https://bugs.gentoo.org/924757 https://bugs.gentoo.org/926891 https://github.com/tesseract-ocr/tesseract/pull/4154 (Note that if moving to CMake, can use the patch from ghostscript-gpl instead, i.e. https://src.fedoraproject.org/rpms/tesseract/blob/rawhide/f/tesseract_neon.patch). From b1e48789d61d995740762f66f505385db42410a5 Mon Sep 17 00:00:00 2001 From: Jan Palus Date: Mon, 30 Oct 2023 01:36:57 +0100 Subject: [PATCH] Check if NEON extension are actually available User may pass own compiler flags to configure which override those provided by project through automake. Therefore it is possible for user on ARM platform to pass CXXFLAGS=-mfpu=vfp which will effectively disable NEON even though used compiler supports -mfpu=neon (since user supplied flags take precedence compiler invocation will use flags: -mfpu=neon -mfpu=vfp). Instead of checking whether compiler supports -mfpu=neon flag, check if NEON extensions are available by checking if __ARM_NEON is defined when compiling with -mfpu=neon and user supplied flags combined. Signed-off-by: Jan Palus --- configure.ac | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/configure.ac b/configure.ac index 0b38537229..0514b619c5 100644 --- a/configure.ac +++ b/configure.ac @@ -178,10 +178,20 @@ case "${host_cpu}" in ;; arm*) - - AX_CHECK_COMPILE_FLAG([-mfpu=neon], [neon=true], [neon=false], [$WERROR]) - AM_CONDITIONAL([HAVE_NEON], $neon) - if $neon; then + SAVE_CXXFLAGS="$CXXFLAGS" + CXXFLAGS="-mfpu=neon $CXXFLAGS" + AC_MSG_CHECKING([for NEON support]) + AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM([], [[ + #ifndef __ARM_NEON + #error + #endif + ]])], + [neon=yes], [neon=no]) + AC_MSG_RESULT([$neon]) + CXXFLAGS="$SAVE_CXXFLAGS" + AM_CONDITIONAL([HAVE_NEON], test "xyes" = "x$neon") + if test "xyes" = "$neon"; then AC_DEFINE([HAVE_NEON], [1], [Enable NEON instructions]) NEON_CXXFLAGS="-mfpu=neon" AC_SUBST([NEON_CXXFLAGS])