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123 lines
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123 lines
5.4 KiB
HTML
4 years ago
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<html lang="en">
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<title>Int Iterators - GNU Compiler Collection (GCC) Internals</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Iterators.html#Iterators" title="Iterators">
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<link rel="prev" href="Code-Iterators.html#Code-Iterators" title="Code Iterators">
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<link rel="next" href="Subst-Iterators.html#Subst-Iterators" title="Subst Iterators">
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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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(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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</head>
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<body>
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<div class="node">
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<a name="Int-Iterators"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Subst-Iterators.html#Subst-Iterators">Subst Iterators</a>,
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Previous: <a rel="previous" accesskey="p" href="Code-Iterators.html#Code-Iterators">Code Iterators</a>,
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Up: <a rel="up" accesskey="u" href="Iterators.html#Iterators">Iterators</a>
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<hr>
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</div>
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<h4 class="subsection">16.23.3 Int Iterators</h4>
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<p><a name="index-int-iterators-in-_0040file_007b_002emd_007d-files-3843"></a><a name="index-define_005fint_005fiterator-3844"></a><a name="index-define_005fint_005fattr-3845"></a>
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Int iterators operate in a similar way to code iterators. See <a href="Code-Iterators.html#Code-Iterators">Code Iterators</a>.
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<p>The construct:
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<pre class="smallexample"> (define_int_iterator <var>name</var> [(<var>int1</var> "<var>cond1</var>") ... (<var>intn</var> "<var>condn</var>")])
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</pre>
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<p>defines a pseudo integer constant <var>name</var> that can be instantiated as
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<var>inti</var> if condition <var>condi</var> is true. Each <var>int</var>
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must have the same rtx format. See <a href="RTL-Classes.html#RTL-Classes">RTL Classes</a>. Int iterators can appear
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in only those rtx fields that have 'i' as the specifier. This means that
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each <var>int</var> has to be a constant defined using define_constant or
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define_c_enum.
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<p>As with mode and code iterators, each pattern that uses <var>name</var> will be
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expanded <var>n</var> times, once with all uses of <var>name</var> replaced by
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<var>int1</var>, once with all uses replaced by <var>int2</var>, and so on.
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See <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators">Defining Mode Iterators</a>.
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<p>It is possible to define attributes for ints as well as for codes and modes.
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Attributes are defined using:
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<pre class="smallexample"> (define_int_attr <var>name</var> [(<var>int1</var> "<var>value1</var>") ... (<var>intn</var> "<var>valuen</var>")])
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</pre>
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<p>Here's an example of int iterators in action, taken from the ARM port:
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<pre class="smallexample"> (define_int_iterator QABSNEG [UNSPEC_VQABS UNSPEC_VQNEG])
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(define_int_attr absneg [(UNSPEC_VQABS "abs") (UNSPEC_VQNEG "neg")])
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(define_insn "neon_vq<absneg><mode>"
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[(set (match_operand:VDQIW 0 "s_register_operand" "=w")
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(unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
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(match_operand:SI 2 "immediate_operand" "i")]
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QABSNEG))]
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"TARGET_NEON"
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"vq<absneg>.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
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[(set_attr "type" "neon_vqneg_vqabs")]
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)
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</pre>
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<p>This is equivalent to:
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<pre class="smallexample"> (define_insn "neon_vqabs<mode>"
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[(set (match_operand:VDQIW 0 "s_register_operand" "=w")
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(unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
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(match_operand:SI 2 "immediate_operand" "i")]
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UNSPEC_VQABS))]
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"TARGET_NEON"
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"vqabs.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
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[(set_attr "type" "neon_vqneg_vqabs")]
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)
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(define_insn "neon_vqneg<mode>"
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[(set (match_operand:VDQIW 0 "s_register_operand" "=w")
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(unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
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(match_operand:SI 2 "immediate_operand" "i")]
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UNSPEC_VQNEG))]
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"TARGET_NEON"
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"vqneg.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
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[(set_attr "type" "neon_vqneg_vqabs")]
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)
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</pre>
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</body></html>
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