Flags.html 28 KB

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  19. <title>GNU Compiler Collection (GCC) Internals: Flags</title>
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  62. <a name="Flags"></a>
  63. <div class="header">
  64. <p>
  65. Next: <a href="Machine-Modes.html#Machine-Modes" accesskey="n" rel="next">Machine Modes</a>, Previous: <a href="Special-Accessors.html#Special-Accessors" accesskey="p" rel="prev">Special Accessors</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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>
  66. </div>
  67. <hr>
  68. <a name="Flags-in-an-RTL-Expression"></a>
  69. <h3 class="section">13.5 Flags in an RTL Expression</h3>
  70. <a name="index-flags-in-RTL-expression"></a>
  71. <p>RTL expressions contain several flags (one-bit bit-fields)
  72. that are used in certain types of expression. Most often they
  73. are accessed with the following macros, which expand into lvalues.
  74. </p>
  75. <dl compact="compact">
  76. <dd><a name="index-CONSTANT_005fPOOL_005fADDRESS_005fP"></a>
  77. <a name="index-symbol_005fref-and-_002fu"></a>
  78. <a name="index-unchanging_002c-in-symbol_005fref"></a>
  79. </dd>
  80. <dt><code>CONSTANT_POOL_ADDRESS_P (<var>x</var>)</code></dt>
  81. <dd><p>Nonzero in a <code>symbol_ref</code> if it refers to part of the current
  82. function&rsquo;s constant pool. For most targets these addresses are in a
  83. <code>.rodata</code> section entirely separate from the function, but for
  84. some targets the addresses are close to the beginning of the function.
  85. In either case GCC assumes these addresses can be addressed directly,
  86. perhaps with the help of base registers.
  87. Stored in the <code>unchanging</code> field and printed as &lsquo;<samp>/u</samp>&rsquo;.
  88. </p>
  89. <a name="index-RTL_005fCONST_005fCALL_005fP"></a>
  90. <a name="index-call_005finsn-and-_002fu"></a>
  91. <a name="index-unchanging_002c-in-call_005finsn"></a>
  92. </dd>
  93. <dt><code>RTL_CONST_CALL_P (<var>x</var>)</code></dt>
  94. <dd><p>In a <code>call_insn</code> indicates that the insn represents a call to a
  95. const function. Stored in the <code>unchanging</code> field and printed as
  96. &lsquo;<samp>/u</samp>&rsquo;.
  97. </p>
  98. <a name="index-RTL_005fPURE_005fCALL_005fP"></a>
  99. <a name="index-call_005finsn-and-_002fi"></a>
  100. <a name="index-return_005fval_002c-in-call_005finsn"></a>
  101. </dd>
  102. <dt><code>RTL_PURE_CALL_P (<var>x</var>)</code></dt>
  103. <dd><p>In a <code>call_insn</code> indicates that the insn represents a call to a
  104. pure function. Stored in the <code>return_val</code> field and printed as
  105. &lsquo;<samp>/i</samp>&rsquo;.
  106. </p>
  107. <a name="index-RTL_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a>
  108. <a name="index-call_005finsn-and-_002fu-or-_002fi"></a>
  109. </dd>
  110. <dt><code>RTL_CONST_OR_PURE_CALL_P (<var>x</var>)</code></dt>
  111. <dd><p>In a <code>call_insn</code>, true if <code>RTL_CONST_CALL_P</code> or
  112. <code>RTL_PURE_CALL_P</code> is true.
  113. </p>
  114. <a name="index-RTL_005fLOOPING_005fCONST_005fOR_005fPURE_005fCALL_005fP"></a>
  115. <a name="index-call_005finsn-and-_002fc"></a>
  116. <a name="index-call_002c-in-call_005finsn"></a>
  117. </dd>
  118. <dt><code>RTL_LOOPING_CONST_OR_PURE_CALL_P (<var>x</var>)</code></dt>
  119. <dd><p>In a <code>call_insn</code> indicates that the insn represents a possibly
  120. infinite looping call to a const or pure function. Stored in the
  121. <code>call</code> field and printed as &lsquo;<samp>/c</samp>&rsquo;. Only true if one of
  122. <code>RTL_CONST_CALL_P</code> or <code>RTL_PURE_CALL_P</code> is true.
  123. </p>
  124. <a name="index-INSN_005fANNULLED_005fBRANCH_005fP"></a>
  125. <a name="index-jump_005finsn-and-_002fu"></a>
  126. <a name="index-call_005finsn-and-_002fu-1"></a>
  127. <a name="index-insn-and-_002fu"></a>
  128. <a name="index-unchanging_002c-in-jump_005finsn_002c-call_005finsn-and-insn"></a>
  129. </dd>
  130. <dt><code>INSN_ANNULLED_BRANCH_P (<var>x</var>)</code></dt>
  131. <dd><p>In a <code>jump_insn</code>, <code>call_insn</code>, or <code>insn</code> indicates
  132. that the branch is an annulling one. See the discussion under
  133. <code>sequence</code> below. Stored in the <code>unchanging</code> field and
  134. printed as &lsquo;<samp>/u</samp>&rsquo;.
  135. </p>
  136. <a name="index-INSN_005fDELETED_005fP"></a>
  137. <a name="index-insn-and-_002fv"></a>
  138. <a name="index-call_005finsn-and-_002fv"></a>
  139. <a name="index-jump_005finsn-and-_002fv"></a>
  140. <a name="index-code_005flabel-and-_002fv"></a>
  141. <a name="index-jump_005ftable_005fdata-and-_002fv"></a>
  142. <a name="index-barrier-and-_002fv"></a>
  143. <a name="index-note-and-_002fv"></a>
  144. <a name="index-volatil_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-code_005flabel_002c-jump_005ftable_005fdata_002c-barrier_002c-and-note"></a>
  145. </dd>
  146. <dt><code>INSN_DELETED_P (<var>x</var>)</code></dt>
  147. <dd><p>In an <code>insn</code>, <code>call_insn</code>, <code>jump_insn</code>, <code>code_label</code>,
  148. <code>jump_table_data</code>, <code>barrier</code>, or <code>note</code>,
  149. nonzero if the insn has been deleted. Stored in the
  150. <code>volatil</code> field and printed as &lsquo;<samp>/v</samp>&rsquo;.
  151. </p>
  152. <a name="index-INSN_005fFROM_005fTARGET_005fP"></a>
  153. <a name="index-insn-and-_002fs"></a>
  154. <a name="index-jump_005finsn-and-_002fs"></a>
  155. <a name="index-call_005finsn-and-_002fs"></a>
  156. <a name="index-in_005fstruct_002c-in-insn-and-jump_005finsn-and-call_005finsn"></a>
  157. </dd>
  158. <dt><code>INSN_FROM_TARGET_P (<var>x</var>)</code></dt>
  159. <dd><p>In an <code>insn</code> or <code>jump_insn</code> or <code>call_insn</code> in a delay
  160. slot of a branch, indicates that the insn
  161. is from the target of the branch. If the branch insn has
  162. <code>INSN_ANNULLED_BRANCH_P</code> set, this insn will only be executed if
  163. the branch is taken. For annulled branches with
  164. <code>INSN_FROM_TARGET_P</code> clear, the insn will be executed only if the
  165. branch is not taken. When <code>INSN_ANNULLED_BRANCH_P</code> is not set,
  166. this insn will always be executed. Stored in the <code>in_struct</code>
  167. field and printed as &lsquo;<samp>/s</samp>&rsquo;.
  168. </p>
  169. <a name="index-LABEL_005fPRESERVE_005fP"></a>
  170. <a name="index-code_005flabel-and-_002fi"></a>
  171. <a name="index-note-and-_002fi"></a>
  172. <a name="index-in_005fstruct_002c-in-code_005flabel-and-note"></a>
  173. </dd>
  174. <dt><code>LABEL_PRESERVE_P (<var>x</var>)</code></dt>
  175. <dd><p>In a <code>code_label</code> or <code>note</code>, indicates that the label is referenced by
  176. code or data not visible to the RTL of a given function.
  177. Labels referenced by a non-local goto will have this bit set. Stored
  178. in the <code>in_struct</code> field and printed as &lsquo;<samp>/s</samp>&rsquo;.
  179. </p>
  180. <a name="index-LABEL_005fREF_005fNONLOCAL_005fP"></a>
  181. <a name="index-label_005fref-and-_002fv"></a>
  182. <a name="index-reg_005flabel-and-_002fv"></a>
  183. <a name="index-volatil_002c-in-label_005fref-and-reg_005flabel"></a>
  184. </dd>
  185. <dt><code>LABEL_REF_NONLOCAL_P (<var>x</var>)</code></dt>
  186. <dd><p>In <code>label_ref</code> and <code>reg_label</code> expressions, nonzero if this is
  187. a reference to a non-local label.
  188. Stored in the <code>volatil</code> field and printed as &lsquo;<samp>/v</samp>&rsquo;.
  189. </p>
  190. <a name="index-MEM_005fKEEP_005fALIAS_005fSET_005fP"></a>
  191. <a name="index-mem-and-_002fj"></a>
  192. <a name="index-jump_002c-in-mem"></a>
  193. </dd>
  194. <dt><code>MEM_KEEP_ALIAS_SET_P (<var>x</var>)</code></dt>
  195. <dd><p>In <code>mem</code> expressions, 1 if we should keep the alias set for this
  196. mem unchanged when we access a component. Set to 1, for example, when we
  197. are already in a non-addressable component of an aggregate.
  198. Stored in the <code>jump</code> field and printed as &lsquo;<samp>/j</samp>&rsquo;.
  199. </p>
  200. <a name="index-MEM_005fVOLATILE_005fP"></a>
  201. <a name="index-mem-and-_002fv"></a>
  202. <a name="index-asm_005finput-and-_002fv"></a>
  203. <a name="index-asm_005foperands-and-_002fv"></a>
  204. <a name="index-volatil_002c-in-mem_002c-asm_005foperands_002c-and-asm_005finput"></a>
  205. </dd>
  206. <dt><code>MEM_VOLATILE_P (<var>x</var>)</code></dt>
  207. <dd><p>In <code>mem</code>, <code>asm_operands</code>, and <code>asm_input</code> expressions,
  208. nonzero for volatile memory references.
  209. Stored in the <code>volatil</code> field and printed as &lsquo;<samp>/v</samp>&rsquo;.
  210. </p>
  211. <a name="index-MEM_005fNOTRAP_005fP"></a>
  212. <a name="index-mem-and-_002fc"></a>
  213. <a name="index-call_002c-in-mem"></a>
  214. </dd>
  215. <dt><code>MEM_NOTRAP_P (<var>x</var>)</code></dt>
  216. <dd><p>In <code>mem</code>, nonzero for memory references that will not trap.
  217. Stored in the <code>call</code> field and printed as &lsquo;<samp>/c</samp>&rsquo;.
  218. </p>
  219. <a name="index-MEM_005fPOINTER"></a>
  220. <a name="index-mem-and-_002ff"></a>
  221. <a name="index-frame_005frelated_002c-in-mem"></a>
  222. </dd>
  223. <dt><code>MEM_POINTER (<var>x</var>)</code></dt>
  224. <dd><p>Nonzero in a <code>mem</code> if the memory reference holds a pointer.
  225. Stored in the <code>frame_related</code> field and printed as &lsquo;<samp>/f</samp>&rsquo;.
  226. </p>
  227. <a name="index-REG_005fFUNCTION_005fVALUE_005fP"></a>
  228. <a name="index-reg-and-_002fi"></a>
  229. <a name="index-return_005fval_002c-in-reg"></a>
  230. </dd>
  231. <dt><code>REG_FUNCTION_VALUE_P (<var>x</var>)</code></dt>
  232. <dd><p>Nonzero in a <code>reg</code> if it is the place in which this function&rsquo;s
  233. value is going to be returned. (This happens only in a hard
  234. register.) Stored in the <code>return_val</code> field and printed as
  235. &lsquo;<samp>/i</samp>&rsquo;.
  236. </p>
  237. <a name="index-REG_005fPOINTER"></a>
  238. <a name="index-reg-and-_002ff"></a>
  239. <a name="index-frame_005frelated_002c-in-reg"></a>
  240. </dd>
  241. <dt><code>REG_POINTER (<var>x</var>)</code></dt>
  242. <dd><p>Nonzero in a <code>reg</code> if the register holds a pointer. Stored in the
  243. <code>frame_related</code> field and printed as &lsquo;<samp>/f</samp>&rsquo;.
  244. </p>
  245. <a name="index-REG_005fUSERVAR_005fP"></a>
  246. <a name="index-reg-and-_002fv"></a>
  247. <a name="index-volatil_002c-in-reg"></a>
  248. </dd>
  249. <dt><code>REG_USERVAR_P (<var>x</var>)</code></dt>
  250. <dd><p>In a <code>reg</code>, nonzero if it corresponds to a variable present in
  251. the user&rsquo;s source code. Zero for temporaries generated internally by
  252. the compiler. Stored in the <code>volatil</code> field and printed as
  253. &lsquo;<samp>/v</samp>&rsquo;.
  254. </p>
  255. <p>The same hard register may be used also for collecting the values of
  256. functions called by this one, but <code>REG_FUNCTION_VALUE_P</code> is zero
  257. in this kind of use.
  258. </p>
  259. <a name="index-RTX_005fFRAME_005fRELATED_005fP"></a>
  260. <a name="index-insn-and-_002ff"></a>
  261. <a name="index-call_005finsn-and-_002ff"></a>
  262. <a name="index-jump_005finsn-and-_002ff"></a>
  263. <a name="index-barrier-and-_002ff"></a>
  264. <a name="index-set-and-_002ff"></a>
  265. <a name="index-frame_005frelated_002c-in-insn_002c-call_005finsn_002c-jump_005finsn_002c-barrier_002c-and-set"></a>
  266. </dd>
  267. <dt><code>RTX_FRAME_RELATED_P (<var>x</var>)</code></dt>
  268. <dd><p>Nonzero in an <code>insn</code>, <code>call_insn</code>, <code>jump_insn</code>,
  269. <code>barrier</code>, or <code>set</code> which is part of a function prologue
  270. and sets the stack pointer, sets the frame pointer, or saves a register.
  271. This flag should also be set on an instruction that sets up a temporary
  272. register to use in place of the frame pointer.
  273. Stored in the <code>frame_related</code> field and printed as &lsquo;<samp>/f</samp>&rsquo;.
  274. </p>
  275. <p>In particular, on RISC targets where there are limits on the sizes of
  276. immediate constants, it is sometimes impossible to reach the register
  277. save area directly from the stack pointer. In that case, a temporary
  278. register is used that is near enough to the register save area, and the
  279. Canonical Frame Address, i.e., DWARF2&rsquo;s logical frame pointer, register
  280. must (temporarily) be changed to be this temporary register. So, the
  281. instruction that sets this temporary register must be marked as
  282. <code>RTX_FRAME_RELATED_P</code>.
  283. </p>
  284. <p>If the marked instruction is overly complex (defined in terms of what
  285. <code>dwarf2out_frame_debug_expr</code> can handle), you will also have to
  286. create a <code>REG_FRAME_RELATED_EXPR</code> note and attach it to the
  287. instruction. This note should contain a simple expression of the
  288. computation performed by this instruction, i.e., one that
  289. <code>dwarf2out_frame_debug_expr</code> can handle.
  290. </p>
  291. <p>This flag is required for exception handling support on targets with RTL
  292. prologues.
  293. </p>
  294. <a name="index-MEM_005fREADONLY_005fP"></a>
  295. <a name="index-mem-and-_002fu"></a>
  296. <a name="index-unchanging_002c-in-mem"></a>
  297. </dd>
  298. <dt><code>MEM_READONLY_P (<var>x</var>)</code></dt>
  299. <dd><p>Nonzero in a <code>mem</code>, if the memory is statically allocated and read-only.
  300. </p>
  301. <p>Read-only in this context means never modified during the lifetime of the
  302. program, not necessarily in ROM or in write-disabled pages. A common
  303. example of the later is a shared library&rsquo;s global offset table. This
  304. table is initialized by the runtime loader, so the memory is technically
  305. writable, but after control is transferred from the runtime loader to the
  306. application, this memory will never be subsequently modified.
  307. </p>
  308. <p>Stored in the <code>unchanging</code> field and printed as &lsquo;<samp>/u</samp>&rsquo;.
  309. </p>
  310. <a name="index-SCHED_005fGROUP_005fP"></a>
  311. <a name="index-insn-and-_002fs-1"></a>
  312. <a name="index-call_005finsn-and-_002fs-1"></a>
  313. <a name="index-jump_005finsn-and-_002fs-1"></a>
  314. <a name="index-jump_005ftable_005fdata-and-_002fs"></a>
  315. <a name="index-in_005fstruct_002c-in-insn_002c-call_005finsn_002c-jump_005finsn-and-jump_005ftable_005fdata"></a>
  316. </dd>
  317. <dt><code>SCHED_GROUP_P (<var>x</var>)</code></dt>
  318. <dd><p>During instruction scheduling, in an <code>insn</code>, <code>call_insn</code>,
  319. <code>jump_insn</code> or <code>jump_table_data</code>, indicates that the
  320. previous insn must be scheduled together with this insn. This is used to
  321. ensure that certain groups of instructions will not be split up by the
  322. instruction scheduling pass, for example, <code>use</code> insns before
  323. a <code>call_insn</code> may not be separated from the <code>call_insn</code>.
  324. Stored in the <code>in_struct</code> field and printed as &lsquo;<samp>/s</samp>&rsquo;.
  325. </p>
  326. <a name="index-SET_005fIS_005fRETURN_005fP"></a>
  327. <a name="index-insn-and-_002fj"></a>
  328. <a name="index-jump_002c-in-insn"></a>
  329. </dd>
  330. <dt><code>SET_IS_RETURN_P (<var>x</var>)</code></dt>
  331. <dd><p>For a <code>set</code>, nonzero if it is for a return.
  332. Stored in the <code>jump</code> field and printed as &lsquo;<samp>/j</samp>&rsquo;.
  333. </p>
  334. <a name="index-SIBLING_005fCALL_005fP"></a>
  335. <a name="index-call_005finsn-and-_002fj"></a>
  336. <a name="index-jump_002c-in-call_005finsn"></a>
  337. </dd>
  338. <dt><code>SIBLING_CALL_P (<var>x</var>)</code></dt>
  339. <dd><p>For a <code>call_insn</code>, nonzero if the insn is a sibling call.
  340. Stored in the <code>jump</code> field and printed as &lsquo;<samp>/j</samp>&rsquo;.
  341. </p>
  342. <a name="index-STRING_005fPOOL_005fADDRESS_005fP"></a>
  343. <a name="index-symbol_005fref-and-_002ff"></a>
  344. <a name="index-frame_005frelated_002c-in-symbol_005fref"></a>
  345. </dd>
  346. <dt><code>STRING_POOL_ADDRESS_P (<var>x</var>)</code></dt>
  347. <dd><p>For a <code>symbol_ref</code> expression, nonzero if it addresses this function&rsquo;s
  348. string constant pool.
  349. Stored in the <code>frame_related</code> field and printed as &lsquo;<samp>/f</samp>&rsquo;.
  350. </p>
  351. <a name="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fP"></a>
  352. <a name="index-subreg-and-_002fu-and-_002fv"></a>
  353. <a name="index-unchanging_002c-in-subreg"></a>
  354. <a name="index-volatil_002c-in-subreg"></a>
  355. </dd>
  356. <dt><code>SUBREG_PROMOTED_UNSIGNED_P (<var>x</var>)</code></dt>
  357. <dd><p>Returns a value greater then zero for a <code>subreg</code> that has
  358. <code>SUBREG_PROMOTED_VAR_P</code> nonzero if the object being referenced is kept
  359. zero-extended, zero if it is kept sign-extended, and less then zero if it is
  360. extended some other way via the <code>ptr_extend</code> instruction.
  361. Stored in the <code>unchanging</code>
  362. field and <code>volatil</code> field, printed as &lsquo;<samp>/u</samp>&rsquo; and &lsquo;<samp>/v</samp>&rsquo;.
  363. This macro may only be used to get the value it may not be used to change
  364. the value. Use <code>SUBREG_PROMOTED_UNSIGNED_SET</code> to change the value.
  365. </p>
  366. <a name="index-SUBREG_005fPROMOTED_005fUNSIGNED_005fSET"></a>
  367. <a name="index-subreg-and-_002fu"></a>
  368. <a name="index-unchanging_002c-in-subreg-1"></a>
  369. <a name="index-volatil_002c-in-subreg-1"></a>
  370. </dd>
  371. <dt><code>SUBREG_PROMOTED_UNSIGNED_SET (<var>x</var>)</code></dt>
  372. <dd><p>Set the <code>unchanging</code> and <code>volatil</code> fields in a <code>subreg</code>
  373. to reflect zero, sign, or other extension. If <code>volatil</code> is
  374. zero, then <code>unchanging</code> as nonzero means zero extension and as
  375. zero means sign extension. If <code>volatil</code> is nonzero then some
  376. other type of extension was done via the <code>ptr_extend</code> instruction.
  377. </p>
  378. <a name="index-SUBREG_005fPROMOTED_005fVAR_005fP"></a>
  379. <a name="index-subreg-and-_002fs"></a>
  380. <a name="index-in_005fstruct_002c-in-subreg"></a>
  381. </dd>
  382. <dt><code>SUBREG_PROMOTED_VAR_P (<var>x</var>)</code></dt>
  383. <dd><p>Nonzero in a <code>subreg</code> if it was made when accessing an object that
  384. was promoted to a wider mode in accord with the <code>PROMOTED_MODE</code> machine
  385. description macro (see <a href="Storage-Layout.html#Storage-Layout">Storage Layout</a>). In this case, the mode of
  386. the <code>subreg</code> is the declared mode of the object and the mode of
  387. <code>SUBREG_REG</code> is the mode of the register that holds the object.
  388. Promoted variables are always either sign- or zero-extended to the wider
  389. mode on every assignment. Stored in the <code>in_struct</code> field and
  390. printed as &lsquo;<samp>/s</samp>&rsquo;.
  391. </p>
  392. <a name="index-SYMBOL_005fREF_005fUSED"></a>
  393. <a name="index-used_002c-in-symbol_005fref"></a>
  394. </dd>
  395. <dt><code>SYMBOL_REF_USED (<var>x</var>)</code></dt>
  396. <dd><p>In a <code>symbol_ref</code>, indicates that <var>x</var> has been used. This is
  397. normally only used to ensure that <var>x</var> is only declared external
  398. once. Stored in the <code>used</code> field.
  399. </p>
  400. <a name="index-SYMBOL_005fREF_005fWEAK"></a>
  401. <a name="index-symbol_005fref-and-_002fi"></a>
  402. <a name="index-return_005fval_002c-in-symbol_005fref"></a>
  403. </dd>
  404. <dt><code>SYMBOL_REF_WEAK (<var>x</var>)</code></dt>
  405. <dd><p>In a <code>symbol_ref</code>, indicates that <var>x</var> has been declared weak.
  406. Stored in the <code>return_val</code> field and printed as &lsquo;<samp>/i</samp>&rsquo;.
  407. </p>
  408. <a name="index-SYMBOL_005fREF_005fFLAG"></a>
  409. <a name="index-symbol_005fref-and-_002fv"></a>
  410. <a name="index-volatil_002c-in-symbol_005fref"></a>
  411. </dd>
  412. <dt><code>SYMBOL_REF_FLAG (<var>x</var>)</code></dt>
  413. <dd><p>In a <code>symbol_ref</code>, this is used as a flag for machine-specific purposes.
  414. Stored in the <code>volatil</code> field and printed as &lsquo;<samp>/v</samp>&rsquo;.
  415. </p>
  416. <p>Most uses of <code>SYMBOL_REF_FLAG</code> are historic and may be subsumed
  417. by <code>SYMBOL_REF_FLAGS</code>. Certainly use of <code>SYMBOL_REF_FLAGS</code>
  418. is mandatory if the target requires more than one bit of storage.
  419. </p>
  420. <a name="index-PREFETCH_005fSCHEDULE_005fBARRIER_005fP"></a>
  421. <a name="index-prefetch-and-_002fv"></a>
  422. <a name="index-volatile_002c-in-prefetch"></a>
  423. </dd>
  424. <dt><code>PREFETCH_SCHEDULE_BARRIER_P (<var>x</var>)</code></dt>
  425. <dd><p>In a <code>prefetch</code>, indicates that the prefetch is a scheduling barrier.
  426. No other INSNs will be moved over it.
  427. Stored in the <code>volatil</code> field and printed as &lsquo;<samp>/v</samp>&rsquo;.
  428. </p></dd>
  429. </dl>
  430. <p>These are the fields to which the above macros refer:
  431. </p>
  432. <dl compact="compact">
  433. <dd><a name="index-call"></a>
  434. <a name="index-_002fc-in-RTL-dump"></a>
  435. </dd>
  436. <dt><code>call</code></dt>
  437. <dd><p>In a <code>mem</code>, 1 means that the memory reference will not trap.
  438. </p>
  439. <p>In a <code>call</code>, 1 means that this pure or const call may possibly
  440. infinite loop.
  441. </p>
  442. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/c</samp>&rsquo;.
  443. </p>
  444. <a name="index-frame_005frelated"></a>
  445. <a name="index-_002ff-in-RTL-dump"></a>
  446. </dd>
  447. <dt><code>frame_related</code></dt>
  448. <dd><p>In an <code>insn</code> or <code>set</code> expression, 1 means that it is part of
  449. a function prologue and sets the stack pointer, sets the frame pointer,
  450. saves a register, or sets up a temporary register to use in place of the
  451. frame pointer.
  452. </p>
  453. <p>In <code>reg</code> expressions, 1 means that the register holds a pointer.
  454. </p>
  455. <p>In <code>mem</code> expressions, 1 means that the memory reference holds a pointer.
  456. </p>
  457. <p>In <code>symbol_ref</code> expressions, 1 means that the reference addresses
  458. this function&rsquo;s string constant pool.
  459. </p>
  460. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/f</samp>&rsquo;.
  461. </p>
  462. <a name="index-in_005fstruct"></a>
  463. <a name="index-_002fs-in-RTL-dump"></a>
  464. </dd>
  465. <dt><code>in_struct</code></dt>
  466. <dd><p>In <code>reg</code> expressions, it is 1 if the register has its entire life
  467. contained within the test expression of some loop.
  468. </p>
  469. <p>In <code>subreg</code> expressions, 1 means that the <code>subreg</code> is accessing
  470. an object that has had its mode promoted from a wider mode.
  471. </p>
  472. <p>In <code>label_ref</code> expressions, 1 means that the referenced label is
  473. outside the innermost loop containing the insn in which the <code>label_ref</code>
  474. was found.
  475. </p>
  476. <p>In <code>code_label</code> expressions, it is 1 if the label may never be deleted.
  477. This is used for labels which are the target of non-local gotos. Such a
  478. label that would have been deleted is replaced with a <code>note</code> of type
  479. <code>NOTE_INSN_DELETED_LABEL</code>.
  480. </p>
  481. <p>In an <code>insn</code> during dead-code elimination, 1 means that the insn is
  482. dead code.
  483. </p>
  484. <p>In an <code>insn</code> or <code>jump_insn</code> during reorg for an insn in the
  485. delay slot of a branch,
  486. 1 means that this insn is from the target of the branch.
  487. </p>
  488. <p>In an <code>insn</code> during instruction scheduling, 1 means that this insn
  489. must be scheduled as part of a group together with the previous insn.
  490. </p>
  491. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/s</samp>&rsquo;.
  492. </p>
  493. <a name="index-return_005fval"></a>
  494. <a name="index-_002fi-in-RTL-dump"></a>
  495. </dd>
  496. <dt><code>return_val</code></dt>
  497. <dd><p>In <code>reg</code> expressions, 1 means the register contains
  498. the value to be returned by the current function. On
  499. machines that pass parameters in registers, the same register number
  500. may be used for parameters as well, but this flag is not set on such
  501. uses.
  502. </p>
  503. <p>In <code>symbol_ref</code> expressions, 1 means the referenced symbol is weak.
  504. </p>
  505. <p>In <code>call</code> expressions, 1 means the call is pure.
  506. </p>
  507. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/i</samp>&rsquo;.
  508. </p>
  509. <a name="index-jump"></a>
  510. <a name="index-_002fj-in-RTL-dump"></a>
  511. </dd>
  512. <dt><code>jump</code></dt>
  513. <dd><p>In a <code>mem</code> expression, 1 means we should keep the alias set for this
  514. mem unchanged when we access a component.
  515. </p>
  516. <p>In a <code>set</code>, 1 means it is for a return.
  517. </p>
  518. <p>In a <code>call_insn</code>, 1 means it is a sibling call.
  519. </p>
  520. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/j</samp>&rsquo;.
  521. </p>
  522. <a name="index-unchanging"></a>
  523. <a name="index-_002fu-in-RTL-dump"></a>
  524. </dd>
  525. <dt><code>unchanging</code></dt>
  526. <dd><p>In <code>reg</code> and <code>mem</code> expressions, 1 means
  527. that the value of the expression never changes.
  528. </p>
  529. <p>In <code>subreg</code> expressions, it is 1 if the <code>subreg</code> references an
  530. unsigned object whose mode has been promoted to a wider mode.
  531. </p>
  532. <p>In an <code>insn</code> or <code>jump_insn</code> in the delay slot of a branch
  533. instruction, 1 means an annulling branch should be used.
  534. </p>
  535. <p>In a <code>symbol_ref</code> expression, 1 means that this symbol addresses
  536. something in the per-function constant pool.
  537. </p>
  538. <p>In a <code>call_insn</code> 1 means that this instruction is a call to a const
  539. function.
  540. </p>
  541. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/u</samp>&rsquo;.
  542. </p>
  543. <a name="index-used"></a>
  544. </dd>
  545. <dt><code>used</code></dt>
  546. <dd><p>This flag is used directly (without an access macro) at the end of RTL
  547. generation for a function, to count the number of times an expression
  548. appears in insns. Expressions that appear more than once are copied,
  549. according to the rules for shared structure (see <a href="Sharing.html#Sharing">Sharing</a>).
  550. </p>
  551. <p>For a <code>reg</code>, it is used directly (without an access macro) by the
  552. leaf register renumbering code to ensure that each register is only
  553. renumbered once.
  554. </p>
  555. <p>In a <code>symbol_ref</code>, it indicates that an external declaration for
  556. the symbol has already been written.
  557. </p>
  558. <a name="index-volatil"></a>
  559. <a name="index-_002fv-in-RTL-dump"></a>
  560. </dd>
  561. <dt><code>volatil</code></dt>
  562. <dd><a name="index-volatile-memory-references"></a>
  563. <p>In a <code>mem</code>, <code>asm_operands</code>, or <code>asm_input</code>
  564. expression, it is 1 if the memory
  565. reference is volatile. Volatile memory references may not be deleted,
  566. reordered or combined.
  567. </p>
  568. <p>In a <code>symbol_ref</code> expression, it is used for machine-specific
  569. purposes.
  570. </p>
  571. <p>In a <code>reg</code> expression, it is 1 if the value is a user-level variable.
  572. 0 indicates an internal compiler temporary.
  573. </p>
  574. <p>In an <code>insn</code>, 1 means the insn has been deleted.
  575. </p>
  576. <p>In <code>label_ref</code> and <code>reg_label</code> expressions, 1 means a reference
  577. to a non-local label.
  578. </p>
  579. <p>In <code>prefetch</code> expressions, 1 means that the containing insn is a
  580. scheduling barrier.
  581. </p>
  582. <p>In an RTL dump, this flag is represented as &lsquo;<samp>/v</samp>&rsquo;.
  583. </p></dd>
  584. </dl>
  585. <hr>
  586. <div class="header">
  587. <p>
  588. Next: <a href="Machine-Modes.html#Machine-Modes" accesskey="n" rel="next">Machine Modes</a>, Previous: <a href="Special-Accessors.html#Special-Accessors" accesskey="p" rel="prev">Special Accessors</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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>
  589. </div>
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  591. </html>