Target FP: Make use of MPFR if available

This second patch introduces mfpr_float_ops, an new implementation
of target_float_ops.  This implements precise emulation of target
floating-point formats using the MPFR library.  This is then used
to perform operations on types that do not match any host type.

Note that use of MPFR is still not required.  The patch adds
a configure option --with-mpfr similar to --with-expat.  If use of
MPFR is disabled via the option or MPFR is not available, code will
fall back to current behavior.  This means that operations on types
that do not match any host type will be implemented on the host
long double type instead.

A new test case verifies that we can correctly print the largest
__float128 value now.

gdb/ChangeLog:
2017-11-22  Ulrich Weigand  <uweigand@de.ibm.com>

	* NEWS: Document use of GNU MPFR.
	* README: Likewise.

	* Makefile.in (LIBMPFR): Add define.
	(CLIBS): Add $(LIBMPFR).
	* configure.ac: Add --with-mpfr configure option.
	* configure: Regenerate.
	* config.in: Regenerate.

	* target-float.c [HAVE_LIBMPFR]: Include <mpfr.h>.
	(class mpfr_float_ops): New type.
	(mpfr_float_ops::from_target): Two new overloaded functions.
	(mpfr_float_ops::to_target): Likewise.
	(mpfr_float_ops::to_string): New function.
	(mpfr_float_ops::from_string): Likewise.
	(mpfr_float_ops::to_longest): Likewise.
	(mpfr_float_ops::from_longest): Likewise.
	(mpfr_float_ops::from_ulongest): Likewise.
	(mpfr_float_ops::to_host_double): Likewise.
	(mpfr_float_ops::from_host_double): Likewise.
	(mpfr_float_ops::convert): Likewise.
	(mpfr_float_ops::binop): Likewise.
	(mpfr_float_ops::compare): Likewise.
	(get_target_float_ops): Use mpfr_float_ops if available.

gdb/doc/ChangeLog:
2017-11-22  Ulrich Weigand  <uweigand@de.ibm.com>

	* gdb.texinfo (Requirements): Document use of GNU MPFR.

gdb/testsuite/ChangeLog:
2017-11-22  Ulrich Weigand  <uweigand@de.ibm.com>

	* gdb.base/float128.c (large128): New variable.
	* gdb.base/float128.exp: Add test to print largest __float128 value.

1 files changed, 499 insertions, 0 deletions

diff --git a/gdb/configure b/gdb/configure
index def194d..55544fb 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -682,6 +682,9 @@ PYTHON_LIBS
 PYTHON_CPPFLAGS
 PYTHON_CFLAGS
 python_prog_path
+LTLIBMPFR
+LIBMPFR
+HAVE_LIBMPFR
 LTLIBEXPAT
 LIBEXPAT
 HAVE_LIBEXPAT
@@ -838,6 +841,8 @@ with_system_readline
 with_jit_reader_dir
 with_expat
 with_libexpat_prefix
+with_mpfr
+with_libmpfr_prefix
 with_python
 with_guile
 enable_libmcheck
@@ -1560,6 +1565,9 @@ Optional Packages:
   --with-expat            include expat support (auto/yes/no)
   --with-libexpat-prefix[=DIR]  search for libexpat in DIR/include and DIR/lib
   --without-libexpat-prefix     don't search for libexpat in includedir and libdir
+  --with-mpfr             include MPFR support (auto/yes/no)
+  --with-libmpfr-prefix[=DIR]  search for libmpfr in DIR/include and DIR/lib
+  --without-libmpfr-prefix     don't search for libmpfr in includedir and libdir
   --with-python[=PYTHON]  include python support
                           (auto/yes/no/<python-program>)
   --with-guile[=GUILE]    include guile support
@@ -9643,6 +9651,497 @@ done
   fi
 fi
 
+
+# Check whether --with-mpfr was given.
+if test "${with_mpfr+set}" = set; then :
+  withval=$with_mpfr;
+else
+  with_mpfr=auto
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to use MPFR" >&5
+$as_echo_n "checking whether to use MPFR... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $with_mpfr" >&5
+$as_echo "$with_mpfr" >&6; }
+
+if test "${with_mpfr}" = no; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: MPFR support disabled; some features may be unavailable." >&5
+$as_echo "$as_me: WARNING: MPFR support disabled; some features may be unavailable." >&2;}
+  HAVE_LIBMPFR=no
+else
+
+
+
+
+
+
+
+
+    use_additional=yes
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+
+    eval additional_includedir=\"$includedir\"
+    eval additional_libdir=\"$libdir\"
+
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+
+# Check whether --with-libmpfr-prefix was given.
+if test "${with_libmpfr_prefix+set}" = set; then :
+  withval=$with_libmpfr_prefix;
+    if test "X$withval" = "Xno"; then
+      use_additional=no
+    else
+      if test "X$withval" = "X"; then
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+
+          eval additional_includedir=\"$includedir\"
+          eval additional_libdir=\"$libdir\"
+
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+      else
+        additional_includedir="$withval/include"
+        additional_libdir="$withval/lib"
+      fi
+    fi
+
+fi
+
+      LIBMPFR=
+  LTLIBMPFR=
+  INCMPFR=
+  rpathdirs=
+  ltrpathdirs=
+  names_already_handled=
+  names_next_round='mpfr '
+  while test -n "$names_next_round"; do
+    names_this_round="$names_next_round"
+    names_next_round=
+    for name in $names_this_round; do
+      already_handled=
+      for n in $names_already_handled; do
+        if test "$n" = "$name"; then
+          already_handled=yes
+          break
+        fi
+      done
+      if test -z "$already_handled"; then
+        names_already_handled="$names_already_handled $name"
+                        uppername=`echo "$name" | sed -e 'y|abcdefghijklmnopqrstuvwxyz./-|ABCDEFGHIJKLMNOPQRSTUVWXYZ___|'`
+        eval value=\"\$HAVE_LIB$uppername\"
+        if test -n "$value"; then
+          if test "$value" = yes; then
+            eval value=\"\$LIB$uppername\"
+            test -z "$value" || LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$value"
+            eval value=\"\$LTLIB$uppername\"
+            test -z "$value" || LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }$value"
+          else
+                                    :
+          fi
+        else
+                              found_dir=
+          found_la=
+          found_so=
+          found_a=
+          if test $use_additional = yes; then
+            if test -n "$shlibext" && test -f "$additional_libdir/lib$name.$shlibext"; then
+              found_dir="$additional_libdir"
+              found_so="$additional_libdir/lib$name.$shlibext"
+              if test -f "$additional_libdir/lib$name.la"; then
+                found_la="$additional_libdir/lib$name.la"
+              fi
+            else
+              if test -f "$additional_libdir/lib$name.$libext"; then
+                found_dir="$additional_libdir"
+                found_a="$additional_libdir/lib$name.$libext"
+                if test -f "$additional_libdir/lib$name.la"; then
+                  found_la="$additional_libdir/lib$name.la"
+                fi
+              fi
+            fi
+          fi
+          if test "X$found_dir" = "X"; then
+            for x in $LDFLAGS $LTLIBMPFR; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+              case "$x" in
+                -L*)
+                  dir=`echo "X$x" | sed -e 's/^X-L//'`
+                  if test -n "$shlibext" && test -f "$dir/lib$name.$shlibext"; then
+                    found_dir="$dir"
+                    found_so="$dir/lib$name.$shlibext"
+                    if test -f "$dir/lib$name.la"; then
+                      found_la="$dir/lib$name.la"
+                    fi
+                  else
+                    if test -f "$dir/lib$name.$libext"; then
+                      found_dir="$dir"
+                      found_a="$dir/lib$name.$libext"
+                      if test -f "$dir/lib$name.la"; then
+                        found_la="$dir/lib$name.la"
+                      fi
+                    fi
+                  fi
+                  ;;
+              esac
+              if test "X$found_dir" != "X"; then
+                break
+              fi
+            done
+          fi
+          if test "X$found_dir" != "X"; then
+                        LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }-L$found_dir -l$name"
+            if test "X$found_so" != "X"; then
+                                                        if test "$enable_rpath" = no || test "X$found_dir" = "X/usr/lib"; then
+                                LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$found_so"
+              else
+                                                                                haveit=
+                for x in $ltrpathdirs; do
+                  if test "X$x" = "X$found_dir"; then
+                    haveit=yes
+                    break
+                  fi
+                done
+                if test -z "$haveit"; then
+                  ltrpathdirs="$ltrpathdirs $found_dir"
+                fi
+                                if test "$hardcode_direct" = yes; then
+                                                      LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$found_so"
+                else
+                  if test -n "$hardcode_libdir_flag_spec" && test "$hardcode_minus_L" = no; then
+                                                            LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$found_so"
+                                                            haveit=
+                    for x in $rpathdirs; do
+                      if test "X$x" = "X$found_dir"; then
+                        haveit=yes
+                        break
+                      fi
+                    done
+                    if test -z "$haveit"; then
+                      rpathdirs="$rpathdirs $found_dir"
+                    fi
+                  else
+                                                                                haveit=
+                    for x in $LDFLAGS $LIBMPFR; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+                      if test "X$x" = "X-L$found_dir"; then
+                        haveit=yes
+                        break
+                      fi
+                    done
+                    if test -z "$haveit"; then
+                      LIBMPFR="${LIBMPFR}${LIBMPFR:+ }-L$found_dir"
+                    fi
+                    if test "$hardcode_minus_L" != no; then
+                                                                                        LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$found_so"
+                    else
+                                                                                                                                                                                LIBMPFR="${LIBMPFR}${LIBMPFR:+ }-l$name"
+                    fi
+                  fi
+                fi
+              fi
+            else
+              if test "X$found_a" != "X"; then
+                                LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$found_a"
+              else
+                                                LIBMPFR="${LIBMPFR}${LIBMPFR:+ }-L$found_dir -l$name"
+              fi
+            fi
+                        additional_includedir=
+            case "$found_dir" in
+              */lib | */lib/)
+                basedir=`echo "X$found_dir" | sed -e 's,^X,,' -e 's,/lib/*$,,'`
+                additional_includedir="$basedir/include"
+                ;;
+            esac
+            if test "X$additional_includedir" != "X"; then
+                                                                                                                if test "X$additional_includedir" != "X/usr/include"; then
+                haveit=
+                if test "X$additional_includedir" = "X/usr/local/include"; then
+                  if test -n "$GCC"; then
+                    case $host_os in
+                      linux*) haveit=yes;;
+                    esac
+                  fi
+                fi
+                if test -z "$haveit"; then
+                  for x in $CPPFLAGS $INCMPFR; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+                    if test "X$x" = "X-I$additional_includedir"; then
+                      haveit=yes
+                      break
+                    fi
+                  done
+                  if test -z "$haveit"; then
+                    if test -d "$additional_includedir"; then
+                                            INCMPFR="${INCMPFR}${INCMPFR:+ }-I$additional_includedir"
+                    fi
+                  fi
+                fi
+              fi
+            fi
+                        if test -n "$found_la"; then
+                                                        save_libdir="$libdir"
+              case "$found_la" in
+                */* | *\\*) . "$found_la" ;;
+                *) . "./$found_la" ;;
+              esac
+              libdir="$save_libdir"
+                            for dep in $dependency_libs; do
+                case "$dep" in
+                  -L*)
+                    additional_libdir=`echo "X$dep" | sed -e 's/^X-L//'`
+                                                                                                                                                                if test "X$additional_libdir" != "X/usr/lib"; then
+                      haveit=
+                      if test "X$additional_libdir" = "X/usr/local/lib"; then
+                        if test -n "$GCC"; then
+                          case $host_os in
+                            linux*) haveit=yes;;
+                          esac
+                        fi
+                      fi
+                      if test -z "$haveit"; then
+                        haveit=
+                        for x in $LDFLAGS $LIBMPFR; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+                          if test "X$x" = "X-L$additional_libdir"; then
+                            haveit=yes
+                            break
+                          fi
+                        done
+                        if test -z "$haveit"; then
+                          if test -d "$additional_libdir"; then
+                                                        LIBMPFR="${LIBMPFR}${LIBMPFR:+ }-L$additional_libdir"
+                          fi
+                        fi
+                        haveit=
+                        for x in $LDFLAGS $LTLIBMPFR; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+                          if test "X$x" = "X-L$additional_libdir"; then
+                            haveit=yes
+                            break
+                          fi
+                        done
+                        if test -z "$haveit"; then
+                          if test -d "$additional_libdir"; then
+                                                        LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }-L$additional_libdir"
+                          fi
+                        fi
+                      fi
+                    fi
+                    ;;
+                  -R*)
+                    dir=`echo "X$dep" | sed -e 's/^X-R//'`
+                    if test "$enable_rpath" != no; then
+                                                                  haveit=
+                      for x in $rpathdirs; do
+                        if test "X$x" = "X$dir"; then
+                          haveit=yes
+                          break
+                        fi
+                      done
+                      if test -z "$haveit"; then
+                        rpathdirs="$rpathdirs $dir"
+                      fi
+                                                                  haveit=
+                      for x in $ltrpathdirs; do
+                        if test "X$x" = "X$dir"; then
+                          haveit=yes
+                          break
+                        fi
+                      done
+                      if test -z "$haveit"; then
+                        ltrpathdirs="$ltrpathdirs $dir"
+                      fi
+                    fi
+                    ;;
+                  -l*)
+                                        names_next_round="$names_next_round "`echo "X$dep" | sed -e 's/^X-l//'`
+                    ;;
+                  *.la)
+                                                                                names_next_round="$names_next_round "`echo "X$dep" | sed -e 's,^X.*/,,' -e 's,^lib,,' -e 's,\.la$,,'`
+                    ;;
+                  *)
+                                        LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$dep"
+                    LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }$dep"
+                    ;;
+                esac
+              done
+            fi
+          else
+                                                            LIBMPFR="${LIBMPFR}${LIBMPFR:+ }-l$name"
+            LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }-l$name"
+          fi
+        fi
+      fi
+    done
+  done
+  if test "X$rpathdirs" != "X"; then
+    if test -n "$hardcode_libdir_separator"; then
+                        alldirs=
+      for found_dir in $rpathdirs; do
+        alldirs="${alldirs}${alldirs:+$hardcode_libdir_separator}$found_dir"
+      done
+            acl_save_libdir="$libdir"
+      libdir="$alldirs"
+      eval flag=\"$hardcode_libdir_flag_spec\"
+      libdir="$acl_save_libdir"
+      LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$flag"
+    else
+            for found_dir in $rpathdirs; do
+        acl_save_libdir="$libdir"
+        libdir="$found_dir"
+        eval flag=\"$hardcode_libdir_flag_spec\"
+        libdir="$acl_save_libdir"
+        LIBMPFR="${LIBMPFR}${LIBMPFR:+ }$flag"
+      done
+    fi
+  fi
+  if test "X$ltrpathdirs" != "X"; then
+            for found_dir in $ltrpathdirs; do
+      LTLIBMPFR="${LTLIBMPFR}${LTLIBMPFR:+ }-R$found_dir"
+    done
+  fi
+
+
+        ac_save_CPPFLAGS="$CPPFLAGS"
+
+  for element in $INCMPFR; do
+    haveit=
+    for x in $CPPFLAGS; do
+
+  acl_save_prefix="$prefix"
+  prefix="$acl_final_prefix"
+  acl_save_exec_prefix="$exec_prefix"
+  exec_prefix="$acl_final_exec_prefix"
+  eval x=\"$x\"
+  exec_prefix="$acl_save_exec_prefix"
+  prefix="$acl_save_prefix"
+
+      if test "X$x" = "X$element"; then
+        haveit=yes
+        break
+      fi
+    done
+    if test -z "$haveit"; then
+      CPPFLAGS="${CPPFLAGS}${CPPFLAGS:+ }$element"
+    fi
+  done
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for libmpfr" >&5
+$as_echo_n "checking for libmpfr... " >&6; }
+if test "${ac_cv_libmpfr+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+
+    ac_save_LIBS="$LIBS"
+    LIBS="$LIBS $LIBMPFR"
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <mpfr.h>
+int
+main ()
+{
+mpfr_exp_t exp; mpfr_t x;
+			 mpfr_frexp (&exp, x, x, MPFR_RNDN);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_libmpfr=yes
+else
+  ac_cv_libmpfr=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+    LIBS="$ac_save_LIBS"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_libmpfr" >&5
+$as_echo "$ac_cv_libmpfr" >&6; }
+  if test "$ac_cv_libmpfr" = yes; then
+    HAVE_LIBMPFR=yes
+
+$as_echo "#define HAVE_LIBMPFR 1" >>confdefs.h
+
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking how to link with libmpfr" >&5
+$as_echo_n "checking how to link with libmpfr... " >&6; }
+    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $LIBMPFR" >&5
+$as_echo "$LIBMPFR" >&6; }
+  else
+    HAVE_LIBMPFR=no
+            CPPFLAGS="$ac_save_CPPFLAGS"
+    LIBMPFR=
+    LTLIBMPFR=
+  fi
+
+
+
+
+
+
+  if test "$HAVE_LIBMPFR" != yes; then
+    if test "$with_mpfr" = yes; then
+      as_fn_error "MPFR is missing or unusable" "$LINENO" 5
+    else
+      { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: MPFR is missing or unusable; some features may be unavailable." >&5
+$as_echo "$as_me: WARNING: MPFR is missing or unusable; some features may be unavailable." >&2;}
+    fi
+  fi
+fi
+
 # --------------------- #
 # Check for libpython.  #
 # --------------------- #