Skip libstdc++ debug build in early bootstrap stages

As mentioned in PR 90770, this is a patch that Debian have been carrying
for some time. The additional unoptimized copies of libstdc++ libs that
get built during each stage are never going to be used, so don't bother
building them.

For a profiled bootstrap this means we won't train the compiler on the
unoptimized library code with assertions enabled, but that doesn't seem
like a big problem, as the same code has already been compiled once for
the main libstdc++ library.

	* acinclude.m4 (GLIBCXX_ENABLE_DEBUG): Only do debug build for final
	stage of bootstrap.
	* configure: Regenerate.

From-SVN: r272509

3 files changed, 31 insertions, 3 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d5e4c85..ac98c0d 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,9 @@
 2019-06-20  Jonathan Wakely  <jwakely@redhat.com>
 
+	* acinclude.m4 (GLIBCXX_ENABLE_DEBUG): Only do debug build for final
+	stage of bootstrap.
+	* configure: Regenerate.
+
 	* include/std/variant (_Variant_storage, _Extra_visit_slot_needed):
 	Qualify calls to __never_valueless.
 
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 19e9f14..fad390b 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -2899,8 +2899,20 @@ dnl       Where DEFAULT is either `yes' or `no'.
 dnl
 AC_DEFUN([GLIBCXX_ENABLE_DEBUG], [
   AC_MSG_CHECKING([for additional debug build])
+  skip_debug_build=
   GLIBCXX_ENABLE(libstdcxx-debug,$1,,[build extra debug library])
-  AC_MSG_RESULT($enable_libstdcxx_debug)
+  if test x$enable_libstdcxx_debug = xyes; then
+    if test -f $toplevel_builddir/../stage_final \
+      && test -f $toplevel_builddir/../stage_current; then
+      stage_final=`cat $toplevel_builddir/../stage_final`
+      stage_current=`cat $toplevel_builddir/../stage_current`
+      if test x$stage_current != x$stage_final ; then
+	skip_debug_build=" (skipped for bootstrap stage $stage_current)"
+	enable_libstdcxx_debug=no
+      fi
+    fi
+  fi
+  AC_MSG_RESULT($enable_libstdcxx_debug$skip_debug_build)
   GLIBCXX_CONDITIONAL(GLIBCXX_BUILD_DEBUG, test $enable_libstdcxx_debug = yes)
 ])
 
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 4788acb..62d9cb4 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -18257,6 +18257,7 @@ $as_echo "$as_me: Debug build flags set to $DEBUG_FLAGS" >&6;}
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for additional debug build" >&5
 $as_echo_n "checking for additional debug build... " >&6; }
+  skip_debug_build=
    # Check whether --enable-libstdcxx-debug was given.
 if test "${enable_libstdcxx_debug+set}" = set; then :
   enableval=$enable_libstdcxx_debug;
@@ -18270,8 +18271,19 @@ else
 fi
 
 
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_libstdcxx_debug" >&5
-$as_echo "$enable_libstdcxx_debug" >&6; }
+  if test x$enable_libstdcxx_debug = xyes; then
+    if test -f $toplevel_builddir/../stage_final \
+      && test -f $toplevel_builddir/../stage_current; then
+      stage_final=`cat $toplevel_builddir/../stage_final`
+      stage_current=`cat $toplevel_builddir/../stage_current`
+      if test x$stage_current != x$stage_final ; then
+	skip_debug_build=" (skipped for bootstrap stage $stage_current)"
+	enable_libstdcxx_debug=no
+      fi
+    fi
+  fi
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $enable_libstdcxx_debug$skip_debug_build" >&5
+$as_echo "$enable_libstdcxx_debug$skip_debug_build" >&6; }