+# Check for LTO support.
+AC_ARG_ENABLE(lto,
+[ --enable-lto enable link time optimization support],
+enable_lto=$enableval,
+enable_lto=yes; default_enable_lto=yes)
+
+if test x"$enable_lto" = x"yes" ; then
+ # Make sure that libelf.h and gelf.h are available.
+ AC_ARG_WITH(libelf, [ --with-libelf=PATH Specify prefix directory for the installed libelf package
+ Equivalent to --with-libelf-include=PATH/include
+ plus --with-libelf-lib=PATH/lib])
+
+ AC_ARG_WITH(libelf_include, [ --with-libelf-include=PATH Specify directory for installed libelf include files])
+
+ AC_ARG_WITH(libelf_lib, [ --with-libelf-lib=PATH Specify the directory for the installed libelf library])
+
+ case $with_libelf in
+ "")
+ libelflibs="-lelf"
+ libelfinc="-I/usr/include/libelf"
+ ;;
+ *)
+ libelflibs="-L$with_libelf/lib -lelf"
+ libelfinc="-I$with_libelf/include -I$with_libelf/include/libelf"
+ LIBS="$libelflibs $LIBS"
+ ;;
+ esac
+
+ if test "x$with_libelf_include" != x; then
+ libelfinc="-I$with_libelf_include"
+ fi
+
+ if test "x$with_libelf_lib" != x; then
+ libelflibs="-L$with_libelf_lib -lelf"
+ LIBS="$libelflibs $LIBS"
+ fi
+
+ if test "x$with_libelf$with_libelf_include$with_libelf_lib" = x \
+ && test -d ${srcdir}/libelf; then
+ libelflibs='-L$$r/$(HOST_SUBDIR)/libelf/.libs -L$$r/$(HOST_SUBDIR)/libelf/_libs -lelf '
+ libelfinc='-I$$r/$(HOST_SUBDIR)/libelf/include -I$$s/libelf/include'
+ LIBS="$libelflibs $LIBS"
+ fi
+
+ saved_CFLAGS="$CFLAGS"
+ saved_CPPFLAGS="$CPPFLAGS"
+ saved_LIBS="$LIBS"
+
+ CFLAGS="$CFLAGS $libelfinc"
+ CPPFLAGS="$CPPFLAGS $libelfinc"
+ LIBS="$LIBS $libelflibs"
+
+ AC_CHECK_HEADERS(libelf.h, [have_libelf_h=yes])
+ AC_CHECK_HEADERS(gelf.h, [have_gelf_h=yes])
+
+ AC_CHECK_HEADERS(libelf/libelf.h, [have_libelf_libelf_h=yes])
+ AC_CHECK_HEADERS(libelf/gelf.h, [have_libelf_gelf_h=yes])
+
+ # If we couldn't find libelf.h and the user forced it, emit an error.
+ if test x"$have_libelf_h" != x"yes" \
+ && test x"$have_libelf_libelf_h" != x"yes" ; then
+ if test x"$default_enable_lto" != x"yes" ; then
+ AC_MSG_ERROR([LTO support requires libelf.h or libelf/libelf.h.])
+ else
+ enable_lto=no
+ libelflibs=
+ libelfinc=
+ fi
+ fi
+
+ # If we couldn't find gelf.h and the user forced it, emit an error.
+ if test x"$have_gelf_h" != x"yes" \
+ && test x"$have_libelf_gelf_h" != x"yes" ; then
+ if test x"$default_enable_lto" != x"yes" ; then
+ AC_MSG_ERROR([LTO support requires gelf.h or libelf/gelf.h.])
+ else
+ enable_lto=no
+ libelflibs=
+ libelfinc=
+ fi
+ fi
+
+ # Check that the detected libelf has the functions we need. We cannot
+ # rely on just detecting the headers since they do not include
+ # versioning information. Add functions, if needed.
+ if test x"$enable_lto" = x"yes" ; then
+ AC_MSG_CHECKING([for the correct version of libelf])
+ AC_TRY_LINK(
+ [#include <libelf.h>],[
+ elf_errmsg (0);
+ elf_getscn (0, 0);
+ elf_nextscn (0, 0);
+ elf_strptr (0, 0, 0);
+ elf_getident (0, 0);
+ elf_getshdrstrndx (0, 0);
+ elf_begin (0, 0, 0);
+ elf_ndxscn (0);
+ elf_end (0);
+ ],
+ [AC_MSG_RESULT([yes]);],
+ [AC_MSG_RESULT([no]); enable_lto=no; libelflibs= ; libelfinc= ]
+ )
+
+ # If we couldn't enable LTO and the user forced it, emit an error.
+ if test x"$enable_lto" = x"no" \
+ && test x"$default_enable_lto" != x"yes" ; then
+ AC_MSG_ERROR([To enable LTO, GCC requires libelf v0.8.12+.
+Try the --with-libelf, --with-libelf-include and --with-libelf-lib options
+to specify its location.])
+ fi
+ fi
+
+ CFLAGS="$saved_CFLAGS"
+ CPPFLAGS="$saved_CPPFLAGS"
+ LIBS="$saved_LIBS"
+
+ # Flags needed for libelf.
+ AC_SUBST(libelflibs)
+ AC_SUBST(libelfinc)
+fi
+