[LLVMdev] How to transfer AliasAnalysis result from a module pass to a function pass?

[Shen Liu]

Hi all,

I am Shen, a new LLVM learner. Now i am trying to call basic alias analysis
in my own module pass, i hope to use -basicaa to check whether two pointers
are aliases in the inner function passes.

After I run the command *opt -load  ./pdg.so -basicaa -dot-pdg
-debug-pass=Structure < $1 > /dev/null*

the compiler reports as follows:

Pass Arguments:  -targetlibinfo -datalayout -notti -basictti -x86tti -no-aa
-basicaa -pdg -dot-pdg -verify -verify-di
Target Library Information
Data Layout
No target information
Target independent code generator's TTI
X86 Target Transform Info
*No Alias Analysis (always returns 'may' alias)*
*Basic Alias Analysis (stateless AA impl)*
  ModulePass Manager
    Program Dependency Graph
      Unnamed pass: implement Pass::getPassName()
    FunctionPass Manager
      Print instruction-level program dependency graph of function to 'dot'
file
      Module Verifier
    Debug Info Verifier
    Bitcode Writer
Pass Arguments:  -no-aa -fda
*No Alias Analysis (always returns 'may' alias)*
  FunctionPass Manager
    Flow  Dependence Analysis

If all passes are Function pass, -basicaa can be executed very well. But
when I call -basicaa through a Module pass. It seems the basic AA was
called during the runtime. However, the inner function pass didn't see
-basicaa option but use default -no-aa instead.

So is there a good way to let my inner Function pass get the result from
outer Module pass?

Best regards,

Shen
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