Improve our method for probing the availability of ARM CRC instructions.

Instead of depending on glibc's getauxval() function, just try to execute
the CRC code, and trap SIGILL if that happens.

Thomas Munro

Discussion: https://postgr.es/m/HE1PR0801MB1323D171938EABC04FFE7FA9E3110@HE1PR0801MB1323.eurprd08.prod.outlook.com

1 files changed, 2 insertions, 43 deletions

diff --git a/configure b/configure
index 56f18dfbc26..0aafd9c8c06 100755
--- a/configure
+++ b/configure
@@ -17344,46 +17344,6 @@ fi
 fi
 
 
-# In order to detect at runtime, if the ARM CRC Extension is available,
-# we will do "getauxval(AT_HWCAP) & HWCAP_CRC32". Check if we have
-# everything we need for that.
-for ac_func in getauxval
-do :
-  ac_fn_c_check_func "$LINENO" "getauxval" "ac_cv_func_getauxval"
-if test "x$ac_cv_func_getauxval" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_GETAUXVAL 1
-_ACEOF
-
-fi
-done
-
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-#include <sys/auxv.h>
-#include <asm/hwcap.h>
-
-int
-main ()
-{
-
-#ifndef AT_HWCAP
-#error AT_HWCAP not defined
-#endif
-#ifndef HWCAP_CRC32
-#error HWCAP_CRC32 not defined
-#endif
-
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  HAVE_HWCAP_CRC32=1
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-
 # Select CRC-32C implementation.
 #
 # If we are targeting a processor that has Intel SSE 4.2 instructions, we can
@@ -17414,9 +17374,8 @@ if test x"$USE_SLICING_BY_8_CRC32C" = x"" && test x"$USE_SSE42_CRC32C" = x"" &&
       if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$CFLAGS_ARMV8_CRC32C" = x""; then
         USE_ARMV8_CRC32C=1
       else
-        # ARM CRC Extension, with runtime check? The getauxval() function and
-        # HWCAP_CRC32 are needed for the runtime check.
-        if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$ac_cv_func_getauxval" = x"yes" && test x"$HAVE_HWCAP_CRC32" = x"1"; then
+        # ARM CRC Extension, with runtime check?
+        if test x"$pgac_armv8_crc32c_intrinsics" = x"yes"; then
           USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK=1
         else
           # fall back to slicing-by-8 algorithm, which doesn't require any