Horton

Re: JIT compiling with LLVM v12.2

Catalin Iacob <iacobcatalin@gmail.com>

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From: Catalin Iacob <iacobcatalin@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Stephen Frost <sfrost@snowman.net>, Thomas Munro <thomas.munro@enterprisedb.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-21T07:26:28Z
Lists: pgsql-hackers 
On Wed, Mar 21, 2018 at 4:07 AM, Andres Freund <andres@anarazel.de> wrote:
> Indeed. I've pushed a rebased version now, that basically just fixes the
> issue Thomas observed.

Testing 2d6f2fba from your repository configured --with-llvm I noticed
some weird things in the configure output.

Without --enable-debug:
configure: using compiler=gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)
configure: using CFLAGS=-Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -fexcess-precision=standard -O2
configure: using CPPFLAGS= -D_GNU_SOURCE
configure: using LDFLAGS= -L/opt/rh/llvm-toolset-7/root/usr/lib64
-Wl,--as-needed
configure: using CXX=g++
configure: using CXXFLAGS=-Wall -Wpointer-arith -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -g -O2
configure: using CLANG=/opt/rh/llvm-toolset-7/root/usr/bin/clang
configure: using BITCODE_CFLAGS= -fno-strict-aliasing -fwrapv -O2
configure: using BITCODE_CXXFLAGS= -fno-strict-aliasing -fwrapv -O2
BITCODE_CXXFLAGS

With --enable-debug:
configure: using compiler=gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16)
configure: using CFLAGS=-Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -fexcess-precision=standard -g -O2
configure: using CPPFLAGS= -D_GNU_SOURCE
configure: using LDFLAGS= -L/opt/rh/llvm-toolset-7/root/usr/lib64
-Wl,--as-needed
configure: using CXX=g++
configure: using CXXFLAGS=-Wall -Wpointer-arith -Wendif-labels
-Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
-fwrapv -g -g -O2
configure: using CLANG=/opt/rh/llvm-toolset-7/root/usr/bin/clang
configure: using BITCODE_CFLAGS= -fno-strict-aliasing -fwrapv -O2
configure: using BITCODE_CXXFLAGS= -fno-strict-aliasing -fwrapv -O2
BITCODE_CXXFLAGS

So I unconditionally get one -g added to CXXFLAGS regardless of
whether I specify --enable-debug or not. And --enable-debug results in
-g -g in CXXFLAGS.

Didn't get to look at the code yet, maybe that comes from:
$ llvm-config --cxxflags
-I/opt/rh/llvm-toolset-7/root/usr/include -O2 -g -pipe -Wall
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong
--param=ssp-buffer-size=4 -grecord-gcc-switches   -m64 -mtune=generic
-fPIC -fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter
-Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic
-Wno-long-long -Wno-maybe-uninitialized -Wdelete-non-virtual-dtor
-Wno-comment -std=c++11 -ffunction-sections -fdata-sections -O2 -g
-DNDEBUG  -fno-exceptions -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS
-D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS

But on the other hand there are lots of other flags in there that
don't end up in CXXFLAGS.

BTW, you should probably specify -std=c++11 (or whatever you need) as
various g++ and clang++ versions default to various things. Will the
required C++ standard be based on the requirements of the C++ code in
the PG tree or will you take it from LLVM's CXXFLAGS? Can --std=c++11
and --std=c++14 compiled .o files be linked together? Or in other
words, in case in the future LLVM starts requiring C++14 but the code
in the PG tree you wrote still builds with C++11, will PG upgrade it's
requirement with LLVM or will it stay with the older standard?

Also, my CXXFLAGS did not get -fexcess-precision=standard neither did
BITCODE_CFLAGS nor BITCODE_CXXFLAGS.

In case it's interesting:
$ llvm-config --cflags
-I/opt/rh/llvm-toolset-7/root/usr/include -O2 -g -pipe -Wall
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong
--param=ssp-buffer-size=4 -grecord-gcc-switches   -m64 -mtune=generic
-fPIC -Wall -W -Wno-unused-parameter -Wwrite-strings
-Wno-missing-field-initializers -pedantic -Wno-long-long -Wno-comment
-ffunction-sections -fdata-sections -O2 -g -DNDEBUG -D_GNU_SOURCE
-D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS


2. Unlike all the other *FLAGS, BITCODE_CXXFLAGS includes itself on
the right hand side of the equal
configure: using BITCODE_CXXFLAGS= -fno-strict-aliasing -fwrapv -O2
BITCODE_CXXFLAGS

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".