[llvm-commits] Pass manager bug fix

[Guo, Xiaoyi]

Thank you !

Xiaoyi

From: Andrew Trick [mailto:atrick at apple.com]
Sent: Monday, August 29, 2011 2:25 PM
To: Guo, Xiaoyi
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] Pass manager bug fix

Checked in as r138737.

Thanks for the fix!

-Andy

On Aug 25, 2011, at 3:25 PM, Guo, Xiaoyi wrote:


Please review the attached fix for a problem in the pass manager, and commit if acceptable. The fix is against TOT and has passed regression tests.

The problem is in the assignPassManager() methods. For example, in LoopPass::assignPassManager():

    // Create new Loop Pass Manager if it does not exist.
    assert (!PMS.empty() && "Unable to create Loop Pass Manager");
    PMDataManager *PMD = PMS.top();

    // [1] Create new Call Graph Pass Manager
    LPPM = new LPPassManager();
    LPPM->populateInheritedAnalysis(PMS);

    // [2] Set up new manager's top level manager
    PMTopLevelManager *TPM = PMD->getTopLevelManager();
    TPM->addIndirectPassManager(LPPM);

    // [3] Assign manager to manage this new manager. This may create
    // and push new managers into PMS
    Pass *P = LPPM->getAsPass();
    TPM->schedulePass(P);

    // [4] Push new manager into PMS
    PMS.push(LPPM);


Step 3 above may create and push new managers into PMS, in which case the Depth of LPPM will no longer be correct. This may in turn cause other things to go wrong. For example, it may cause some analysis passes to be freed prematurely and cause crash.

My fix is to not set the depth of a pass manager until it is pushed onto the stack.

Regards,
Xiaoyi
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