[LLVMbugs] [Bug 4791] New: PassMananger can't use alternate AliasAnalysis with GVN

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4791

           Summary: PassMananger can't use alternate AliasAnalysis with GVN
           Product: libraries
           Version: trunk
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Core LLVM classes
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: gohman at apple.com
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=3380)
 --> (http://llvm.org/bugs/attachment.cgi?id=3380)
a testcase in which GVN makes some alias queries

Running a custom alias analysis doesn't work with GVN, even when PR3323 isn't
apparently involved.

Running opt on the attached testcase like this:

  opt -scev-aa -gvn -debug-pass=Structure test.bc

(-scev-aa is a new alias analysis pass in svn) results in this output:

Pass Arguments:  -domtree -loops -scalar-evolution -scev-aa -memdep -gvn
-preverify -verify
Target Data Layout
Basic Alias Analysis (default AA impl)
  ModulePass Manager
    FunctionPass Manager
      Dominator Tree Construction
      Natural Loop Information
      Scalar Evolution Analysis
      ScalarEvolution-based Alias Analysis
      Memory Dependence Analysis
      Global Value Numbering
      Preliminary module verification
      Module Verifier

>From this, it would seem that alias queries in Memory Dependence Analysis
should go to ScalarEvolution-based Alias Analysis, and the problem in
PR3323 isn't present. However, in a debugger, I find that the queries are
going straight to the BasicAliasAnalysis.


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