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First step in fixing PR8927:

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Add a unnamed_addr bit to global variables and functions. This will be used
to indicate that the address is not significant and therefore the constant
or function can be merged with others.

If an optimization pass can show that an address is not used, it can set this.

Examples of things that can have this set by the FE are globals created to
hold string literals and C++ constructors.

Adding unnamed_addr to a non-const global should have no effect unless
an optimization can transform that global into a constant.

Aliases are not allowed to have unnamed_addr since I couldn't figure
out any use for it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123063 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2011-01-08 16:42:36 +00:00
parent 8368ac3688
commit bea4626f93
12 changed files with 98 additions and 13 deletions
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@@ -846,6 +846,10 @@ define i32 @main() { <i>; i32()* </i>&nbsp;
region of memory, and all memory objects in LLVM are accessed through
pointers.</p>
<p>Global variables can be marked with <tt>unnamed_addr</tt> which indicates
that the address is not significant, only the content. Constants marked
like this can be merged if they have the same content.</p>
<p>A global variable may be declared to reside in a target-specific numbered
address space. For targets that support them, address spaces may affect how
optimizations are performed and/or what target instructions are used to
@@ -885,7 +889,8 @@ define i32 @main() { <i>; i32()* </i>&nbsp;
<p>LLVM function definitions consist of the "<tt>define</tt>" keyword, an
optional <a href="#linkage">linkage type</a>, an optional
<a href="#visibility">visibility style</a>, an optional
<a href="#callingconv">calling convention</a>, a return type, an optional
<a href="#callingconv">calling convention</a>,
an optional <tt>unnamed_addr</tt> attribute, a return type, an optional
<a href="#paramattrs">parameter attribute</a> for the return type, a function
name, a (possibly empty) argument list (each with optional
<a href="#paramattrs">parameter attributes</a>), optional
@@ -896,7 +901,8 @@ define i32 @main() { <i>; i32()* </i>&nbsp;
<p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an
optional <a href="#linkage">linkage type</a>, an optional
<a href="#visibility">visibility style</a>, an optional
<a href="#callingconv">calling convention</a>, a return type, an optional
<a href="#callingconv">calling convention</a>,
an optional <tt>unnamed_addr</tt> attribute, a return type, an optional
<a href="#paramattrs">parameter attribute</a> for the return type, a function
name, a possibly empty list of arguments, an optional alignment, and an
optional <a href="#gc">garbage collector name</a>.</p>
@@ -922,6 +928,9 @@ define i32 @main() { <i>; i32()* </i>&nbsp;
specified, the function is forced to have at least that much alignment. All
alignments must be a power of 2.</p>
<p>If the <tt>unnamed_addr</tt> attribute is given, the address is know to not
be significant and two identical functions can be merged</p>.
<h5>Syntax:</h5>
<pre class="doc_code">
define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>]