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Note the relationship between C99 restrict and LLVM noalias, and

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clarify a few other things.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107659 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-07-06 15:26:33 +00:00
parent 36335be3b9
commit ff70fe40aa
2 changed files with 15 additions and 4 deletions
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6
docs/GetElementPtr.html
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@ -64,7 +64,8 @@
<div class="doc_text">
<p>This document seeks to dispel the mystery and confusion surrounding LLVM's
GetElementPtr (GEP) instruction. Questions about the wily GEP instruction are
<a href="LangRef.html#i_getelementptr">GetElementPtr</a> (GEP) instruction.
Questions about the wily GEP instruction are
probably the most frequently occurring questions once a developer gets down to
coding with LLVM. Here we lay out the sources of confusion and show that the
GEP instruction is really quite simple.
@ -653,7 +654,8 @@ idx3 = (char*) &amp;MyVar + 8
<li>Support C, C-like languages, and languages which can be
conceptually lowered into C (this covers a lot).</li>
<li>Support optimizations such as those that are common in
C compilers.</li>
C compilers. In particular, GEP is a cornerstone of LLVM's
<a href="LangRef.html#pointeraliasing">pointer aliasing model</a>.</li>
<li>Provide a consistent method for computing addresses so that
address computations don't need to be a part of load and
store instructions in the IR.</li>

13
docs/LangRef.html
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@ -1062,7 +1062,15 @@ declare signext i8 @returns_signed_char()
The caller shares the responsibility with the callee for ensuring that
these requirements are met.
For further details, please see the discussion of the NoAlias response in
<a href="AliasAnalysis.html#MustMayNo">alias analysis</a>.</dd>
<a href="AliasAnalysis.html#MustMayNo">alias analysis</a>.<br>
<br>
Note that this definition of <tt>noalias<tt> is intentionally
similar to the definition of <tt>restrict<tt> in C99 for function
arguments, thought it is slightly weaker.
<br>
For function return values, C99's <tt>restrict</tt> is not meaningful,
while LLVM's <tt>noalias</tt> is.
</dd>
<dt><tt><b><a name="nocapture">nocapture</a></b></tt></dt>
<dd>This indicates that the callee does not make any copies of the pointer
@ -2397,7 +2405,8 @@ has undefined behavior.</p>
<li>An instruction with externally visible side effects depends on the most
recent preceding instruction with externally visible side effects, following
the order in the IR. (This includes volatile loads and stores.)</li>
the order in the IR. (This includes
<a href="#volatile">volatile operations</a>.)</li>
<li>An instruction <i>control-depends</i> on a
<a href="#terminators">terminator instruction</a>