jit: Use opaque pointers in all supported LLVM versions.

LLVM's opaque pointer change began in LLVM 14, but remained optional
until LLVM 16.  When commit 37d5babb added opaque pointer support, we
didn't turn it on for LLVM 14 and 15 yet because we didn't want to risk
weird bitcode incompatibility problems in released branches of
PostgreSQL.  (That might have been overly cautious, I don't know.)

Now that PostgreSQL 18 has dropped support for LLVM versions < 14, and
since it hasn't been released yet and no extensions or bitcode have been
built against it in the wild yet, we can be more aggressive.  We can rip
out the support code and build system clutter that made opaque pointer
use optional.

Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussions: https://postgr.es/m/CA%2BhUKGLhNs5geZaVNj2EJ79Dx9W8fyWUU3HxcpZy55sMGcY%3DiA%40mail.gmail.com

configure

@@ -7281,95 +7281,6 @@ if test x"$pgac_cv_prog_CLANGXX_cxxflags__fexcess_precision_standard" = x"yes";
 fi
 
 
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANG} supports -Xclang -no-opaque-pointers, for BITCODE_CFLAGS" >&5
-$as_echo_n "checking whether ${CLANG} supports -Xclang -no-opaque-pointers, for BITCODE_CFLAGS... " >&6; }
-if ${pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  pgac_save_CFLAGS=$CFLAGS
-pgac_save_CC=$CC
-CC=${CLANG}
-CFLAGS="${BITCODE_CFLAGS} -Xclang -no-opaque-pointers"
-ac_save_c_werror_flag=$ac_c_werror_flag
-ac_c_werror_flag=yes
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers=yes
-else
-  pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-ac_c_werror_flag=$ac_save_c_werror_flag
-CFLAGS="$pgac_save_CFLAGS"
-CC="$pgac_save_CC"
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers" >&5
-$as_echo "$pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers" >&6; }
-if test x"$pgac_cv_prog_CLANG_cflags__Xclang__no_opaque_pointers" = x"yes"; then
-  BITCODE_CFLAGS="${BITCODE_CFLAGS} -Xclang -no-opaque-pointers"
-fi
-
-  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANGXX} supports -Xclang -no-opaque-pointers, for BITCODE_CXXFLAGS" >&5
-$as_echo_n "checking whether ${CLANGXX} supports -Xclang -no-opaque-pointers, for BITCODE_CXXFLAGS... " >&6; }
-if ${pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  pgac_save_CXXFLAGS=$CXXFLAGS
-pgac_save_CXX=$CXX
-CXX=${CLANGXX}
-CXXFLAGS="${BITCODE_CXXFLAGS} -Xclang -no-opaque-pointers"
-ac_save_cxx_werror_flag=$ac_cxx_werror_flag
-ac_cxx_werror_flag=yes
-ac_ext=cpp
-ac_cpp='$CXXCPP $CPPFLAGS'
-ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
-
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-int
-main ()
-{
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_cxx_try_compile "$LINENO"; then :
-  pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers=yes
-else
-  pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-ac_ext=c
-ac_cpp='$CPP $CPPFLAGS'
-ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
-ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
-ac_compiler_gnu=$ac_cv_c_compiler_gnu
-
-ac_cxx_werror_flag=$ac_save_cxx_werror_flag
-CXXFLAGS="$pgac_save_CXXFLAGS"
-CXX="$pgac_save_CXX"
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers" >&5
-$as_echo "$pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers" >&6; }
-if test x"$pgac_cv_prog_CLANGXX_cxxflags__Xclang__no_opaque_pointers" = x"yes"; then
-  BITCODE_CXXFLAGS="${BITCODE_CXXFLAGS} -Xclang -no-opaque-pointers"
-fi
-
-
   NOT_THE_CFLAGS=""
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANG} supports -Wunused-command-line-argument, for NOT_THE_CFLAGS" >&5
 $as_echo_n "checking whether ${CLANG} supports -Wunused-command-line-argument, for NOT_THE_CFLAGS... " >&6; }

configure.ac

@@ -631,9 +631,6 @@ if test "$with_llvm" = yes ; then
   PGAC_PROG_VARCC_VARFLAGS_OPT(CLANG, BITCODE_CFLAGS, [-fexcess-precision=standard])
   PGAC_PROG_VARCXX_VARFLAGS_OPT(CLANGXX, BITCODE_CXXFLAGS, [-fexcess-precision=standard])
 
-  PGAC_PROG_VARCC_VARFLAGS_OPT(CLANG, BITCODE_CFLAGS, [-Xclang -no-opaque-pointers])
-  PGAC_PROG_VARCXX_VARFLAGS_OPT(CLANGXX, BITCODE_CXXFLAGS, [-Xclang -no-opaque-pointers])
-
   NOT_THE_CFLAGS=""
   PGAC_PROG_VARCC_VARFLAGS_OPT(CLANG, NOT_THE_CFLAGS, [-Wunused-command-line-argument])
   if test -n "$NOT_THE_CFLAGS"; then

src/backend/jit/llvm/llvmjit.c

@@ -840,19 +840,6 @@ llvm_session_initialize(void)
 		llvm_llvm_context_reuse_count = 0;
 	}
 
-	/*
-	 * When targeting LLVM 15, turn off opaque pointers for the context we
-	 * build our code in.  We don't need to do so for other contexts (e.g.
-	 * llvm_ts_context).  Once the IR is generated, it carries the necessary
-	 * information.
-	 *
-	 * For 16 and above, opaque pointers must be used, and we have special
-	 * code for that.
-	 */
-#if LLVM_VERSION_MAJOR == 15
-	LLVMContextSetOpaquePointers(LLVMGetGlobalContext(), false);
-#endif
-
 	/*
 	 * Synchronize types early, as that also includes inferring the target
 	 * triple.

src/backend/jit/llvm/meson.build

@@ -60,9 +60,6 @@ endif
 
 # XXX: Need to determine proper version of the function cflags for clang
 bitcode_cflags = ['-fno-strict-aliasing', '-fwrapv']
-if llvm.version().version_compare('=15.0')
-  bitcode_cflags += ['-Xclang', '-no-opaque-pointers']
-endif
 bitcode_cflags += get_option('c_args')
 bitcode_cflags += cppflags
 

src/include/jit/llvmjit_emit.h

@@ -107,41 +107,25 @@ l_pbool_const(bool i)
 static inline LLVMValueRef
 l_struct_gep(LLVMBuilderRef b, LLVMTypeRef t, LLVMValueRef v, int32 idx, const char *name)
 {
-#if LLVM_VERSION_MAJOR < 16
-	return LLVMBuildStructGEP(b, v, idx, "");
-#else
 	return LLVMBuildStructGEP2(b, t, v, idx, "");
-#endif
 }
 
 static inline LLVMValueRef
 l_gep(LLVMBuilderRef b, LLVMTypeRef t, LLVMValueRef v, LLVMValueRef *indices, int32 nindices, const char *name)
 {
-#if LLVM_VERSION_MAJOR < 16
-	return LLVMBuildGEP(b, v, indices, nindices, name);
-#else
 	return LLVMBuildGEP2(b, t, v, indices, nindices, name);
-#endif
 }
 
 static inline LLVMValueRef
 l_load(LLVMBuilderRef b, LLVMTypeRef t, LLVMValueRef v, const char *name)
 {
-#if LLVM_VERSION_MAJOR < 16
-	return LLVMBuildLoad(b, v, name);
-#else
 	return LLVMBuildLoad2(b, t, v, name);
-#endif
 }
 
 static inline LLVMValueRef
 l_call(LLVMBuilderRef b, LLVMTypeRef t, LLVMValueRef fn, LLVMValueRef *args, int32 nargs, const char *name)
 {
-#if LLVM_VERSION_MAJOR < 16
-	return LLVMBuildCall(b, fn, args, nargs, name);
-#else
 	return LLVMBuildCall2(b, t, fn, args, nargs, name);
-#endif
 }
 
 /*