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<body><span class="vcard"><a class="email" href="mailto:aschwaighofer@apple.com" title="Arnold Schwaighofer <aschwaighofer@apple.com>"> <span class="fn">Arnold Schwaighofer</span></a>
</span> changed
<a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - LoopVectorizer does not detect that calloc and one of the parameters don't alias"
href="http://llvm.org/bugs/show_bug.cgi?id=14719">bug 14719</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>RESOLVED
</td>
<td>REOPENED
</td>
</tr>
<tr>
<td style="text-align:right;">CC</td>
<td>
</td>
<td>aschwaighofer@apple.com
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>FIXED
</td>
<td>---
</td>
</tr>
<tr>
<td style="text-align:right;">Assignee</td>
<td>unassignedbugs@nondot.org
</td>
<td>aschwaighofer@apple.com
</td>
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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - LoopVectorizer does not detect that calloc and one of the parameters don't alias"
href="http://llvm.org/bugs/show_bug.cgi?id=14719#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - LoopVectorizer does not detect that calloc and one of the parameters don't alias"
href="http://llvm.org/bugs/show_bug.cgi?id=14719">bug 14719</a>
from <span class="vcard"><a class="email" href="mailto:aschwaighofer@apple.com" title="Arnold Schwaighofer <aschwaighofer@apple.com>"> <span class="fn">Arnold Schwaighofer</span></a>
</span></b>
<pre>I just stumbled over this while working on dependence checks.
This is not entirely correct:
/// Check that the reads don't conflict with the read-writes.
for (MI = Reads.begin(), ME = Reads.end(); MI != ME; ++MI) {
Value *Val = (*MI).first;
GetUnderlyingObjects(Val, TempObjects, DL);
for (ValueVector::iterator UI=TempObjects.begin(), UE=TempObjects.end();
UI != UE; ++UI) {
// If all of the writes are identified then we don't care if the read
// pointer is identified or not.
if (!AllWritesIdentified && !isIdentifiedObject(*UI)) {
DEBUG(dbgs() << "LV: Found an unidentified read ptr:"<< **UI <<"\n");
NeedRTCheck = true;
}
We could have GetUnderlying return an unidentified object because it stopped
after MaxSteps and have "A[i] = B[i]" where B == A - 1 (just hidden behind
enough phis).
We would however know that if all our writes are identified objects and the
read is a argument (isa<Argument>, like it is the case here) that they can't
alias.
if ((!AreAllWritesIdentified || !isa<Argument>(UnderlyingObj)) &&
!isIdentifiedObject(UnderlyingObj)) {
NeedRTCheck = true;
}</pre>
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