visus
/
toolchain-gcc-arm-embedded
Watch 1
Star 0
Fork 0
Code Issues 0 Pull Requests 0 Releases 0 Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
2 Commits
1 Branch
Branch: main
Branches Tags
${ item.name }
Create branch ${ searchTerm }
from 'main'
${ noResults }
toolchain-gcc-arm-embedded/share/doc/gcc-arm-none-eabi/html/gccint/Shrink_002dwrapping-separat...

154 lines
7.9KB
Raw Permalink Blame History 

  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- Copyright (C) 1988-2020 Free Software Foundation, Inc.

  4. 

  5. Permission is granted to copy, distribute and/or modify this document

  6. under the terms of the GNU Free Documentation License, Version 1.3 or

  7. any later version published by the Free Software Foundation; with the

  8. Invariant Sections being "Funding Free Software", the Front-Cover

  9. Texts being (a) (see below), and with the Back-Cover Texts being (b)

  10. (see below).  A copy of the license is included in the section entitled

  11. "GNU Free Documentation License".

  12. 

  13. (a) The FSF's Front-Cover Text is:

  14. 

  15. A GNU Manual

  16. 

  17. (b) The FSF's Back-Cover Text is:

  18. 

  19. You have freedom to copy and modify this GNU Manual, like GNU

  20.      software.  Copies published by the Free Software Foundation raise

  21.      funds for GNU development. -->

  22. <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ -->

  23. <head>

  24. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  25. <title>Shrink-wrapping separate components (GNU Compiler Collection (GCC) Internals)</title>

  26. 

  27. <meta name="description" content="Shrink-wrapping separate components (GNU Compiler Collection (GCC) Internals)">

  28. <meta name="keywords" content="Shrink-wrapping separate components (GNU Compiler Collection (GCC) Internals)">

  29. <meta name="resource-type" content="document">

  30. <meta name="distribution" content="global">

  31. <meta name="Generator" content="makeinfo">

  32. <link href="index.html#Top" rel="start" title="Top">

  33. <link href="Option-Index.html#Option-Index" rel="index" title="Option Index">

  34. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  35. <link href="Stack-and-Calling.html#Stack-and-Calling" rel="up" title="Stack and Calling">

  36. <link href="Stack-Smashing-Protection.html#Stack-Smashing-Protection" rel="next" title="Stack Smashing Protection">

  37. <link href="Tail-Calls.html#Tail-Calls" rel="prev" title="Tail Calls">

  38. <style type="text/css">

  39. <!--

  40. a.summary-letter {text-decoration: none}

  41. blockquote.indentedblock {margin-right: 0em}

  42. blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}

  43. blockquote.smallquotation {font-size: smaller}

  44. div.display {margin-left: 3.2em}

  45. div.example {margin-left: 3.2em}

  46. div.lisp {margin-left: 3.2em}

  47. div.smalldisplay {margin-left: 3.2em}

  48. div.smallexample {margin-left: 3.2em}

  49. div.smalllisp {margin-left: 3.2em}

  50. kbd {font-style: oblique}

  51. pre.display {font-family: inherit}

  52. pre.format {font-family: inherit}

  53. pre.menu-comment {font-family: serif}

  54. pre.menu-preformatted {font-family: serif}

  55. pre.smalldisplay {font-family: inherit; font-size: smaller}

  56. pre.smallexample {font-size: smaller}

  57. pre.smallformat {font-family: inherit; font-size: smaller}

  58. pre.smalllisp {font-size: smaller}

  59. span.nolinebreak {white-space: nowrap}

  60. span.roman {font-family: initial; font-weight: normal}

  61. span.sansserif {font-family: sans-serif; font-weight: normal}

  62. ul.no-bullet {list-style: none}

  63. -->

  64. </style>

  65. 

  66. 

  67. </head>

  68. 

  69. <body lang="en">

  70. <a name="Shrink_002dwrapping-separate-components"></a>

  71. <div class="header">

  72. <p>

  73. Next: <a href="Stack-Smashing-Protection.html#Stack-Smashing-Protection" accesskey="n" rel="next">Stack Smashing Protection</a>, Previous: <a href="Tail-Calls.html#Tail-Calls" accesskey="p" rel="prev">Tail Calls</a>, Up: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="u" rel="up">Stack and Calling</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="Shrink_002dwrapping-separate-components-1"></a>

  77. <h4 class="subsection">18.9.14 Shrink-wrapping separate components</h4>

  78. <a name="index-shrink_002dwrapping-separate-components"></a>

  79. 

  80. <p>The prologue may perform a variety of target dependent tasks such as

  81. saving callee-saved registers, saving the return address, aligning the

  82. stack, creating a stack frame, initializing the PIC register, setting

  83. up the static chain, etc.

  84. </p>

  85. <p>On some targets some of these tasks may be independent of others and

  86. thus may be shrink-wrapped separately.  These independent tasks are

  87. referred to as components and are handled generically by the target

  88. independent parts of GCC.

  89. </p>

  90. <p>Using the following hooks those prologue or epilogue components can be

  91. shrink-wrapped separately, so that the initialization (and possibly

  92. teardown) those components do is not done as frequently on execution

  93. paths where this would unnecessary.

  94. </p>

  95. <p>What exactly those components are is up to the target code; the generic

  96. code treats them abstractly, as a bit in an <code>sbitmap</code>.  These

  97. <code>sbitmap</code>s are allocated by the <code>shrink_wrap.get_separate_components</code>

  98. and <code>shrink_wrap.components_for_bb</code> hooks, and deallocated by the

  99. generic code.

  100. </p>

  101. <dl>

  102. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fGET_005fSEPARATE_005fCOMPONENTS"></a>Target Hook: <em>sbitmap</em> <strong>TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS</strong> <em>(void)</em></dt>

  103. <dd><p>This hook should return an <code>sbitmap</code> with the bits set for those

  104. components that can be separately shrink-wrapped in the current function.

  105. Return <code>NULL</code> if the current function should not get any separate

  106. shrink-wrapping.

  107. Don&rsquo;t define this hook if it would always return <code>NULL</code>.

  108. If it is defined, the other hooks in this group have to be defined as well.

  109. </p></dd></dl>

  110. 

  111. <dl>

  112. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fCOMPONENTS_005fFOR_005fBB"></a>Target Hook: <em>sbitmap</em> <strong>TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB</strong> <em>(basic_block)</em></dt>

  113. <dd><p>This hook should return an <code>sbitmap</code> with the bits set for those

  114. components where either the prologue component has to be executed before

  115. the <code>basic_block</code>, or the epilogue component after it, or both.

  116. </p></dd></dl>

  117. 

  118. <dl>

  119. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fDISQUALIFY_005fCOMPONENTS"></a>Target Hook: <em>void</em> <strong>TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS</strong> <em>(sbitmap <var>components</var>, edge <var>e</var>, sbitmap <var>edge_components</var>, bool <var>is_prologue</var>)</em></dt>

  120. <dd><p>This hook should clear the bits in the <var>components</var> bitmap for those

  121. components in <var>edge_components</var> that the target cannot handle on edge

  122. <var>e</var>, where <var>is_prologue</var> says if this is for a prologue or an

  123. epilogue instead.

  124. </p></dd></dl>

  125. 

  126. <dl>

  127. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fEMIT_005fPROLOGUE_005fCOMPONENTS"></a>Target Hook: <em>void</em> <strong>TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS</strong> <em>(sbitmap)</em></dt>

  128. <dd><p>Emit prologue insns for the components indicated by the parameter.

  129. </p></dd></dl>

  130. 

  131. <dl>

  132. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fEMIT_005fEPILOGUE_005fCOMPONENTS"></a>Target Hook: <em>void</em> <strong>TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS</strong> <em>(sbitmap)</em></dt>

  133. <dd><p>Emit epilogue insns for the components indicated by the parameter.

  134. </p></dd></dl>

  135. 

  136. <dl>

  137. <dt><a name="index-TARGET_005fSHRINK_005fWRAP_005fSET_005fHANDLED_005fCOMPONENTS"></a>Target Hook: <em>void</em> <strong>TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS</strong> <em>(sbitmap)</em></dt>

  138. <dd><p>Mark the components in the parameter as handled, so that the

  139. <code>prologue</code> and <code>epilogue</code> named patterns know to ignore those

  140. components.  The target code should not hang on to the <code>sbitmap</code>, it

  141. will be deleted after this call.

  142. </p></dd></dl>

  143. 

  144. <hr>

  145. <div class="header">

  146. <p>

  147. Next: <a href="Stack-Smashing-Protection.html#Stack-Smashing-Protection" accesskey="n" rel="next">Stack Smashing Protection</a>, Previous: <a href="Tail-Calls.html#Tail-Calls" accesskey="p" rel="prev">Tail Calls</a>, Up: <a href="Stack-and-Calling.html#Stack-and-Calling" accesskey="u" rel="up">Stack and Calling</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>

  148. </div>

  149. 

  150. 

  151. 

  152. </body>

  153. </html>