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Copies published by the Free Software Foundation raise funds for GNU development. --> <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Machine-Independent Predicates (GNU Compiler Collection (GCC) Internals)</title> <meta name="description" content="Machine-Independent Predicates (GNU Compiler Collection (GCC) Internals)"> <meta name="keywords" content="Machine-Independent Predicates (GNU Compiler Collection (GCC) Internals)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <link href="index.html#Top" rel="start" title="Top"> <link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="Predicates.html#Predicates" rel="up" title="Predicates"> <link href="Defining-Predicates.html#Defining-Predicates" rel="next" title="Defining Predicates"> <link href="Predicates.html#Predicates" rel="prev" title="Predicates"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} div.smalllisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} pre.smalldisplay {font-family: inherit; font-size: smaller} pre.smallexample {font-size: smaller} pre.smallformat {font-family: inherit; font-size: smaller} pre.smalllisp {font-size: smaller} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <a name="Machine_002dIndependent-Predicates"></a> <div class="header"> <p> Next: <a href="Defining-Predicates.html#Defining-Predicates" accesskey="n" rel="next">Defining Predicates</a>, Up: <a href="Predicates.html#Predicates" accesskey="u" rel="up">Predicates</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> </div> <hr> <a name="Machine_002dIndependent-Predicates-1"></a> <h4 class="subsection">17.7.1 Machine-Independent Predicates</h4> <a name="index-machine_002dindependent-predicates"></a> <a name="index-generic-predicates"></a> <p>These are the generic predicates available to all back ends. They are defined in <samp>recog.c</samp>. The first category of predicates allow only constant, or <em>immediate</em>, operands. </p> <dl> <dt><a name="index-immediate_005foperand"></a>Function: <strong>immediate_operand</strong></dt> <dd><p>This predicate allows any sort of constant that fits in <var>mode</var>. It is an appropriate choice for instructions that take operands that must be constant. </p></dd></dl> <dl> <dt><a name="index-const_005fint_005foperand"></a>Function: <strong>const_int_operand</strong></dt> <dd><p>This predicate allows any <code>CONST_INT</code> expression that fits in <var>mode</var>. It is an appropriate choice for an immediate operand that does not allow a symbol or label. </p></dd></dl> <dl> <dt><a name="index-const_005fdouble_005foperand"></a>Function: <strong>const_double_operand</strong></dt> <dd><p>This predicate accepts any <code>CONST_DOUBLE</code> expression that has exactly <var>mode</var>. If <var>mode</var> is <code>VOIDmode</code>, it will also accept <code>CONST_INT</code>. It is intended for immediate floating point constants. </p></dd></dl> <p>The second category of predicates allow only some kind of machine register. </p> <dl> <dt><a name="index-register_005foperand"></a>Function: <strong>register_operand</strong></dt> <dd><p>This predicate allows any <code>REG</code> or <code>SUBREG</code> expression that is valid for <var>mode</var>. It is often suitable for arithmetic instruction operands on a RISC machine. </p></dd></dl> <dl> <dt><a name="index-pmode_005fregister_005foperand"></a>Function: <strong>pmode_register_operand</strong></dt> <dd><p>This is a slight variant on <code>register_operand</code> which works around a limitation in the machine-description reader. </p> <div class="smallexample"> <pre class="smallexample">(match_operand <var>n</var> "pmode_register_operand" <var>constraint</var>) </pre></div> <p>means exactly what </p> <div class="smallexample"> <pre class="smallexample">(match_operand:P <var>n</var> "register_operand" <var>constraint</var>) </pre></div> <p>would mean, if the machine-description reader accepted ‘<samp>:P</samp>’ mode suffixes. Unfortunately, it cannot, because <code>Pmode</code> is an alias for some other mode, and might vary with machine-specific options. See <a href="Misc.html#Misc">Misc</a>. </p></dd></dl> <dl> <dt><a name="index-scratch_005foperand"></a>Function: <strong>scratch_operand</strong></dt> <dd><p>This predicate allows hard registers and <code>SCRATCH</code> expressions, but not pseudo-registers. It is used internally by <code>match_scratch</code>; it should not be used directly. </p></dd></dl> <p>The third category of predicates allow only some kind of memory reference. </p> <dl> <dt><a name="index-memory_005foperand"></a>Function: <strong>memory_operand</strong></dt> <dd><p>This predicate allows any valid reference to a quantity of mode <var>mode</var> in memory, as determined by the weak form of <code>GO_IF_LEGITIMATE_ADDRESS</code> (see <a href="Addressing-Modes.html#Addressing-Modes">Addressing Modes</a>). </p></dd></dl> <dl> <dt><a name="index-address_005foperand"></a>Function: <strong>address_operand</strong></dt> <dd><p>This predicate is a little unusual; it allows any operand that is a valid expression for the <em>address</em> of a quantity of mode <var>mode</var>, again determined by the weak form of <code>GO_IF_LEGITIMATE_ADDRESS</code>. To first order, if ‘<samp>(mem:<var>mode</var> (<var>exp</var>))<!-- /@w --></samp>’ is acceptable to <code>memory_operand</code>, then <var>exp</var> is acceptable to <code>address_operand</code>. Note that <var>exp</var> does not necessarily have the mode <var>mode</var>. </p></dd></dl> <dl> <dt><a name="index-indirect_005foperand"></a>Function: <strong>indirect_operand</strong></dt> <dd><p>This is a stricter form of <code>memory_operand</code> which allows only memory references with a <code>general_operand</code> as the address expression. New uses of this predicate are discouraged, because <code>general_operand</code> is very permissive, so it’s hard to tell what an <code>indirect_operand</code> does or does not allow. If a target has different requirements for memory operands for different instructions, it is better to define target-specific predicates which enforce the hardware’s requirements explicitly. </p></dd></dl> <dl> <dt><a name="index-push_005foperand"></a>Function: <strong>push_operand</strong></dt> <dd><p>This predicate allows a memory reference suitable for pushing a value onto the stack. This will be a <code>MEM</code> which refers to <code>stack_pointer_rtx</code>, with a side effect in its address expression (see <a href="Incdec.html#Incdec">Incdec</a>); which one is determined by the <code>STACK_PUSH_CODE</code> macro (see <a href="Frame-Layout.html#Frame-Layout">Frame Layout</a>). </p></dd></dl> <dl> <dt><a name="index-pop_005foperand"></a>Function: <strong>pop_operand</strong></dt> <dd><p>This predicate allows a memory reference suitable for popping a value off the stack. Again, this will be a <code>MEM</code> referring to <code>stack_pointer_rtx</code>, with a side effect in its address expression. However, this time <code>STACK_POP_CODE</code> is expected. </p></dd></dl> <p>The fourth category of predicates allow some combination of the above operands. </p> <dl> <dt><a name="index-nonmemory_005foperand"></a>Function: <strong>nonmemory_operand</strong></dt> <dd><p>This predicate allows any immediate or register operand valid for <var>mode</var>. </p></dd></dl> <dl> <dt><a name="index-nonimmediate_005foperand"></a>Function: <strong>nonimmediate_operand</strong></dt> <dd><p>This predicate allows any register or memory operand valid for <var>mode</var>. </p></dd></dl> <dl> <dt><a name="index-general_005foperand"></a>Function: <strong>general_operand</strong></dt> <dd><p>This predicate allows any immediate, register, or memory operand valid for <var>mode</var>. </p></dd></dl> <p>Finally, there are two generic operator predicates. </p> <dl> <dt><a name="index-comparison_005foperator"></a>Function: <strong>comparison_operator</strong></dt> <dd><p>This predicate matches any expression which performs an arithmetic comparison in <var>mode</var>; that is, <code>COMPARISON_P</code> is true for the expression code. </p></dd></dl> <dl> <dt><a name="index-ordered_005fcomparison_005foperator"></a>Function: <strong>ordered_comparison_operator</strong></dt> <dd><p>This predicate matches any expression which performs an arithmetic comparison in <var>mode</var> and whose expression code is valid for integer modes; that is, the expression code will be one of <code>eq</code>, <code>ne</code>, <code>lt</code>, <code>ltu</code>, <code>le</code>, <code>leu</code>, <code>gt</code>, <code>gtu</code>, <code>ge</code>, <code>geu</code>. </p></dd></dl> <hr> <div class="header"> <p> Next: <a href="Defining-Predicates.html#Defining-Predicates" accesskey="n" rel="next">Defining Predicates</a>, Up: <a href="Predicates.html#Predicates" accesskey="u" rel="up">Predicates</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> </div> </body> </html>