[llvm] r336419 - CallGraphSCCPass: iterate over all functions.

Evgenii Stepanov via llvm-commits llvm-commits at lists.llvm.org
Fri Jul 13 08:23:59 PDT 2018


MSan buildbot crashes are still happening, once per 8 builds or so. I can't
reproduce them locally and am not 100% sure that this is the change, but,
given the nondeterminism detected on the other bot, I'm going to
tentatively revert it.


On Thu, Jul 12, 2018 at 12:01 PM, Galina Kistanova <gkistanova at gmail.com>
wrote:

> Hello Tim,
>
> This commit has introduced nondeterminism. Please see
> http://lab.llvm.org:8011/builders/clang-with-thin-lto-ubuntu or
> http://lab.llvm.org:8011/builders/clang-with-lto-ubuntu build bots.
>
> This is in addition to those other problems mentioned already, or maybe
> some of the other problems are exposed because of this.
>
> Since the problem is around for quite long now, maybe it worth reverting
> till you will figure out what's wrong and how to fix it?
>
> Thanks
>
> Galina
>
>
>
>
> On Tue, Jul 10, 2018 at 1:33 PM, Evgenii Stepanov via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Hi Tim,
>>
>> MSan bootstrap bot has been randomly crashing lately with the following
>> trace:
>>
>> 3. Running pass 'CallGraph Pass Manager' on module
>> '/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm/lib/Tar
>> get/Hexagon/HexagonCommonGEP.cpp'.
>> #0 0x00005602f79f5cfa llvm::sys::PrintStackTrace(llvm::raw_ostream&)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x24f5cfa)
>> #1 0x00005602f79f42c5 llvm::sys::RunSignalHandlers()
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x24f42c5)
>> #2 0x00005602f79f43dc SignalHandler(int) (/b/sanitizer-x86_64-linux-boo
>> tstrap-msan/build/llvm_build0/bin/clang-7+0x24f43dc)
>> #3 0x00007f63daa840c0 __restore_rt (/lib/x86_64-linux-gnu/libpthr
>> ead.so.0+0x110c0)
>> #4 0x00005602f6edf38e llvm::scc_iterator<llvm::CallGraph*,
>> llvm::GraphTraits<llvm::CallGraph*> >::DFSVisitChildren()
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x19df38e)
>> #5 0x00005602f6edf5aa llvm::scc_iterator<llvm::CallGraph*,
>> llvm::GraphTraits<llvm::CallGraph*> >::GetNextSCC()
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x19df5aa)
>> #6 0x00005602f6ee05ed (anonymous namespace)::CGPassManager::runOnModule(llvm::Module&)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x19e05ed)
>> #7 0x00005602f74ca5fd llvm::legacy::PassManagerImpl::run(llvm::Module&)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x1fca5fd)
>> #8 0x00005602f7bde5c1 (anonymous namespace)::EmitAssemblyHelper
>> ::EmitAssembly(clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream,
>> std::default_delete<llvm::raw_pwrite_stream> >)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x26de5c1)
>> #9 0x00005602f7bdfdf0 clang::EmitBackendOutput(clang::DiagnosticsEngine&,
>> clang::HeaderSearchOptions const&, clang::CodeGenOptions const&,
>> clang::TargetOptions const&, clang::LangOptions const&, llvm::DataLayout
>> const&, llvm::Module*, clang::BackendAction, std::unique_ptr<llvm::raw_pwrite_stream,
>> std::default_delete<llvm::raw_pwrite_stream> >)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x26dfdf0)
>> #10 0x00005602f836f264 clang::BackendConsumer::Handle
>> TranslationUnit(clang::ASTContext&) (/b/sanitizer-x86_64-linux-boo
>> tstrap-msan/build/llvm_build0/bin/clang-7+0x2e6f264)
>> #11 0x00005602f8b37fa9 clang::ParseAST(clang::Sema&, bool, bool)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x3637fa9)
>> #12 0x00005602f836e4d9 clang::CodeGenAction::ExecuteAction()
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x2e6e4d9)
>> #13 0x00005602f800da7e clang::FrontendAction::Execute()
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x2b0da7e)
>> #14 0x00005602f7fd9496 clang::CompilerInstance::Execu
>> teAction(clang::FrontendAction&) (/b/sanitizer-x86_64-linux-boo
>> tstrap-msan/build/llvm_build0/bin/clang-7+0x2ad9496)
>> #15 0x00005602f80ad511 clang::ExecuteCompilerInvocation(clang::CompilerInstance*)
>> (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0x2bad511)
>> #16 0x00005602f614c080 cc1_main(llvm::ArrayRef<char const*>, char const*,
>> void*) (/b/sanitizer-x86_64-linux-bootstrap-msan/build/llvm_build0/
>> bin/clang-7+0xc4c080)
>> #17 0x00005602f60c1a22 main (/b/sanitizer-x86_64-linux-boo
>> tstrap-msan/build/llvm_build0/bin/clang-7+0xbc1a22)
>> #18 0x00007f63d98312e1 __libc_start_main (/lib/x86_64-linux-gnu/libc.so
>> .6+0x202e1)
>> #19 0x00005602f61480aa _start (/b/sanitizer-x86_64-linux-boo
>> tstrap-msan/build/llvm_build0/bin/clang-7+0xc480aa)
>> clang-7: error: unable to execute command: Segmentation fault
>>
>> The crash happens roughly in 1 out of 5-to-10 builds, see history here:
>> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-
>> bootstrap-msan?numbuilds=300
>>
>> The earliest it happened was this build at r336432:
>> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-
>> bootstrap-msan/builds/5763
>>
>> I suspect that this change could be the culprit. Could you take a look?
>>
>>
>> On Fri, Jul 6, 2018 at 1:04 AM, Tim Northover via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: tnorthover
>>> Date: Fri Jul  6 01:04:47 2018
>>> New Revision: 336419
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=336419&view=rev
>>> Log:
>>> CallGraphSCCPass: iterate over all functions.
>>>
>>> Previously we only iterated over functions reachable from the set of
>>> external functions in the module. But since some of the passes under
>>> this (notably the always-inliner and coroutine lowerer) are required for
>>> correctness, they need to run over everything.
>>>
>>> This just adds an extra layer of iteration over the CallGraph to keep
>>> track of which functions we've already visited and get the next batch of
>>> SCCs.
>>>
>>> Should fix PR38029.
>>>
>>> Modified:
>>>     llvm/trunk/include/llvm/ADT/SCCIterator.h
>>>     llvm/trunk/lib/Analysis/CallGraphSCCPass.cpp
>>>     llvm/trunk/test/Transforms/Inline/always-inline.ll
>>>
>>> Modified: llvm/trunk/include/llvm/ADT/SCCIterator.h
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/
>>> ADT/SCCIterator.h?rev=336419&r1=336418&r2=336419&view=diff
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/include/llvm/ADT/SCCIterator.h (original)
>>> +++ llvm/trunk/include/llvm/ADT/SCCIterator.h Fri Jul  6 01:04:47 2018
>>> @@ -90,6 +90,7 @@ class scc_iterator : public iterator_fac
>>>    /// Compute the next SCC using the DFS traversal.
>>>    void GetNextSCC();
>>>
>>> +public:
>>>    scc_iterator(NodeRef entryN) : visitNum(0) {
>>>      DFSVisitOne(entryN);
>>>      GetNextSCC();
>>> @@ -98,12 +99,6 @@ class scc_iterator : public iterator_fac
>>>    /// End is when the DFS stack is empty.
>>>    scc_iterator() = default;
>>>
>>> -public:
>>> -  static scc_iterator begin(const GraphT &G) {
>>> -    return scc_iterator(GT::getEntryNode(G));
>>> -  }
>>> -  static scc_iterator end(const GraphT &) { return scc_iterator(); }
>>> -
>>>    /// Direct loop termination test which is more efficient than
>>>    /// comparison with \c end().
>>>    bool isAtEnd() const {
>>> @@ -222,16 +217,25 @@ bool scc_iterator<GraphT, GT>::hasLoop()
>>>      return false;
>>>    }
>>>
>>> -/// Construct the begin iterator for a deduced graph type T.
>>> +/// Construct the begin iterator for a deduced graph type T, starting
>>> from its
>>> +/// entry node.
>>>  template <class T> scc_iterator<T> scc_begin(const T &G) {
>>> -  return scc_iterator<T>::begin(G);
>>> +  return scc_iterator<T>(GraphTraits<T>::getEntryNode(G));
>>>  }
>>>
>>> -/// Construct the end iterator for a deduced graph type T.
>>> +/// Construct the begin iterator for a graph type T, starting from the
>>> specified
>>> +/// node.
>>> +template <class T, class U = GraphTraits<T>>
>>> +scc_iterator<T, U> scc_begin(typename U::NodeRef N) {
>>> +  return scc_iterator<T>(N);
>>> +}
>>> +
>>> +  /// Construct the end iterator for a deduced graph type T.
>>>  template <class T> scc_iterator<T> scc_end(const T &G) {
>>> -  return scc_iterator<T>::end(G);
>>> +  return scc_iterator<T>();
>>>  }
>>>
>>> +
>>>  } // end namespace llvm
>>>
>>>  #endif // LLVM_ADT_SCCITERATOR_H
>>>
>>> Modified: llvm/trunk/lib/Analysis/CallGraphSCCPass.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/
>>> CallGraphSCCPass.cpp?rev=336419&r1=336418&r2=336419&view=diff
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Analysis/CallGraphSCCPass.cpp (original)
>>> +++ llvm/trunk/lib/Analysis/CallGraphSCCPass.cpp Fri Jul  6 01:04:47
>>> 2018
>>> @@ -17,6 +17,7 @@
>>>
>>>  #include "llvm/Analysis/CallGraphSCCPass.h"
>>>  #include "llvm/ADT/DenseMap.h"
>>> +#include "llvm/ADT/DenseSet.h"
>>>  #include "llvm/ADT/SCCIterator.h"
>>>  #include "llvm/ADT/Statistic.h"
>>>  #include "llvm/Analysis/CallGraph.h"
>>> @@ -63,6 +64,10 @@ public:
>>>    /// whether any of the passes modifies the module, and if so, return
>>> true.
>>>    bool runOnModule(Module &M) override;
>>>
>>> +  /// Execute all of the passes scheduled for execution on a given SCC.
>>> Return
>>> +  /// true if any passes modify the module.
>>> +  bool runOnSCC(CallGraphSCC &SCC, CallGraph &CG);
>>> +
>>>    using ModulePass::doInitialization;
>>>    using ModulePass::doFinalization;
>>>
>>> @@ -448,51 +453,78 @@ bool CGPassManager::RunAllPassesOnSCC(Ca
>>>  bool CGPassManager::runOnModule(Module &M) {
>>>    CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
>>>    bool Changed = doInitialization(CG);
>>> -
>>> -  // Walk the callgraph in bottom-up SCC order.
>>> -  scc_iterator<CallGraph*> CGI = scc_begin(&CG);
>>>
>>> -  CallGraphSCC CurSCC(CG, &CGI);
>>> -  while (!CGI.isAtEnd()) {
>>> -    // Copy the current SCC and increment past it so that the pass can
>>> hack
>>> -    // on the SCC if it wants to without invalidating our iterator.
>>> -    const std::vector<CallGraphNode *> &NodeVec = *CGI;
>>> -    CurSCC.initialize(NodeVec);
>>> -    ++CGI;
>>> -
>>> -    // At the top level, we run all the passes in this pass manager on
>>> the
>>> -    // functions in this SCC.  However, we support iterative
>>> compilation in the
>>> -    // case where a function pass devirtualizes a call to a function.
>>> For
>>> -    // example, it is very common for a function pass (often GVN or
>>> instcombine)
>>> -    // to eliminate the addressing that feeds into a call.  With that
>>> improved
>>> -    // information, we would like the call to be an inline candidate,
>>> infer
>>> -    // mod-ref information etc.
>>> -    //
>>> -    // Because of this, we allow iteration up to a specified iteration
>>> count.
>>> -    // This only happens in the case of a devirtualized call, so we
>>> only burn
>>> -    // compile time in the case that we're making progress.  We also
>>> have a hard
>>> -    // iteration count limit in case there is crazy code.
>>> -    unsigned Iteration = 0;
>>> -    bool DevirtualizedCall = false;
>>> -    do {
>>> -      LLVM_DEBUG(if (Iteration) dbgs()
>>> -                 << "  SCCPASSMGR: Re-visiting SCC, iteration #" <<
>>> Iteration
>>> -                 << '\n');
>>> -      DevirtualizedCall = false;
>>> -      Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
>>> -    } while (Iteration++ < MaxIterations && DevirtualizedCall);
>>> -
>>> -    if (DevirtualizedCall)
>>> -      LLVM_DEBUG(dbgs() << "  CGSCCPASSMGR: Stopped iteration after "
>>> -                        << Iteration
>>> -                        << " times, due to -max-cg-scc-iterations\n");
>>> +  DenseSet<const Function *> Visited;
>>>
>>> -    MaxSCCIterations.updateMax(Iteration);
>>> +  CallGraph::iterator INext;
>>> +  for (auto I = CG.begin(), E = CG.end(); I != E;) {
>>> +    // Walk the callgraph in bottom-up SCC order.
>>> +    auto CGI = scc_begin<CallGraph *>(I->second.get());
>>> +
>>> +    CallGraphSCC CurSCC(CG, &CGI);
>>> +    while (!CGI.isAtEnd()) {
>>> +      const std::vector<CallGraphNode *> &NodeVec = *CGI;
>>> +
>>> +      // Record that we've seen this set of functions so we don't run
>>> the pass
>>> +      // twice.
>>> +      for (auto *Elt : NodeVec)
>>> +        Visited.insert(Elt->getFunction());
>>> +
>>> +      // Copy the current SCC and increment past it so that the pass
>>> can hack
>>> +      // on the SCC if it wants to without invalidating our iterator.
>>> +      CurSCC.initialize(NodeVec);
>>> +      ++CGI;
>>> +
>>> +      // If we've got all functions reachable from our chosen initial
>>> node,
>>> +      // calculate the next node we need to search from now before
>>> parts of the
>>> +      // graph are invalidated.
>>> +      if (CGI.isAtEnd()) {
>>> +        do
>>> +          ++I;
>>> +        while (I != E && Visited.count(I->first));
>>> +      }
>>> +
>>> +      Changed |= runOnSCC(CurSCC, CG);
>>> +    }
>>>    }
>>> +
>>>    Changed |= doFinalization(CG);
>>>    return Changed;
>>>  }
>>>
>>> +bool CGPassManager::runOnSCC(CallGraphSCC &CurSCC, CallGraph &CG) {
>>> +  bool Changed = false;
>>> +
>>> +  // At the top level, we run all the passes in this pass manager on the
>>> +  // functions in this SCC.  However, we support iterative compilation
>>> in the
>>> +  // case where a function pass devirtualizes a call to a function.  For
>>> +  // example, it is very common for a function pass (often GVN or
>>> instcombine)
>>> +  // to eliminate the addressing that feeds into a call.  With that
>>> improved
>>> +  // information, we would like the call to be an inline candidate,
>>> infer
>>> +  // mod-ref information etc.
>>> +  //
>>> +  // Because of this, we allow iteration up to a specified iteration
>>> count.
>>> +  // This only happens in the case of a devirtualized call, so we only
>>> burn
>>> +  // compile time in the case that we're making progress.  We also have
>>> a hard
>>> +  // iteration count limit in case there is crazy code.
>>> +  unsigned Iteration = 0;
>>> +  bool DevirtualizedCall = false;
>>> +  do {
>>> +    LLVM_DEBUG(if (Iteration) dbgs()
>>> +               << "  SCCPASSMGR: Re-visiting SCC, iteration #" <<
>>> Iteration
>>> +               << '\n');
>>> +    DevirtualizedCall = false;
>>> +    Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
>>> +  } while (Iteration++ < MaxIterations && DevirtualizedCall);
>>> +
>>> +  if (DevirtualizedCall)
>>> +    LLVM_DEBUG(dbgs() << "  CGSCCPASSMGR: Stopped iteration after " <<
>>> Iteration
>>> +                      << " times, due to -max-cg-scc-iterations\n");
>>> +
>>> +  MaxSCCIterations.updateMax(Iteration);
>>> +  return Changed;
>>> +}
>>> +
>>>  /// Initialize CG
>>>  bool CGPassManager::doInitialization(CallGraph &CG) {
>>>    bool Changed = false;
>>>
>>> Modified: llvm/trunk/test/Transforms/Inline/always-inline.ll
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transfor
>>> ms/Inline/always-inline.ll?rev=336419&r1=336418&r2=336419&view=diff
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/test/Transforms/Inline/always-inline.ll (original)
>>> +++ llvm/trunk/test/Transforms/Inline/always-inline.ll Fri Jul  6
>>> 01:04:47 2018
>>> @@ -316,3 +316,10 @@ define void @outer14() {
>>>    call void @inner14()
>>>    ret void
>>>  }
>>> +
>>> +define internal i32 @outer15() {
>>> +; CHECK-LABEL: @outer15
>>> +; CHECK: ret i32 1
>>> +  %res = call i32 @inner1()
>>> +  ret i32 %res
>>> +}
>>>
>>>
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>>> llvm-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>
>>
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