jit: Drop redundant LLVM configure probes.

We currently require LLVM 14, so these probes for LLVM 9 functions
always succeeded.  Even when the features aren't enabled in an LLVM
build, dummy functions are defined (a problem for a later commit).

The whole PGAC_CHECK_LLVM_FUNCTIONS macro and Meson equivalent are
removed, because we switched to testing LLVM_VERSION_MAJOR at compile
time in subsequent work and these were the last holdouts.  That suits
the nature of LLVM API evolution better, and also allows for strictly
mechanical pruning in future commits like 820b5af7 and 972c2cd2.  They
advanced the minimum LLVM version but failed to spot these.

Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA%2BhUKGJgB6gvrdDohgwLfCwzVQm%3DVMtb9m0vzQn%3DCwWn-kwG9w%40mail.gmail.com

config/llvm.m4

@@ -101,20 +101,3 @@ dnl LLVM_CONFIG, CLANG are already output via AC_ARG_VAR
   AC_SUBST(LLVM_BINPATH)
 
 ])# PGAC_LLVM_SUPPORT
-
-
-# PGAC_CHECK_LLVM_FUNCTIONS
-# -------------------------
-#
-# Check presence of some optional LLVM functions.
-# (This shouldn't happen until we're ready to run AC_CHECK_DECLS tests;
-# because PGAC_LLVM_SUPPORT runs very early, it's not an appropriate place.)
-#
-AC_DEFUN([PGAC_CHECK_LLVM_FUNCTIONS],
-[
-  # Check which functionality is present
-  SAVE_CPPFLAGS="$CPPFLAGS"
-  CPPFLAGS="$CPPFLAGS $LLVM_CPPFLAGS"
-  AC_CHECK_DECLS([LLVMCreateGDBRegistrationListener, LLVMCreatePerfJITEventListener], [], [], [[#include <llvm-c/ExecutionEngine.h>]])
-  CPPFLAGS="$SAVE_CPPFLAGS"
-])# PGAC_CHECK_LLVM_FUNCTIONS

configure

@@ -16607,38 +16607,6 @@ fi
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
-if test "$with_llvm" = yes; then
-
-  # Check which functionality is present
-  SAVE_CPPFLAGS="$CPPFLAGS"
-  CPPFLAGS="$CPPFLAGS $LLVM_CPPFLAGS"
-  ac_fn_c_check_decl "$LINENO" "LLVMCreateGDBRegistrationListener" "ac_cv_have_decl_LLVMCreateGDBRegistrationListener" "#include <llvm-c/ExecutionEngine.h>
-"
-if test "x$ac_cv_have_decl_LLVMCreateGDBRegistrationListener" = xyes; then :
-  ac_have_decl=1
-else
-  ac_have_decl=0
-fi
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER $ac_have_decl
-_ACEOF
-ac_fn_c_check_decl "$LINENO" "LLVMCreatePerfJITEventListener" "ac_cv_have_decl_LLVMCreatePerfJITEventListener" "#include <llvm-c/ExecutionEngine.h>
-"
-if test "x$ac_cv_have_decl_LLVMCreatePerfJITEventListener" = xyes; then :
-  ac_have_decl=1
-else
-  ac_have_decl=0
-fi
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE_DECL_LLVMCREATEPERFJITEVENTLISTENER $ac_have_decl
-_ACEOF
-
-  CPPFLAGS="$SAVE_CPPFLAGS"
-
-fi
-
 # Lastly, restore full LIBS list and check for readline/libedit symbols
 LIBS="$LIBS_including_readline"
 

configure.ac

@@ -1941,10 +1941,6 @@ if test "$with_icu" = yes; then
   CPPFLAGS=$ac_save_CPPFLAGS
 fi
 
-if test "$with_llvm" = yes; then
-  PGAC_CHECK_LLVM_FUNCTIONS()
-fi
-
 # Lastly, restore full LIBS list and check for readline/libedit symbols
 LIBS="$LIBS_including_readline"
 

meson.build

@@ -2679,14 +2679,6 @@ decl_checks += [
   ['memset_s', 'string.h', '#define __STDC_WANT_LIB_EXT1__ 1'],
 ]
 
-# Check presence of some optional LLVM functions.
-if llvm.found()
-  decl_checks += [
-    ['LLVMCreateGDBRegistrationListener', 'llvm-c/ExecutionEngine.h'],
-    ['LLVMCreatePerfJITEventListener', 'llvm-c/ExecutionEngine.h'],
-  ]
-endif
-
 foreach c : decl_checks
   func = c.get(0)
   header = c.get(1)

src/backend/jit/llvm/llvmjit.c

@@ -1180,24 +1180,19 @@ llvm_create_object_layer(void *Ctx, LLVMOrcExecutionSessionRef ES, const char *T
 		LLVMOrcCreateRTDyldObjectLinkingLayerWithSectionMemoryManager(ES);
 #endif
 
-
-#if defined(HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER) && HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER
 	if (jit_debugging_support)
 	{
 		LLVMJITEventListenerRef l = LLVMCreateGDBRegistrationListener();
 
 		LLVMOrcRTDyldObjectLinkingLayerRegisterJITEventListener(objlayer, l);
 	}
-#endif
 
-#if defined(HAVE_DECL_LLVMCREATEPERFJITEVENTLISTENER) && HAVE_DECL_LLVMCREATEPERFJITEVENTLISTENER
 	if (jit_profiling_support)
 	{
 		LLVMJITEventListenerRef l = LLVMCreatePerfJITEventListener();
 
 		LLVMOrcRTDyldObjectLinkingLayerRegisterJITEventListener(objlayer, l);
 	}
-#endif
 
 	return objlayer;
 }

src/include/pg_config.h.in

@@ -83,14 +83,6 @@
    don't. */
 #undef HAVE_DECL_F_FULLFSYNC
 
-/* Define to 1 if you have the declaration of
-   `LLVMCreateGDBRegistrationListener', and to 0 if you don't. */
-#undef HAVE_DECL_LLVMCREATEGDBREGISTRATIONLISTENER
-
-/* Define to 1 if you have the declaration of
-   `LLVMCreatePerfJITEventListener', and to 0 if you don't. */
-#undef HAVE_DECL_LLVMCREATEPERFJITEVENTLISTENER
-
 /* Define to 1 if you have the declaration of `memset_s', and to 0 if you
    don't. */
 #undef HAVE_DECL_MEMSET_S