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Basic JIT provider and error handling infrastructure.
This commit introduces: 1) JIT provider abstraction, which allows JIT functionality to be implemented in separate shared libraries. That's desirable because it allows to install JIT support as a separate package, and because it allows experimentation with different forms of JITing. 2) JITContexts which can be, using functions introduced in follow up commits, used to emit JITed functions, and have them be cleaned up on error. 3) The outline of a LLVM JIT provider, which will be fleshed out in subsequent commits. Documentation for GUCs added, and for JIT in general, will be added in later commits. Author: Andres Freund, with architectural input from Jeff Davis Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de
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‎src/Makefile‎

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@@ -31,6 +31,10 @@ SUBDIRS = \
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test/isolation \
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test/perl
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ifeq ($(with_llvm), yes)
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SUBDIRS += backend/jit/llvm
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endif
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# There are too many interdependencies between the subdirectories, so
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# don't attempt parallel make here.
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.NOTPARALLEL:

‎src/backend/Makefile‎

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@@ -19,7 +19,8 @@ include $(top_builddir)/src/Makefile.global
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SUBDIRS = access bootstrap catalog parser commands executor foreign lib libpq \
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main nodes optimizer port postmaster regex replication rewrite \
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statistics storage tcop tsearch utils $(top_builddir)/src/timezone
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statistics storage tcop tsearch utils $(top_builddir)/src/timezone \
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jit
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include $(srcdir)/common.mk
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‎src/backend/jit/Makefile‎

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#-------------------------------------------------------------------------
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#
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# Makefile--
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# Makefile for JIT code that's provider independent.
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#
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# Note that the LLVM JIT provider is recursed into by src/Makefile,
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# not from here.
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#
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# IDENTIFICATION
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# src/backend/jit/Makefile
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#
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#-------------------------------------------------------------------------
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subdir = src/backend/jit
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top_builddir = ../../..
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include $(top_builddir)/src/Makefile.global
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override CPPFLAGS += -DDLSUFFIX=\"$(DLSUFFIX)\"
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OBJS = jit.o
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include $(top_srcdir)/src/backend/common.mk

‎src/backend/jit/jit.c‎

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/*-------------------------------------------------------------------------
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*
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* jit.c
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* Provider independent JIT infrastructure.
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*
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* Code related to loading JIT providers, redirecting calls into JIT providers
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* and error handling. No code specific to a specific JIT implementation
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* should end up here.
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*
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*
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* Copyright (c) 2016-2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/backend/jit/jit.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "fmgr.h"
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#include "jit/jit.h"
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#include "miscadmin.h"
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#include "utils/resowner_private.h"
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#include "utils/fmgrprotos.h"
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/* GUCs */
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bool jit_enabled = true;
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char *jit_provider = "llvmjit";
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static JitProviderCallbacks provider;
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static bool provider_successfully_loaded = false;
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static bool provider_failed_loading = false;
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static bool provider_init(void);
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static bool file_exists(const char *name);
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/*
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* SQL level function returning whether JIT is available in the current
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* backend. Will attempt to load JIT provider if necessary.
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*/
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Datum
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pg_jit_available(PG_FUNCTION_ARGS)
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{
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PG_RETURN_BOOL(provider_init());
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}
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/*
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* Return whether a JIT provider has successfully been loaded, caching the
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* result.
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*/
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static bool
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provider_init(void)
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{
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char path[MAXPGPATH];
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JitProviderInit init;
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/* don't even try to load if not enabled */
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if (!jit_enabled)
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return false;
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/*
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* Don't retry loading after failing - attempting to load JIT provider
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* isn't cheap.
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*/
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if (provider_failed_loading)
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return false;
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if (provider_successfully_loaded)
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return true;
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/*
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* Check whether shared library exists. We do that check before actually
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* attempting to load the shared library (via load_external_function()),
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* because that'd error out in case the shlib isn't available.
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*/
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snprintf(path, MAXPGPATH, "%s/%s%s", pkglib_path, jit_provider, DLSUFFIX);
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elog(DEBUG1, "probing availability of JIT provider at %s", path);
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if (!file_exists(path))
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{
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elog(DEBUG1,
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"provider not available, disabling JIT for current session");
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provider_failed_loading = true;
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return false;
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}
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/*
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* If loading functions fails, signal failure. We do so because
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* load_external_function() might error out despite the above check if
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* e.g. the library's dependencies aren't installed. We want to signal
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* ERROR in that case, so the user is notified, but we don't want to
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* continually retry.
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*/
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provider_failed_loading = true;
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/* and initialize */
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init = (JitProviderInit)
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load_external_function(path, "_PG_jit_provider_init", true, NULL);
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init(&provider);
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provider_successfully_loaded = true;
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provider_failed_loading = false;
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elog(DEBUG1, "successfully loaded JIT provider in current session");
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return true;
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}
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/*
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* Reset JIT provider's error handling. This'll be called after an error has
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* been thrown and the main-loop has re-established control.
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*/
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void
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jit_reset_after_error(void)
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{
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if (provider_successfully_loaded)
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provider.reset_after_error();
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}
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/*
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* Release resources required by one JIT context.
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*/
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void
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jit_release_context(JitContext *context)
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{
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if (provider_successfully_loaded)
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provider.release_context(context);
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ResourceOwnerForgetJIT(context->resowner, PointerGetDatum(context));
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pfree(context);
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}
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static bool
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file_exists(const char *name)
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{
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struct stat st;
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AssertArg(name != NULL);
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if (stat(name, &st) == 0)
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return S_ISDIR(st.st_mode) ? false : true;
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else if (!(errno == ENOENT || errno == ENOTDIR))
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not access file \"%s\": %m", name)));
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return false;
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}

‎src/backend/jit/llvm/Makefile‎

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#-------------------------------------------------------------------------
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#
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# Makefile--
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# Makefile the LLVM JIT provider, building it into a shared library.
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#
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# Note that this file is recursed into from src/Makefile, not by the
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# parent directory..
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#
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# IDENTIFICATION
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# src/backend/jit/llvm/Makefile
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#
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#-------------------------------------------------------------------------
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subdir = src/backend/jit/llvm
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top_builddir = ../../../..
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include $(top_builddir)/src/Makefile.global
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ifneq ($(with_llvm), yes)
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$(error "not building with LLVM support")
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endif
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PGFILEDESC = "llvmjit - JIT using LLVM"
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NAME = llvmjit
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# All files in this directy use LLVM.
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CFLAGS += $(LLVM_CFLAGS)
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CXXFLAGS += $(LLVM_CXXFLAGS)
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override CPPFLAGS := $(LLVM_CPPFLAGS) $(CPPFLAGS)
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SHLIB_LINK += $(LLVM_LIBS)
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SHLIB_PREREQS += submake-generated-headers
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# Because this module includes C++ files, we need to use a C++
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# compiler for linking. Makefile.shlib uses $(COMPILER) to build
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# loadable modules.
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override COMPILER = $(CXX) $(CFLAGS)
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OBJS=$(WIN32RES)
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# Infrastructure
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OBJS += llvmjit.o llvmjit_error.o
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# Code generation
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OBJS +=
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all: all-shared-lib
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install: all installdirs install-lib
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installdirs: installdirs-lib
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uninstall: uninstall-lib
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include $(top_srcdir)/src/Makefile.shlib
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clean distclean maintainer-clean: clean-lib
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rm -f $(OBJS)

‎src/backend/jit/llvm/llvmjit.c‎

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/*-------------------------------------------------------------------------
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*
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* llvmjit.c
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* Core part of the LLVM JIT provider.
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*
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* Copyright (c) 2016-2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/backend/jit/llvm/llvmjit.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "jit/llvmjit.h"
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#include "miscadmin.h"
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#include "utils/memutils.h"
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#include "utils/resowner_private.h"
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#include "storage/ipc.h"
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#include <llvm-c/Target.h>
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static bool llvm_session_initialized = false;
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static void llvm_release_context(JitContext *context);
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static void llvm_session_initialize(void);
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static void llvm_shutdown(int code, Datum arg);
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PG_MODULE_MAGIC;
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/*
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* Initialize LLVM JIT provider.
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*/
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void
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_PG_jit_provider_init(JitProviderCallbacks *cb)
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{
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cb->reset_after_error = llvm_reset_after_error;
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cb->release_context = llvm_release_context;
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}
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/*
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* Create a context for JITing work.
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*
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* The context, including subsidiary resources, will be cleaned up either when
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* the context is explicitly released, or when the lifetime of
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* CurrentResourceOwner ends (usually the end of the current [sub]xact).
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*/
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LLVMJitContext *
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llvm_create_context(int jitFlags)
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{
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LLVMJitContext *context;
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llvm_assert_in_fatal_section();
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llvm_session_initialize();
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ResourceOwnerEnlargeJIT(CurrentResourceOwner);
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context = MemoryContextAllocZero(TopMemoryContext,
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sizeof(LLVMJitContext));
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context->base.flags = jitFlags;
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/* ensure cleanup */
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context->base.resowner = CurrentResourceOwner;
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ResourceOwnerRememberJIT(CurrentResourceOwner, PointerGetDatum(context));
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return context;
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}
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/*
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* Release resources required by one llvm context.
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*/
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static void
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llvm_release_context(JitContext *context)
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{
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}
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/*
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* Per session initialization.
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*/
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static void
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llvm_session_initialize(void)
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{
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MemoryContext oldcontext;
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if (llvm_session_initialized)
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return;
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oldcontext = MemoryContextSwitchTo(TopMemoryContext);
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LLVMInitializeNativeTarget();
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LLVMInitializeNativeAsmPrinter();
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LLVMInitializeNativeAsmParser();
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before_shmem_exit(llvm_shutdown, 0);
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llvm_session_initialized = true;
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MemoryContextSwitchTo(oldcontext);
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}
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static void
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llvm_shutdown(int code, Datum arg)
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{
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}

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