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Bug 1109 - basicaa returns noalias for aliasing pointers, miscompiles MiBench/consumer-typeset
Summary: basicaa returns noalias for aliasing pointers, miscompiles MiBench/consumer-t...
Status: RESOLVED FIXED
Alias: None
Product: libraries
Classification: Unclassified
Component: Global Analyses (show other bugs)
Version: 1.0
Hardware: All All
: P normal
Assignee: Chris Lattner
URL:
Keywords: miscompilation
Depends on:
Blocks:
 
Reported: 2007-01-13 23:46 PST by Chris Lattner
Modified: 2010-02-22 12:47 PST (History)
1 user (show)

See Also:
Fixed By Commit(s):

Attachments
failing testcase (1.64 KB, text/plain)
2007-01-13 23:47 PST, Chris Lattner 		Details
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Description Chris Lattner 2007-01-13 23:46:03 PST 
In the attached heavily reduced testcase, basicaa returns noaa for two pointers that overlap.  This causes 
miscompilation of consumer-typeset.

-Chris
Comment 1 Chris Lattner 2007-01-13 23:47:07 PST 
Created attachment 559 [details]
failing testcase

This performs a bogus xform:
$ llvm-as < t.ll | opt -load-vn -gcse | llvm-dis

The pointers obviously alias at codegen level:

$ llvm-as < t.ll | llc
Comment 2 Chris Lattner 2007-01-13 23:58:48 PST 
Fixed.  Testcase here: Analysis/BasicAA/2007-01-13-BasePointerBadNoAlias.ll

Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070108/042647.html

-Chris