[LLVMbugs] [Bug 4267] New: BasicAliasAnalysis misanalyzes over-indexed GEP

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4267

           Summary: BasicAliasAnalysis misanalyzes over-indexed GEP
           Product: libraries
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: miscompilation
          Severity: normal
          Priority: P2
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: gohman at apple.com
                CC: llvmbugs at cs.uiuc.edu


Running

  opt -aa-eval -print-all-alias-modref-info

on the attached testcase prints out this:

  NoAlias:      double* %p.0.i.0, double* %p3

This is incorrect because in the second iteration of the loop,
%p.0.i.0 is equal to %p3.

Background: The new indvars GEP reconstruction logic is now emitting
code that does this, and this is resulting in some testcases being
miscompiled. With extra care, indvars could probably avoid
emitting code that triggers this bug in most cases, however it's
a bug regardless.


-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.