Fix compiler builtin usage in new pg_bitutils.c

Split out these new functions in three parts: one in a new file that
uses the compiler builtin and gets compiled with the -mpopcnt compiler
option if it exists; another one that uses the compiler builtin but not
the compiler option; and finally the fallback with open-coded
algorithms.

Split out the configure logic: in the original commit, it was selecting
to use the -mpopcnt compiler switch together with deciding whether to
use the compiler builtin, but those two things are really separate.
Split them out.  Also, expose whether the builtin exists to
Makefile.global, so that src/port's Makefile can decide whether to
compile the hw-optimized file.

Remove CPUID test for CTZ/CLZ.  Make pg_{right,left}most_ones use either
the compiler intrinsic or open-coded algo; trying to use the
HW-optimized version is a waste of time.  Make them static inline
functions.

Discussion: https://postgr.es/m/20190213221719.GA15976@alvherre.pgsql

1 files changed, 53 insertions, 13 deletions

diff --git a/configure b/configure
index 73e9c235b6..2e3cc372a6 100755
--- a/configure
+++ b/configure
@@ -651,7 +651,7 @@ CFLAGS_ARMV8_CRC32C
 CFLAGS_SSE42
 have_win32_dbghelp
 LIBOBJS
-CFLAGS_POPCNT
+have__builtin_popcount
 UUID_LIBS
 LDAP_LIBS_BE
 LDAP_LIBS_FE
@@ -733,6 +733,7 @@ CPP
 BITCODE_CXXFLAGS
 BITCODE_CFLAGS
 CFLAGS_VECTOR
+CFLAGS_POPCNT
 PERMIT_DECLARATION_AFTER_STATEMENT
 LLVM_BINPATH
 LLVM_CXXFLAGS
@@ -6581,6 +6582,48 @@ fi
 
 fi
 
+# Optimization flags and options for bit-twiddling
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -mpopcnt, for CFLAGS_POPCNT" >&5
+$as_echo_n "checking whether ${CC} supports -mpopcnt, for CFLAGS_POPCNT... " >&6; }
+if ${pgac_cv_prog_CC_cflags__mpopcnt+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS_POPCNT} -mpopcnt"
+ac_save_c_werror_flag=$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_CC_cflags__mpopcnt=yes
+else
+  pgac_cv_prog_CC_cflags__mpopcnt=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: $pgac_cv_prog_CC_cflags__mpopcnt" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__mpopcnt" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__mpopcnt" = x"yes"; then
+  CFLAGS_POPCNT="${CFLAGS_POPCNT} -mpopcnt"
+fi
+
+
+
+
 CFLAGS_VECTOR=$CFLAGS_VECTOR
 
 
@@ -14111,32 +14154,28 @@ $as_echo "#define HAVE__BUILTIN_CTZ 1" >>confdefs.h
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_popcount" >&5
 $as_echo_n "checking for __builtin_popcount... " >&6; }
-if ${pgac_cv_popcount+:} false; then :
+if ${pgac_cv__builtin_popcount+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  pgac_save_CFLAGS=$CFLAGS
-CFLAGS="$pgac_save_CFLAGS -mpopcnt"
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 static int x = __builtin_popcount(255);
+
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
-  pgac_cv_popcount=yes
+  pgac_cv__builtin_popcount=yes
 else
-  pgac_cv_popcount=no
+  pgac_cv__builtin_popcount=no
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-CFLAGS="$pgac_save_CFLAGS"
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_popcount" >&5
-$as_echo "$pgac_cv_popcount" >&6; }
-if test x"$pgac_cv_popcount" = x"yes"; then
-  CFLAGS_POPCNT="-mpopcnt"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_popcount" >&5
+$as_echo "$pgac_cv__builtin_popcount" >&6; }
+if test x"$pgac_cv__builtin_popcount" = x"yes"; then
 
 $as_echo "#define HAVE__BUILTIN_POPCOUNT 1" >>confdefs.h
 
 fi
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_unreachable" >&5
 $as_echo_n "checking for __builtin_unreachable... " >&6; }
 if ${pgac_cv__builtin_unreachable+:} false; then :
@@ -14654,6 +14693,7 @@ $as_echo "#define LOCALE_T_IN_XLOCALE 1" >>confdefs.h
 
 fi
 
+have__builtin_popcount=$pgac_cv__builtin_popcount
 
 
 # MSVC doesn't cope well with defining restrict to __restrict, the