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  25. <title>Converting poly_ints (GNU Compiler Collection (GCC) Internals)</title>

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  35. <link href="poly_005fint.html#poly_005fint" rel="up" title="poly_int">

  36. <link href="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" rel="next" title="Miscellaneous poly_int routines">

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  70. <a name="Converting-poly_005fints"></a>

  71. <div class="header">

  72. <p>

  73. Next: <a href="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" accesskey="n" rel="next">Miscellaneous <code>poly_int</code> routines</a>, Previous: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="p" rel="prev">Computing bounds on <code>poly_int</code>s</a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> &nbsp; [<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>

  74. </div>

  75. <hr>

  76. <a name="Converting-poly_005fints-1"></a>

  77. <h3 class="section">10.7 Converting <code>poly_int</code>s</h3>

  78. 

  79. <p>A <code>poly_int&lt;<var>n</var>, <var>T</var>&gt;</code> can be constructed from up to

  80. <var>n</var> individual <var>T</var> coefficients, with the remaining coefficients

  81. being implicitly zero.  In particular, this means that every

  82. <code>poly_int&lt;<var>n</var>, <var>T</var>&gt;</code> can be constructed from a single

  83. scalar <var>T</var>, or something compatible with <var>T</var>.

  84. </p>

  85. <p>Also, a <code>poly_int&lt;<var>n</var>, <var>T</var>&gt;</code> can be constructed from

  86. a <code>poly_int&lt;<var>n</var>, <var>U</var>&gt;</code> if <var>T</var> can be constructed

  87. from <var>U</var>.

  88. </p>

  89. <p>The following functions provide other forms of conversion,

  90. or test whether such a conversion would succeed.

  91. </p>

  92. <dl compact="compact">

  93. <dt>&lsquo;<samp><var>value</var>.is_constant ()</samp>&rsquo;</dt>

  94. <dd><p>Return true if <code>poly_int</code> <var>value</var> is a compile-time constant.

  95. </p>

  96. </dd>

  97. <dt>&lsquo;<samp><var>value</var>.is_constant (&amp;<var>c1</var>)</samp>&rsquo;</dt>

  98. <dd><p>Return true if <code>poly_int</code> <var>value</var> is a compile-time constant,

  99. storing it in <var>c1</var> if so.  <var>c1</var> must be able to hold all

  100. constant values of <var>value</var> without loss of precision.

  101. </p>

  102. </dd>

  103. <dt>&lsquo;<samp><var>value</var>.to_constant ()</samp>&rsquo;</dt>

  104. <dd><p>Assert that <var>value</var> is a compile-time constant and return its value.

  105. When using this function, please add a comment explaining why the

  106. condition is known to hold (for example, because an earlier phase

  107. of analysis rejected non-constants).

  108. </p>

  109. </dd>

  110. <dt>&lsquo;<samp><var>value</var>.to_shwi (&amp;<var>p2</var>)</samp>&rsquo;</dt>

  111. <dd><p>Return true if &lsquo;<samp>poly_int&lt;<var>N</var>, <var>T</var>&gt;</samp>&rsquo; <var>value</var> can be

  112. represented without loss of precision as a

  113. &lsquo;<samp>poly_int&lt;<var>N</var>, <code>HOST_WIDE_INT</code>&gt;</samp>&rsquo;, storing it in that

  114. form in <var>p2</var> if so.

  115. </p>

  116. </dd>

  117. <dt>&lsquo;<samp><var>value</var>.to_uhwi (&amp;<var>p2</var>)</samp>&rsquo;</dt>

  118. <dd><p>Return true if &lsquo;<samp>poly_int&lt;<var>N</var>, <var>T</var>&gt;</samp>&rsquo; <var>value</var> can be

  119. represented without loss of precision as a

  120. &lsquo;<samp>poly_int&lt;<var>N</var>, <code>unsigned HOST_WIDE_INT</code>&gt;</samp>&rsquo;, storing it in that

  121. form in <var>p2</var> if so.

  122. </p>

  123. </dd>

  124. <dt>&lsquo;<samp><var>value</var>.force_shwi ()</samp>&rsquo;</dt>

  125. <dd><p>Forcibly convert each coefficient of &lsquo;<samp>poly_int&lt;<var>N</var>, <var>T</var>&gt;</samp>&rsquo;

  126. <var>value</var> to <code>HOST_WIDE_INT</code>, truncating any that are out of range.

  127. Return the result as a &lsquo;<samp>poly_int&lt;<var>N</var>, <code>HOST_WIDE_INT</code>&gt;</samp>&rsquo;.

  128. </p>

  129. </dd>

  130. <dt>&lsquo;<samp><var>value</var>.force_uhwi ()</samp>&rsquo;</dt>

  131. <dd><p>Forcibly convert each coefficient of &lsquo;<samp>poly_int&lt;<var>N</var>, <var>T</var>&gt;</samp>&rsquo;

  132. <var>value</var> to <code>unsigned HOST_WIDE_INT</code>, truncating any that are

  133. out of range.  Return the result as a

  134. &lsquo;<samp>poly_int&lt;<var>N</var>, <code>unsigned HOST_WIDE_INT</code>&gt;</samp>&rsquo;.

  135. </p>

  136. </dd>

  137. <dt>&lsquo;<samp>wi::shwi (<var>value</var>, <var>precision</var>)</samp>&rsquo;</dt>

  138. <dd><p>Return a <code>poly_int</code> with the same value as <var>value</var>, but with

  139. the coefficients converted from <code>HOST_WIDE_INT</code> to <code>wide_int</code>.

  140. <var>precision</var> specifies the precision of the <code>wide_int</code> cofficients;

  141. if this is wider than a <code>HOST_WIDE_INT</code>, the coefficients of

  142. <var>value</var> will be sign-extended to fit.

  143. </p>

  144. </dd>

  145. <dt>&lsquo;<samp>wi::uhwi (<var>value</var>, <var>precision</var>)</samp>&rsquo;</dt>

  146. <dd><p>Like <code>wi::shwi</code>, except that <var>value</var> has coefficients of

  147. type <code>unsigned HOST_WIDE_INT</code>.  If <var>precision</var> is wider than

  148. a <code>HOST_WIDE_INT</code>, the coefficients of <var>value</var> will be

  149. zero-extended to fit.

  150. </p>

  151. </dd>

  152. <dt>&lsquo;<samp>wi::sext (<var>value</var>, <var>precision</var>)</samp>&rsquo;</dt>

  153. <dd><p>Return a <code>poly_int</code> of the same type as <var>value</var>, sign-extending

  154. every coefficient from the low <var>precision</var> bits.  This in effect

  155. applies <code>wi::sext</code> to each coefficient individually.

  156. </p>

  157. </dd>

  158. <dt>&lsquo;<samp>wi::zext (<var>value</var>, <var>precision</var>)</samp>&rsquo;</dt>

  159. <dd><p>Like <code>wi::sext</code>, but for zero extension.

  160. </p>

  161. </dd>

  162. <dt>&lsquo;<samp>poly_wide_int::from (<var>value</var>, <var>precision</var>, <var>sign</var>)</samp>&rsquo;</dt>

  163. <dd><p>Convert <var>value</var> to a <code>poly_wide_int</code> in which each coefficient

  164. has <var>precision</var> bits.  Extend the coefficients according to

  165. <var>sign</var> if the coefficients have fewer bits.

  166. </p>

  167. </dd>

  168. <dt>&lsquo;<samp>poly_offset_int::from (<var>value</var>, <var>sign</var>)</samp>&rsquo;</dt>

  169. <dd><p>Convert <var>value</var> to a <code>poly_offset_int</code>, extending its coefficients

  170. according to <var>sign</var> if they have fewer bits than <code>offset_int</code>.

  171. </p>

  172. </dd>

  173. <dt>&lsquo;<samp>poly_widest_int::from (<var>value</var>, <var>sign</var>)</samp>&rsquo;</dt>

  174. <dd><p>Convert <var>value</var> to a <code>poly_widest_int</code>, extending its coefficients

  175. according to <var>sign</var> if they have fewer bits than <code>widest_int</code>.

  176. </p></dd>

  177. </dl>

  178. 

  179. <hr>

  180. <div class="header">

  181. <p>

  182. Next: <a href="Miscellaneous-poly_005fint-routines.html#Miscellaneous-poly_005fint-routines" accesskey="n" rel="next">Miscellaneous <code>poly_int</code> routines</a>, Previous: <a href="Computing-bounds-on-poly_005fints.html#Computing-bounds-on-poly_005fints" accesskey="p" rel="prev">Computing bounds on <code>poly_int</code>s</a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> &nbsp; [<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>

  183. </div>

  184. 

  185. 

  186. 

  187. </body>

  188. </html>