[LLVMbugs] [Bug 18614] New: Enable the use of TBAA in CodeGen

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18614

            Bug ID: 18614
           Summary: Enable the use of TBAA in CodeGen
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: hfinkel at anl.gov
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

In r200093, I disabled the use of TBAA in CodeGen, because of underlying
correctness issues. Specifically:

  1. Stack coloring does not update TBAA when merging allocas. This is easy
     enough to fix, but is not the largest problem.

  2. CGP inserts ptrtoint/inttoptr pairs when sinking address computations.
Because BasicAA does not handle inttoptr, we'll often miss basic type punning
idioms that we need to catch so we don't miscompile real-world code (like
LLVM).

This second issue is the primary blocker, and can break self hosting (among
other things), especially when misched=shuffle is used.

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