 without in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m4-200-single</code><dd><a name="index-m4_002d200_002dsingle-2451"></a>Generate code for SH4-200 assuming the floating-point unit is in
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single-precision mode by default.
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<br><dt><code>-m4-200-single-only</code><dd><a name="index-m4_002d200_002dsingle_002donly-2452"></a>Generate code for SH4-200 in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m4-300</code><dd><a name="index-m4_002d300-2453"></a>Generate code for SH4-300.
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<br><dt><code>-m4-300-nofpu</code><dd><a name="index-m4_002d300_002dnofpu-2454"></a>Generate code for SH4-300 without in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m4-300-single</code><dd><a name="index-m4_002d300_002dsingle-2455"></a>Generate code for SH4-300 in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m4-300-single-only</code><dd><a name="index-m4_002d300_002dsingle_002donly-2456"></a>Generate code for SH4-300 in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m4-340</code><dd><a name="index-m4_002d340-2457"></a>Generate code for SH4-340 (no MMU, no FPU).
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<br><dt><code>-m4-500</code><dd><a name="index-m4_002d500-2458"></a>Generate code for SH4-500 (no FPU). Passes <samp><span class="option">-isa=sh4-nofpu</span></samp> to the
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assembler.
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<br><dt><code>-m4a-nofpu</code><dd><a name="index-m4a_002dnofpu-2459"></a>Generate code for the SH4al-dsp, or for a SH4a in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m4a-single-only</code><dd><a name="index-m4a_002dsingle_002donly-2460"></a>Generate code for the SH4a, in such a way that no double-precision
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floating-point operations are used.
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<br><dt><code>-m4a-single</code><dd><a name="index-m4a_002dsingle-2461"></a>Generate code for the SH4a assuming the floating-point unit is in
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single-precision mode by default.
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<br><dt><code>-m4a</code><dd><a name="index-m4a-2462"></a>Generate code for the SH4a.
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<br><dt><code>-m4al</code><dd><a name="index-m4al-2463"></a>Same as <samp><span class="option">-m4a-nofpu</span></samp>, except that it implicitly passes
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<samp><span class="option">-dsp</span></samp> to the assembler. GCC doesn't generate any DSP
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instructions at the moment.
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<br><dt><code>-m5-32media</code><dd><a name="index-m5_002d32media-2464"></a>Generate 32-bit code for SHmedia.
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<br><dt><code>-m5-32media-nofpu</code><dd><a name="index-m5_002d32media_002dnofpu-2465"></a>Generate 32-bit code for SHmedia in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m5-64media</code><dd><a name="index-m5_002d64media-2466"></a>Generate 64-bit code for SHmedia.
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<br><dt><code>-m5-64media-nofpu</code><dd><a name="index-m5_002d64media_002dnofpu-2467"></a>Generate 64-bit code for SHmedia in such a way that the
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floating-point unit is not used.
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<br><dt><code>-m5-compact</code><dd><a name="index-m5_002dcompact-2468"></a>Generate code for SHcompact.
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<br><dt><code>-m5-compact-nofpu</code><dd><a name="index-m5_002dcompact_002dnofpu-2469"></a>Generate code for SHcompact in such a way that the
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floating-point unit is not used.
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<br><dt><code>-mb</code><dd><a name="index-mb-2470"></a>Compile code for the processor in big-endian mode.
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<br><dt><code>-ml</code><dd><a name="index-ml-2471"></a>Compile code for the processor in little-endian mode.
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<br><dt><code>-mdalign</code><dd><a name="index-mdalign-2472"></a>Align doubles at 64-bit boundaries. Note that this changes the calling
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conventions, and thus some functions from the standard C library do
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not work unless you recompile it first with <samp><span class="option">-mdalign</span></samp>.
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<br><dt><code>-mrelax</code><dd><a name="index-mrelax-2473"></a>Shorten some address references at link time, when possible; uses the
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linker option <samp><span class="option">-relax</span></samp>.
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<br><dt><code>-mbigtable</code><dd><a name="index-mbigtable-2474"></a>Use 32-bit offsets in <code>switch</code> tables. The default is to use
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16-bit offsets.
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<br><dt><code>-mbitops</code><dd><a name="index-mbitops-2475"></a>Enable the use of bit manipulation instructions on SH2A.
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<br><dt><code>-mfmovd</code><dd><a name="index-mfmovd-2476"></a>Enable the use of the instruction <code>fmovd</code>. Check <samp><span class="option">-mdalign</span></samp> for
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alignment constraints.
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<br><dt><code>-mrenesas</code><dd><a name="index-mrenesas-2477"></a>Comply with the calling conventions defined by Renesas.
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<br><dt><code>-mno-renesas</code><dd><a name="index-mno_002drenesas-2478"></a>Comply with the calling conventions defined for GCC before the Renesas
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conventions were available. This option is the default for all
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targets of the SH toolchain.
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<br><dt><code>-mnomacsave</code><dd><a name="index-mnomacsave-2479"></a>Mark the <code>MAC</code> register as call-clobbered, even if
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<samp><span class="option">-mrenesas</span></samp> is given.
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<br><dt><code>-mieee</code><dt><code>-mno-ieee</code><dd><a name="index-mieee-2480"></a><a name="index-mno_002dieee-2481"></a>Control the IEEE compliance of floating-point comparisons, which affects the
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handling of cases where the result of a comparison is unordered. By default
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<samp><span class="option">-mieee</span></samp> is implicitly enabled. If <samp><span class="option">-ffinite-math-only</span></samp> is
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enabled <samp><span class="option">-mno-ieee</span></samp> is implicitly set, which results in faster
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floating-point greater-equal and less-equal comparisons. The implcit settings
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can be overridden by specifying either <samp><span class="option">-mieee</span></samp> or <samp><span class="option">-mno-ieee</span></samp>.
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<br><dt><code>-minline-ic_invalidate</code><dd><a name="index-minline_002dic_005finvalidate-2482"></a>Inline code to invalidate instruction cache entries after setting up
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nested function trampolines.
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This option has no effect if <samp><span class="option">-musermode</span></samp> is in effect and the selected
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code generation option (e.g. <samp><span class="option">-m4</span></samp>) does not allow the use of the <code>icbi</code>
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instruction.
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If the selected code generation option does not allow the use of the <code>icbi</code>
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instruction, and <samp><span class="option">-musermode</span></samp> is not in effect, the inlined code
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manipulates the instruction cache address array directly with an associative
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write. This not only requires privileged mode at run time, but it also
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fails if the cache line had been mapped via the TLB and has become unmapped.
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<br><dt><code>-misize</code><dd><a name="index-misize-2483"></a>Dump instruction size and location in the assembly code.
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<br><dt><code>-mpadstruct</code><dd><a name="index-mpadstruct-2484"></a>This option is deprecated. It pads structures to multiple of 4 bytes,
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which is incompatible with the SH ABI.
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<br><dt><code>-matomic-model=</code><var>model</var><dd><a name="index-matomic_002dmodel_003d_0040var_007bmodel_007d-2485"></a>Sets the model of atomic operations and additional parameters as a comma
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separated list. For details on the atomic built-in functions see
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<a href="_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins">__atomic Builtins</a>. The following models and parameters are supported:
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<dl>
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<dt>‘<samp><span class="samp">none</span></samp>’<dd>Disable compiler generated atomic sequences and emit library calls for atomic
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operations. This is the default if the target is not <code>sh*-*-linux*</code>.
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<br><dt>‘<samp><span class="samp">soft-gusa</span></samp>’<dd>Generate GNU/Linux compatible gUSA software atomic sequences for the atomic
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built-in functions. The generated atomic sequences require additional support
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from the interrupt/exception handling code of the system and are only suitable
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for SH3* and SH4* single-core systems. This option is enabled by default when
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the target is <code>sh*-*-linux*</code> and SH3* or SH4*. When the target is SH4A,
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this option also partially utilizes the hardware atomic instructions
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<code>movli.l</code> and <code>movco.l</code> to create more efficient code, unless
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‘<samp><span class="samp">strict</span></samp>’ is specified.
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<br><dt>‘<samp><span class="samp">soft-tcb</span></samp>’<dd>Generate software atomic sequences that use a variable in the thread control
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block. This is a variation of the gUSA sequences which can also be used on
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SH1* and SH2* targets. The generated atomic sequences require additional
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support from the interrupt/exception handling code of the system and are only
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suitable for single-core systems. When using this model, the ‘<samp><span class="samp">gbr-offset=</span></samp>’
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parameter has to be specified as well.
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<br><dt>‘<samp><span class="samp">soft-imask</span></samp>’<dd>Generate software atomic sequences that temporarily disable interrupts by
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setting <code>SR.IMASK = 1111</code>. This model works only when the program runs
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in privileged mode and is only suitable for single-core systems. Additional
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support from the interrupt/exception handling code of the system is not
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required. This model is enabled by default when the target is
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<code>sh*-*-linux*</code> and SH1* or SH2*.
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<br><dt>‘<samp><span class="samp">hard-llcs</span></samp>’<dd>Generate hardware atomic sequences using the <code>movli.l</code> and <code>movco.l</code>
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instructions only. This is only available on SH4A and is suitable for
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multi-core systems. Since the hardware instructions support only 32 bit atomic
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variables access to 8 or 16 bit variables is emulated with 32 bit accesses.
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Code compiled with this option is also compatible with other software
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atomic model interrupt/exception handling systems if executed on an SH4A
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system. Additional support from the interrupt/exception handling code of the
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system is not required for this model.
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|
<br><dt>‘<samp><span class="samp">gbr-offset=</span></samp>’<dd>This parameter specifies the offset in bytes of the variable in the thread
|
||
|
|
control block structure that should be used by the generated atomic sequences
|
||
|
|
when the ‘<samp><span class="samp">soft-tcb</span></samp>’ model has been selected. For other models this
|
||
|
|
parameter is ignored. The specified value must be an integer multiple of four
|
||
|
|
and in the range 0-1020.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">strict</span></samp>’<dd>This parameter prevents mixed usage of multiple atomic models, even if they
|
||
|
|
are compatible, and makes the compiler generate atomic sequences of the
|
||
|
|
specified model only.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<br><dt><code>-mtas</code><dd><a name="index-mtas-2486"></a>Generate the <code>tas.b</code> opcode for <code>__atomic_test_and_set</code>.
|
||
|
|
Notice that depending on the particular hardware and software configuration
|
||
|
|
this can degrade overall performance due to the operand cache line flushes
|
||
|
|
that are implied by the <code>tas.b</code> instruction. On multi-core SH4A
|
||
|
|
processors the <code>tas.b</code> instruction must be used with caution since it
|
||
|
|
can result in data corruption for certain cache configurations.
|
||
|
|
|
||
|
|
<br><dt><code>-mprefergot</code><dd><a name="index-mprefergot-2487"></a>When generating position-independent code, emit function calls using
|
||
|
|
the Global Offset Table instead of the Procedure Linkage Table.
|
||
|
|
|
||
|
|
<br><dt><code>-musermode</code><dt><code>-mno-usermode</code><dd><a name="index-musermode-2488"></a><a name="index-mno_002dusermode-2489"></a>Don't allow (allow) the compiler generating privileged mode code. Specifying
|
||
|
|
<samp><span class="option">-musermode</span></samp> also implies <samp><span class="option">-mno-inline-ic_invalidate</span></samp> if the
|
||
|
|
inlined code would not work in user mode. <samp><span class="option">-musermode</span></samp> is the default
|
||
|
|
when the target is <code>sh*-*-linux*</code>. If the target is SH1* or SH2*
|
||
|
|
<samp><span class="option">-musermode</span></samp> has no effect, since there is no user mode.
|
||
|
|
|
||
|
|
<br><dt><code>-multcost=</code><var>number</var><dd><a name="index-multcost_003d_0040var_007bnumber_007d-2490"></a>Set the cost to assume for a multiply insn.
|
||
|
|
|
||
|
|
<br><dt><code>-mdiv=</code><var>strategy</var><dd><a name="index-mdiv_003d_0040var_007bstrategy_007d-2491"></a>Set the division strategy to be used for integer division operations.
|
||
|
|
For SHmedia <var>strategy</var> can be one of:
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt>‘<samp><span class="samp">fp</span></samp>’<dd>Performs the operation in floating point. This has a very high latency,
|
||
|
|
but needs only a few instructions, so it might be a good choice if
|
||
|
|
your code has enough easily-exploitable ILP to allow the compiler to
|
||
|
|
schedule the floating-point instructions together with other instructions.
|
||
|
|
Division by zero causes a floating-point exception.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">inv</span></samp>’<dd>Uses integer operations to calculate the inverse of the divisor,
|
||
|
|
and then multiplies the dividend with the inverse. This strategy allows
|
||
|
|
CSE and hoisting of the inverse calculation. Division by zero calculates
|
||
|
|
an unspecified result, but does not trap.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">inv:minlat</span></samp>’<dd>A variant of ‘<samp><span class="samp">inv</span></samp>’ where, if no CSE or hoisting opportunities
|
||
|
|
have been found, or if the entire operation has been hoisted to the same
|
||
|
|
place, the last stages of the inverse calculation are intertwined with the
|
||
|
|
final multiply to reduce the overall latency, at the expense of using a few
|
||
|
|
more instructions, and thus offering fewer scheduling opportunities with
|
||
|
|
other code.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">call</span></samp>’<dd>Calls a library function that usually implements the ‘<samp><span class="samp">inv:minlat</span></samp>’
|
||
|
|
strategy.
|
||
|
|
This gives high code density for <code>m5-*media-nofpu</code> compilations.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">call2</span></samp>’<dd>Uses a different entry point of the same library function, where it
|
||
|
|
assumes that a pointer to a lookup table has already been set up, which
|
||
|
|
exposes the pointer load to CSE and code hoisting optimizations.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">inv:call</span></samp>’<dt>‘<samp><span class="samp">inv:call2</span></samp>’<dt>‘<samp><span class="samp">inv:fp</span></samp>’<dd>Use the ‘<samp><span class="samp">inv</span></samp>’ algorithm for initial
|
||
|
|
code generation, but if the code stays unoptimized, revert to the ‘<samp><span class="samp">call</span></samp>’,
|
||
|
|
‘<samp><span class="samp">call2</span></samp>’, or ‘<samp><span class="samp">fp</span></samp>’ strategies, respectively. Note that the
|
||
|
|
potentially-trapping side effect of division by zero is carried by a
|
||
|
|
separate instruction, so it is possible that all the integer instructions
|
||
|
|
are hoisted out, but the marker for the side effect stays where it is.
|
||
|
|
A recombination to floating-point operations or a call is not possible
|
||
|
|
in that case.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">inv20u</span></samp>’<dt>‘<samp><span class="samp">inv20l</span></samp>’<dd>Variants of the ‘<samp><span class="samp">inv:minlat</span></samp>’ strategy. In the case
|
||
|
|
that the inverse calculation is not separated from the multiply, they speed
|
||
|
|
up division where the dividend fits into 20 bits (plus sign where applicable)
|
||
|
|
by inserting a test to skip a number of operations in this case; this test
|
||
|
|
slows down the case of larger dividends. ‘<samp><span class="samp">inv20u</span></samp>’ assumes the case of a such
|
||
|
|
a small dividend to be unlikely, and ‘<samp><span class="samp">inv20l</span></samp>’ assumes it to be likely.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>For targets other than SHmedia <var>strategy</var> can be one of:
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt>‘<samp><span class="samp">call-div1</span></samp>’<dd>Calls a library function that uses the single-step division instruction
|
||
|
|
<code>div1</code> to perform the operation. Division by zero calculates an
|
||
|
|
unspecified result and does not trap. This is the default except for SH4,
|
||
|
|
SH2A and SHcompact.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">call-fp</span></samp>’<dd>Calls a library function that performs the operation in double precision
|
||
|
|
floating point. Division by zero causes a floating-point exception. This is
|
||
|
|
the default for SHcompact with FPU. Specifying this for targets that do not
|
||
|
|
have a double precision FPU defaults to <code>call-div1</code>.
|
||
|
|
|
||
|
|
<br><dt>‘<samp><span class="samp">call-table</span></samp>’<dd>Calls a library function that uses a lookup table for small divisors and
|
||
|
|
the <code>div1</code> instruction with case distinction for larger divisors. Division
|
||
|
|
by zero calculates an unspecified result and does not trap. This is the default
|
||
|
|
for SH4. Specifying this for targets that do not have dynamic shift
|
||
|
|
instructions defaults to <code>call-div1</code>.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>When a division strategy has not been specified the default strategy is
|
||
|
|
selected based on the current target. For SH2A the default strategy is to
|
||
|
|
use the <code>divs</code> and <code>divu</code> instructions instead of library function
|
||
|
|
calls.
|
||
|
|
|
||
|
|
<br><dt><code>-maccumulate-outgoing-args</code><dd><a name="index-maccumulate_002doutgoing_002dargs-2492"></a>Reserve space once for outgoing arguments in the function prologue rather
|
||
|
|
than around each call. Generally beneficial for performance and size. Also
|
||
|
|
needed for unwinding to avoid changing the stack frame around conditional code.
|
||
|
|
|
||
|
|
<br><dt><code>-mdivsi3_libfunc=</code><var>name</var><dd><a name="index-mdivsi3_005flibfunc_003d_0040var_007bname_007d-2493"></a>Set the name of the library function used for 32-bit signed division to
|
||
|
|
<var>name</var>.
|
||
|
|
This only affects the name used in the ‘<samp><span class="samp">call</span></samp>’ and ‘<samp><span class="samp">inv:call</span></samp>’
|
||
|
|
division strategies, and the compiler still expects the same
|
||
|
|
sets of input/output/clobbered registers as if this option were not present.
|
||
|
|
|
||
|
|
<br><dt><code>-mfixed-range=</code><var>register-range</var><dd><a name="index-mfixed_002drange-2494"></a>Generate code treating the given register range as fixed registers.
|
||
|
|
A fixed register is one that the register allocator can not use. This is
|
||
|
|
useful when compiling kernel code. A register range is specified as
|
||
|
|
two registers separated by a dash. Multiple register ranges can be
|
||
|
|
specified separated by a comma.
|
||
|
|
|
||
|
|
<br><dt><code>-mindexed-addressing</code><dd><a name="index-mindexed_002daddressing-2495"></a>Enable the use of the indexed addressing mode for SHmedia32/SHcompact.
|
||
|
|
This is only safe if the hardware and/or OS implement 32-bit wrap-around
|
||
|
|
semantics for the indexed addressing mode. The architecture allows the
|
||
|
|
implementation of processors with 64-bit MMU, which the OS could use to
|
||
|
|
get 32-bit addressing, but since no current hardware implementation supports
|
||
|
|
this or any other way to make the indexed addressing mode safe to use in
|
||
|
|
the 32-bit ABI, the default is <samp><span class="option">-mno-indexed-addressing</span></samp>.
|
||
|
|
|
||
|
|
<br><dt><code>-mgettrcost=</code><var>number</var><dd><a name="index-mgettrcost_003d_0040var_007bnumber_007d-2496"></a>Set the cost assumed for the <code>gettr</code> instruction to <var>number</var>.
|
||
|
|
The default is 2 if <samp><span class="option">-mpt-fixed</span></samp> is in effect, 100 otherwise.
|
||
|
|
|
||
|
|
<br><dt><code>-mpt-fixed</code><dd><a name="index-mpt_002dfixed-2497"></a>Assume <code>pt*</code> instructions won't trap. This generally generates
|
||
|
|
better-scheduled code, but is unsafe on current hardware.
|
||
|
|
The current architecture
|
||
|
|
definition says that <code>ptabs</code> and <code>ptrel</code> trap when the target
|
||
|
|
anded with 3 is 3.
|
||
|
|
This has the unintentional effect of making it unsafe to schedule these
|
||
|
|
instructions before a branch, or hoist them out of a loop. For example,
|
||
|
|
<code>__do_global_ctors</code>, a part of <samp><span class="file">libgcc</span></samp>
|
||
|
|
that runs constructors at program
|
||
|
|
startup, calls functions in a list which is delimited by −1. With the
|
||
|
|
<samp><span class="option">-mpt-fixed</span></samp> option, the <code>ptabs</code> is done before testing against −1.
|
||
|
|
That means that all the constructors run a bit more quickly, but when
|
||
|
|
the loop comes to the end of the list, the program crashes because <code>ptabs</code>
|
||
|
|
loads −1 into a target register.
|
||
|
|
|
||
|
|
<p>Since this option is unsafe for any
|
||
|
|
hardware implementing the current architecture specification, the default
|
||
|
|
is <samp><span class="option">-mno-pt-fixed</span></samp>. Unless specified explicitly with
|
||
|
|
<samp><span class="option">-mgettrcost</span></samp>, <samp><span class="option">-mno-pt-fixed</span></samp> also implies <samp><span class="option">-mgettrcost=100</span></samp>;
|
||
|
|
this deters register allocation from using target registers for storing
|
||
|
|
ordinary integers.
|
||
|
|
|
||
|
|
<br><dt><code>-minvalid-symbols</code><dd><a name="index-minvalid_002dsymbols-2498"></a>Assume symbols might be invalid. Ordinary function symbols generated by
|
||
|
|
the compiler are always valid to load with
|
||
|
|
<code>movi</code>/<code>shori</code>/<code>ptabs</code> or
|
||
|
|
<code>movi</code>/<code>shori</code>/<code>ptrel</code>,
|
||
|
|
but with assembler and/or linker tricks it is possible
|
||
|
|
to generate symbols that cause <code>ptabs</code> or <code>ptrel</code> to trap.
|
||
|
|
This option is only meaningful when <samp><span class="option">-mno-pt-fixed</span></samp> is in effect.
|
||
|
|
It prevents cross-basic-block CSE, hoisting and most scheduling
|
||
|
|
of symbol loads. The default is <samp><span class="option">-mno-invalid-symbols</span></samp>.
|
||
|
|
|
||
|
|
<br><dt><code>-mbranch-cost=</code><var>num</var><dd><a name="index-mbranch_002dcost_003d_0040var_007bnum_007d-2499"></a>Assume <var>num</var> to be the cost for a branch instruction. Higher numbers
|
||
|
|
make the compiler try to generate more branch-free code if possible.
|
||
|
|
If not specified the value is selected depending on the processor type that
|
||
|
|
is being compiled for.
|
||
|
|
|
||
|
|
<br><dt><code>-mzdcbranch</code><dt><code>-mno-zdcbranch</code><dd><a name="index-mzdcbranch-2500"></a><a name="index-mno_002dzdcbranch-2501"></a>Assume (do not assume) that zero displacement conditional branch instructions
|
||
|
|
<code>bt</code> and <code>bf</code> are fast. If <samp><span class="option">-mzdcbranch</span></samp> is specified, the
|
||
|
|
compiler prefers zero displacement branch code sequences. This is
|
||
|
|
enabled by default when generating code for SH4 and SH4A. It can be explicitly
|
||
|
|
disabled by specifying <samp><span class="option">-mno-zdcbranch</span></samp>.
|
||
|
|
|
||
|
|
<br><dt><code>-mcbranch-force-delay-slot</code><dd><a name="index-mcbranch_002dforce_002ddelay_002dslot-2502"></a>Force the usage of delay slots for conditional branches, which stuffs the delay
|
||
|
|
slot with a <code>nop</code> if a suitable instruction can't be found. By default
|
||
|
|
this option is disabled. It can be enabled to work around hardware bugs as
|
||
|
|
found in the original SH7055.
|
||
|
|
|
||
|
|
<br><dt><code>-mfused-madd</code><dt><code>-mno-fused-madd</code><dd><a name="index-mfused_002dmadd-2503"></a><a name="index-mno_002dfused_002dmadd-2504"></a>Generate code that uses (does not use) the floating-point multiply and
|
||
|
|
accumulate instructions. These instructions are generated by default
|
||
|
|
if hardware floating point is used. The machine-dependent
|
||
|
|
<samp><span class="option">-mfused-madd</span></samp> option is now mapped to the machine-independent
|
||
|
|
<samp><span class="option">-ffp-contract=fast</span></samp> option, and <samp><span class="option">-mno-fused-madd</span></samp> is
|
||
|
|
mapped to <samp><span class="option">-ffp-contract=off</span></samp>.
|
||
|
|
|
||
|
|
<br><dt><code>-mfsca</code><dt><code>-mno-fsca</code><dd><a name="index-mfsca-2505"></a><a name="index-mno_002dfsca-2506"></a>Allow or disallow the compiler to emit the <code>fsca</code> instruction for sine
|
||
|
|
and cosine approximations. The option <samp><span class="option">-mfsca</span></samp> must be used in
|
||
|
|
combination with <samp><span class="option">-funsafe-math-optimizations</span></samp>. It is enabled by default
|
||
|
|
when generating code for SH4A. Using <samp><span class="option">-mno-fsca</span></samp> disables sine and cosine
|
||
|
|
approximations even if <samp><span class="option">-funsafe-math-optimizations</span></samp> is in effect.
|
||
|
|
|
||
|
|
<br><dt><code>-mfsrra</code><dt><code>-mno-fsrra</code><dd><a name="index-mfsrra-2507"></a><a name="index-mno_002dfsrra-2508"></a>Allow or disallow the compiler to emit the <code>fsrra</code> instruction for
|
||
|
|
reciprocal square root approximations. The option <samp><span class="option">-mfsrra</span></samp> must be used
|
||
|
|
in combination with <samp><span class="option">-funsafe-math-optimizations</span></samp> and
|
||
|
|
<samp><span class="option">-ffinite-math-only</span></samp>. It is enabled by default when generating code for
|
||
|
|
SH4A. Using <samp><span class="option">-mno-fsrra</span></samp> disables reciprocal square root approximations
|
||
|
|
even if <samp><span class="option">-funsafe-math-optimizations</span></samp> and <samp><span class="option">-ffinite-math-only</span></samp> are
|
||
|
|
in effect.
|
||
|
|
|
||
|
|
<br><dt><code>-mpretend-cmove</code><dd><a name="index-mpretend_002dcmove-2509"></a>Prefer zero-displacement conditional branches for conditional move instruction
|
||
|
|
patterns. This can result in faster code on the SH4 processor.
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|