[llvm-dev] Slow IR compilation/JIT, profiling points to LLVM?

[edA-qa mort-ora-y via llvm-dev]

I'm having issues of my compiler, and JIT execution, of LLVM IR being
rather slow. It's accounting for the vast majority of my full
compilation time.  I'm trying to figure out why this is happening, since
it's becoming an impediment.  (Note: by slow I mean about 3s of time for
only about 2K of my front-end code, 65K lines of LLVM-IR)


Using valgrind I see some functions which seem out of place and
accounting for the vast majority of the time.

    5.72%; 635,008 Calls; llvm::PMTopLevelManager::findAnalysisPass(void
const*) <cycle 4>

    4.54%; 3,722,489 Calls; llvm::PMDataManager::findAnalysisPass(void
const*, bool)'2

    4.11%; 4,604,499 Calls; bool
llvm::DenseMapBase<>::LookupBucketFor<>(void const* const&,
llvm::detail::DenseMapPair<> const*&) const

Also of interest, given the high call count:

    1.32%; 6,915,882 Calls; llvm::FoldingSetNodeID::AddInteger(unsigned
int) <cycle 4>

The call counts seem quite high given the size of the code. Also, the
`findAnalysisPass` function just seems off, but I don't understand
LLVM's architecture to be sure.


Could this be pointing to something I'm doing wrong in my LLVM setup, or
is it just slow?


I'm reasonably certain I'm compiling LLVM in optimized mode, but for
reference, this is my build line:

    cmake .. -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_EH=ON
-DLLVM_ENABLE_RTTI=ON -DLLVM_REQUIRES_RTTI=ON -DLLVM_ENABLE_CXX1Y=ON
-DLLVM_LINK_LLVM_DYLIB=ON -DLLVM_ENABLE_FFI=ON
-DLLVM_ENABLE_ASSERTIONS=ON -DLLVM_OPTIMIZED_TABLEGEN=ON
-DCMAKE_INSTALL_PREFIX="/opt/llvm/install"


The overall time split, from valgrind, between shared libraries in my
code is:

    80.48%, libLLVM-6.0.so
    8.83% libc-2.23.so
    2.34% libleaf_lang.so (my front-end)

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