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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - BBVectorizer moves stores across calls"
href="http://llvm.org/bugs/show_bug.cgi?id=20600">20600</a>
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<th>Summary</th>
<td>BBVectorizer moves stores across calls
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>sanjoy@playingwithpointers.com
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Running "opt -bb-vectorize" on the following IR
target datalayout = "e"
declare void @external(i32*)
define void @foo(i32* %x, i32* %y) {
entry:
%y1.addr = getelementptr i32* %y, i32 0
%y1 = load i32* %y1.addr
%y2.addr = getelementptr i32* %y, i32 1
%y2 = load i32* %y2.addr
%x1 = getelementptr i32* %x, i32 0
store i32 %y1, i32* %x1, align 4
call void @external(i32* %x)
%x2 = getelementptr i32* %x, i32 1
store i32 %y2, i32* %x2, align 4
ret void
}
results in
target datalayout = "e"
declare void @external(i32*)
define void @foo(i32* %x, i32* %y) {
entry:
%y1.v.i0 = bitcast i32* %y to <2 x i32>*
%y1 = load <2 x i32>* %y1.v.i0
%0 = bitcast i32* %x to <2 x i32>*
store <2 x i32> %y1, <2 x i32>* %0, align 4
call void @external(i32* %x)
ret void
}
This is problematic since the transform effectively moves a store to
'%x' from after the call to '@external' (an opaque call that may be
reading '%x') to before it.</pre>
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