Horton

Re: JIT compiling with LLVM v9.0

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2018-01-26T19:38:17Z
Lists: pgsql-hackers 
Hi,

On 2018-01-26 13:06:27 +0300, Konstantin Knizhnik wrote:
> One more question: do you have any idea how to profile JITed code?

Yes ;). It depends a bit on what exactly you want to do. Is it
sufficient to get time associated with the parent caller, or do you need
instruction-level access.


> There is no LLVMOrcRegisterPerf in LLVM 5, so jit_profiling_support option
> does nothing.

Right, it's a patch I'm trying to get into the next version of
llvm. With that you get access to the shared object and everything.


> And without it perf is not able to unwind stack trace for generated
> code.

You can work around that by using --call-graph lbr with a sufficiently
new perf. That'll not know function names et al, but at least the parent
will be associated correctly.


> But you are compiling code using LLVMOrcAddEagerlyCompiledIR
> and I find no way to pass no-omit-frame pointer option here.

It shouldn't be too hard to open code support for it, encapsulated in a
function:
    // Set function attribute "no-frame-pointer-elim" based on
    // NoFramePointerElim.
    for (auto &F : *Mod) {
      auto Attrs = F.getAttributes();
      StringRef Value(options.NoFramePointerElim ? "true" : "false");
      Attrs = Attrs.addAttribute(F.getContext(), AttributeList::FunctionIndex,
                                 "no-frame-pointer-elim", Value);
      F.setAttributes(Attrs);
    }
that's all that option did for mcjit.

Greetings,

Andres Freund

Commits

  1. Improve JIT docs.

  2. Add documentation for the JIT feature.

  3. Add EXPLAIN support for JIT.

  4. Add inlining support to LLVM JIT provider.

  5. JIT tuple deforming in LLVM JIT provider.

  6. Add FIELDNO_* macro designating offset into structs required for JIT.

  7. Add expression compilation support to LLVM JIT provider.

  8. Expand list of synchronized types and functions in LLVM JIT provider.

  9. Add helpers for emitting LLVM IR.

  10. Basic planner and executor integration for JIT.

  11. Debugging and profiling support for LLVM JIT provider.

  12. Support for optimizing and emitting code in LLVM JIT provider.

  13. Add file containing extensions of the LLVM C API.

  14. Basic JIT provider and error handling infrastructure.

  15. Add configure infrastructure (--with-llvm) to enable LLVM support.

  16. Add C++ support to configure.

  17. Add PGAC_PROG_VARCC_VARFLAGS_OPT autoconf macro.

  18. Fix VM buffer pin management in heap_lock_updated_tuple_rec().

  19. Allow tupleslots to have a fixed tupledesc, use in executor nodes.

  20. Expression evaluation based aggregate transition invocation.

  21. Perform slot validity checks in a separate pass over expression.

  22. Rely on executor utils to build targetlist for DML RETURNING.

  23. Refer to OS X as "macOS", except for the port name which is still "darwin".