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| <a name="Machine_002dIndependent-Predicates"></a> |
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| 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> |
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| <a name="Machine_002dIndependent-Predicates-1"></a> |
| <h4 class="subsection">16.7.1 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> |
| |
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