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/[email protected]

3 files changed, 72 insertions, 0 deletions

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 153373ead02..afb1007842a 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -42,6 +42,7 @@
 #include "commands/variable.h"
 #include "commands/trigger.h"
 #include "funcapi.h"
+#include "jit/jit.h"
 #include "libpq/auth.h"
 #include "libpq/libpq.h"
 #include "libpq/pqformat.h"
@@ -1714,6 +1715,16 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"jit", PGC_USERSET, QUERY_TUNING_OTHER,
+			gettext_noop("Allow JIT compilation."),
+			NULL
+		},
+		&jit_enabled,
+		true,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL
@@ -3707,6 +3718,17 @@ static struct config_string ConfigureNamesString[] =
 		check_wal_consistency_checking, assign_wal_consistency_checking, NULL
 	},
 
+	{
+		{"jit_provider", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("JIT provider to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&jit_provider,
+		"llvmjit",
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 048bf4cccd7..91eacacdc97 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -606,6 +606,8 @@
 
 #dynamic_library_path = '$libdir'
 
+#jit = on				# allow JIT compilation
+#jit_provider = 'llvmjit'		# JIT implementation to use
 
 #------------------------------------------------------------------------------
 # LOCK MANAGEMENT
diff --git a/src/backend/utils/resowner/resowner.c b/src/backend/utils/resowner/resowner.c
index e09a4f1ddb4..bce021e1001 100644
--- a/src/backend/utils/resowner/resowner.c
+++ b/src/backend/utils/resowner/resowner.c
@@ -21,6 +21,7 @@
 #include "postgres.h"
 
 #include "access/hash.h"
+#include "jit/jit.h"
 #include "storage/predicate.h"
 #include "storage/proc.h"
 #include "utils/memutils.h"
@@ -124,6 +125,7 @@ typedef struct ResourceOwnerData
 	ResourceArray snapshotarr;	/* snapshot references */
 	ResourceArray filearr;		/* open temporary files */
 	ResourceArray dsmarr;		/* dynamic shmem segments */
+	ResourceArray jitarr;		/* JIT contexts */
 
 	/* We can remember up to MAX_RESOWNER_LOCKS references to local locks. */
 	int			nlocks;			/* number of owned locks */
@@ -437,6 +439,7 @@ ResourceOwnerCreate(ResourceOwner parent, const char *name)
 	ResourceArrayInit(&(owner->snapshotarr), PointerGetDatum(NULL));
 	ResourceArrayInit(&(owner->filearr), FileGetDatum(-1));
 	ResourceArrayInit(&(owner->dsmarr), PointerGetDatum(NULL));
+	ResourceArrayInit(&(owner->jitarr), PointerGetDatum(NULL));
 
 	return owner;
 }
@@ -538,6 +541,14 @@ ResourceOwnerReleaseInternal(ResourceOwner owner,
 				PrintDSMLeakWarning(res);
 			dsm_detach(res);
 		}
+
+		/* Ditto for JIT contexts */
+		while (ResourceArrayGetAny(&(owner->jitarr), &foundres))
+		{
+			JitContext *context = (JitContext *) PointerGetDatum(foundres);
+
+			jit_release_context(context);
+		}
 	}
 	else if (phase == RESOURCE_RELEASE_LOCKS)
 	{
@@ -685,6 +696,7 @@ ResourceOwnerDelete(ResourceOwner owner)
 	Assert(owner->snapshotarr.nitems == 0);
 	Assert(owner->filearr.nitems == 0);
 	Assert(owner->dsmarr.nitems == 0);
+	Assert(owner->jitarr.nitems == 0);
 	Assert(owner->nlocks == 0 || owner->nlocks == MAX_RESOWNER_LOCKS + 1);
 
 	/*
@@ -711,6 +723,7 @@ ResourceOwnerDelete(ResourceOwner owner)
 	ResourceArrayFree(&(owner->snapshotarr));
 	ResourceArrayFree(&(owner->filearr));
 	ResourceArrayFree(&(owner->dsmarr));
+	ResourceArrayFree(&(owner->jitarr));
 
 	pfree(owner);
 }
@@ -1253,3 +1266,38 @@ PrintDSMLeakWarning(dsm_segment *seg)
 	elog(WARNING, "dynamic shared memory leak: segment %u still referenced",
 		 dsm_segment_handle(seg));
 }
+
+/*
+ * Make sure there is room for at least one more entry in a ResourceOwner's
+ * JIT context reference array.
+ *
+ * This is separate from actually inserting an entry because if we run out of
+ * memory, it's critical to do so *before* acquiring the resource.
+ */
+void
+ResourceOwnerEnlargeJIT(ResourceOwner owner)
+{
+	ResourceArrayEnlarge(&(owner->jitarr));
+}
+
+/*
+ * Remember that a JIT context is owned by a ResourceOwner
+ *
+ * Caller must have previously done ResourceOwnerEnlargeJIT()
+ */
+void
+ResourceOwnerRememberJIT(ResourceOwner owner, Datum handle)
+{
+	ResourceArrayAdd(&(owner->jitarr), handle);
+}
+
+/*
+ * Forget that a JIT context is owned by a ResourceOwner
+ */
+void
+ResourceOwnerForgetJIT(ResourceOwner owner, Datum handle)
+{
+	if (!ResourceArrayRemove(&(owner->jitarr), handle))
+		elog(ERROR, "JIT context %p is not owned by resource owner %s",
+			 DatumGetPointer(handle), owner->name);
+}