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Clarify that ptrtoint+inttoptr are an alternative to GEP which are

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not restricted by the GEP rules.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96598 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-02-18 18:40:29 +00:00
parent a52eeb93e0
commit e921792509
1 changed files with 14 additions and 6 deletions
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docs/AdvancedGetElementPtr.html
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@ -200,9 +200,9 @@
to null?</b></a>
</div>
<div class="doc_text">
<p>You can compute an address that way, but you can't use that pointer to
actually access the object if you do, unless the object is managed
outside of LLVM.</p>
<p>You can compute an address that way, but if you use GEP to do the add,
you can't use that pointer to actually access the object, unless the
object is managed outside of LLVM.</p>
<p>The underlying integer computation is sufficiently defined; null has a
defined value -- zero -- and you can add whatever value you want to it.</p>
@ -211,6 +211,11 @@
object with such a pointer. This includes GlobalVariables, Allocas, and
objects pointed to by noalias pointers.</p>
<p>If you really need this functionality, you can do the arithmetic with
explicit integer instructions, and use inttoptr to convert the result to
an address. Most of GEP's special aliasing rules do not apply to pointers
computed from ptrtoint, arithmetic, and inttoptr sequences.</p>
</div>
<!-- *********************************************************************** -->
@ -219,9 +224,12 @@
that value to one address to compute the other address?</b></a>
</div>
<div class="doc_text">
<p>As with arithmetic on null, You can compute an address that way, but
you can't use that pointer to actually access the object if you do,
unless the object is managed outside of LLVM.</p>
<p>As with arithmetic on null, You can use GEP to compute an address that
way, but you can't use that pointer to actually access the object if you
do, unless the object is managed outside of LLVM.</p>
<p>Also as above, ptrtoint and inttoptr provide an alternative way to do this
which do not have this restriction.</p>
</div>