Debugging and profiling support for LLVM JIT provider.

This currently requires patches to the LLVM codebase to be
effective (submitted upstream), the GUCs are available without those
patches however.

Author: Andres Freund
Discussion: https://postgr.es/m/20170901064131.tazjxwus3k2w3ybh@alap3.anarazel.de

src/backend/jit/jit.c

@@ -33,7 +33,9 @@
 /* GUCs */
 bool		jit_enabled = true;
 char	   *jit_provider = "llvmjit";
+bool		jit_debugging_support = false;
 bool		jit_dump_bitcode = false;
+bool		jit_profiling_support = false;
 
 static JitProviderCallbacks provider;
 static bool provider_successfully_loaded = false;

src/backend/jit/llvm/llvmjit.c

@@ -541,6 +541,21 @@ llvm_session_initialize(void)
 	llvm_opt0_orc = LLVMOrcCreateInstance(llvm_opt0_targetmachine);
 	llvm_opt3_orc = LLVMOrcCreateInstance(llvm_opt3_targetmachine);
 
+#if defined(HAVE_DECL_LLVMORCREGISTERGDB) && HAVE_DECL_LLVMORCREGISTERGDB
+	if (jit_debugging_support)
+	{
+		LLVMOrcRegisterGDB(llvm_opt0_orc);
+		LLVMOrcRegisterGDB(llvm_opt3_orc);
+	}
+#endif
+#if defined(HAVE_DECL_LLVMORCREGISTERPERF) && HAVE_DECL_LLVMORCREGISTERPERF
+	if (jit_profiling_support)
+	{
+		LLVMOrcRegisterPerf(llvm_opt0_orc);
+		LLVMOrcRegisterPerf(llvm_opt3_orc);
+	}
+#endif
+
 	before_shmem_exit(llvm_shutdown, 0);
 
 	llvm_session_initialized = true;
@@ -551,6 +566,27 @@ llvm_session_initialize(void)
 static void
 llvm_shutdown(int code, Datum arg)
 {
+	/* unregister profiling support, needs to be flushed to be useful */
+
+	if (llvm_opt3_orc)
+	{
+#if defined(HAVE_DECL_LLVMORCREGISTERPERF) && HAVE_DECL_LLVMORCREGISTERPERF
+		if (jit_profiling_support)
+			LLVMOrcUnregisterPerf(llvm_opt3_orc);
+#endif
+		LLVMOrcDisposeInstance(llvm_opt3_orc);
+		llvm_opt3_orc = NULL;
+	}
+
+	if (llvm_opt0_orc)
+	{
+#if defined(HAVE_DECL_LLVMORCREGISTERPERF) && HAVE_DECL_LLVMORCREGISTERPERF
+		if (jit_profiling_support)
+			LLVMOrcUnregisterPerf(llvm_opt0_orc);
+#endif
+		LLVMOrcDisposeInstance(llvm_opt0_orc);
+		llvm_opt0_orc = NULL;
+	}
 }
 
 /* helper for llvm_create_types */

src/backend/utils/misc/guc.c

@@ -1734,6 +1734,22 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"jit_debugging_support", PGC_SU_BACKEND, DEVELOPER_OPTIONS,
+			gettext_noop("Register JIT compiled function with debugger."),
+			NULL,
+			GUC_NOT_IN_SAMPLE
+		},
+		&jit_debugging_support,
+		false,
+		/*
+		 * This is not guaranteed to be available, but given it's a developer
+		 * oriented option, it doesn't seem worth adding code checking
+		 * availability.
+		 */
+		NULL, NULL, NULL
+	},
+
 	{
 		{"jit_dump_bitcode", PGC_SUSET, DEVELOPER_OPTIONS,
 			gettext_noop("Write out LLVM bitcode to facilitate JIT debugging."),
@@ -1745,6 +1761,22 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"jit_profiling_support", PGC_SU_BACKEND, DEVELOPER_OPTIONS,
+			gettext_noop("Register JIT compiled function with perf profiler."),
+			NULL,
+			GUC_NOT_IN_SAMPLE
+		},
+		&jit_profiling_support,
+		false,
+		/*
+		 * This is not guaranteed to be available, but given it's a developer
+		 * oriented option, it doesn't seem worth adding code checking
+		 * availability.
+		 */
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL, NULL

src/include/jit/jit.h

@@ -58,7 +58,9 @@ struct JitProviderCallbacks
 /* GUCs */
 extern bool jit_enabled;
 extern char *jit_provider;
+extern bool jit_debugging_support;
 extern bool jit_dump_bitcode;
+extern bool jit_profiling_support;
 
 
 extern void jit_reset_after_error(void);