[LLVMbugs] [Bug 17409] New: llvm::SpillPlacement::addLinks takes all the time with asan or msan and -O2

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17409

            Bug ID: 17409
           Summary: llvm::SpillPlacement::addLinks takes all the time with
                    asan or msan and -O2
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: kcc at google.com
                CC: llvmbugs at cs.uiuc.edu, stoklund at 2pi.dk
    Classification: Unclassified

This is a continuation of http://llvm.org/bugs/show_bug.cgi?id=12653
and to some extent related to http://llvm.org/bugs/show_bug.cgi?id=12652
Linux x86_64, r191651 (fresh trunk)

We have a large auto-generated (from protobuffers) C++ code, 
which takes too long to compile at -O2 with asan or msan instrumentation. 
Most of the time is taken by llvm::SpillPlacement::addLinks

The reproducer is too large to attach here: it is attached to 
https://b.corp.google.com/viewIssue?id=5993523#ISSUE_HistoryHeader10

for opt in "-O0"  "-O1" "-O2" "-O2 -fsanitize=address" "-O2 -fsanitize=memory";
do 
  echo ================ $opt =============; 
  (time perf record -f -- clang $opt -c 1000.cc) 2>&1
   perf report 2>&1 | grep "%" | head -5;
done 

================ -O0 =============
TIME: real: 7.350; user: 4.990; system: 0.260
     3.45%  clang-3.3  clang-3.3            [.]
clang::CFGReverseBlockReachabilityAnalysis::mapReachability(clang::CFGBlock
const*)
..
================ -O1 =============
TIME: real: 13.761; user: 13.390; system: 0.210
...
================ -O2 =============
TIME: real: 38.358; user: 37.320; system: 0.790
     3.36%  clang-3.3  clang-3.3            [.]
llvm::ValueHandleBase::RemoveFromUseList()
...
================ -O2 -fsanitize=address =============

TIME: real: 196.757; user: 194.500; system: 1.230
    41.30%  clang-3.3  clang-3.3            [.]
llvm::SpillPlacement::addLinks(llvm::ArrayRef<unsigned int>)
     6.11%  clang-3.3  clang-3.3            [.] (anonymous
namespace)::InlineSpiller::propagateSiblingValue(llvm::DenseMapIterator<llvm::VNInfo*,
(anonymous namespace)::InlineSpiller::SibValueInfo,
llvm::DenseMapInfo<llvm::VNInfo*>, false>, llvm::VNInfo*)
...
================ -O2 -fsanitize=memory =============
TIME: real: 409.187; user: 405.200; system: 2.050
    34.22%  clang-3.3  clang-3.3            [.]
llvm::SpillPlacement::addLinks(llvm::ArrayRef<unsigned int>)
    14.12%  clang-3.3  clang-3.3            [.] (anonymous
namespace)::InlineSpiller::propagateSiblingValue(llvm::DenseMapIterator<llvm::VNInfo*,
(anonymous namespace)::InlineSpiller::SibValueInfo,
llvm::DenseMapInfo<llvm::VNInfo*>, false>, llvm::VNInfo*)
     3.58%  clang-3.3  clang-3.3            [.]
llvm::TinyPtrVector<llvm::VNInfo*>::push_back(llvm::VNInfo*)
...

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