libgo: test linking split-stack and non-split-stack together

    
    PPC has split-stack support in current GCC, but old version of gold will
    reject attempts to link PPC split-stack and non-split-stack code
    together.  Test for that, and don't compile the C code with
    -fsplit-stack if it doesn't work.
    
    Reviewed-on: https://go-review.googlesource.com/14594

From-SVN: r227802

gcc/go/gofrontend/MERGE

-23392287e9a26956977987fe95f337c5be4d6417
+6f0ac34e139755c319368757fe2a093f1e5bde49
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/configure

@@ -14007,7 +14007,32 @@ CFLAGS=$CFLAGS_hold
 fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $libgo_cv_c_split_stack_supported" >&5
 $as_echo "$libgo_cv_c_split_stack_supported" >&6; }
-if test "$libgo_cv_c_split_stack_supported" = yes; then
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether linker supports split/non-split linked together" >&5
+$as_echo_n "checking whether linker supports split/non-split linked together... " >&6; }
+if test "${libgo_cv_c_linker_split_non_split+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest1.c << EOF
+extern void f();
+int main() { f(); return 0; }
+EOF
+cat > conftest2.c << EOF
+void f() {}
+EOF
+$CC -c -fsplit-stack $CFLAGS $CPPFLAGS conftest1.c
+$CC -c $CFLAGS $CPPFLAGS conftest2.c
+if $CC -o conftest conftest1.$ac_objext conftest2.$ac_objext; then
+  libgo_cv_c_linker_split_non_split=yes
+else
+  libgo_cv_c_linker_split_non_split=no
+fi
+rm -f conftest1.* conftest2.* conftest
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libgo_cv_c_linker_split_non_split" >&5
+$as_echo "$libgo_cv_c_linker_split_non_split" >&6; }
+
+if test "$libgo_cv_c_split_stack_supported" = yes -a "$libgo_cv_c_linker_split_non_split" = yes; then
   SPLIT_STACK=-fsplit-stack
 
 $as_echo "#define USING_SPLIT_STACK 1" >>confdefs.h
@@ -14016,7 +14041,7 @@ else
   SPLIT_STACK=
 fi
 
- if test "$libgo_cv_c_split_stack_supported" = yes; then
+ if test "$libgo_cv_c_split_stack_supported" = yes -a "$libgo_cv_c_linker_split_non_split" = yes; then
   USING_SPLIT_STACK_TRUE=
   USING_SPLIT_STACK_FALSE='#'
 else

libgo/configure.ac

@@ -374,7 +374,29 @@ AC_COMPILE_IFELSE([[int i;]],
 [libgo_cv_c_split_stack_supported=yes],
 [libgo_cv_c_split_stack_supported=no])
 CFLAGS=$CFLAGS_hold])
-if test "$libgo_cv_c_split_stack_supported" = yes; then
+
+dnl Make sure the linker permits -fsplit-stack.  Old versions of gold will
+dnl reject split-stack code calling non-split-stack code on targets
+dnl they don't support.
+AC_CACHE_CHECK([whether linker supports split/non-split linked together],
+[libgo_cv_c_linker_split_non_split],
+[cat > conftest1.c << EOF
+extern void f();
+int main() { f(); return 0; }
+EOF
+cat > conftest2.c << EOF
+void f() {}
+EOF
+$CC -c -fsplit-stack $CFLAGS $CPPFLAGS conftest1.c
+$CC -c $CFLAGS $CPPFLAGS conftest2.c
+if $CC -o conftest conftest1.$ac_objext conftest2.$ac_objext; then
+  libgo_cv_c_linker_split_non_split=yes
+else
+  libgo_cv_c_linker_split_non_split=no
+fi
+rm -f conftest1.* conftest2.* conftest])
+
+if test "$libgo_cv_c_split_stack_supported" = yes -a "$libgo_cv_c_linker_split_non_split" = yes; then
   SPLIT_STACK=-fsplit-stack
   AC_DEFINE(USING_SPLIT_STACK, 1,
 		[Define if the compiler supports -fsplit-stack])
@@ -383,13 +405,15 @@ else
 fi
 AC_SUBST(SPLIT_STACK)
 AM_CONDITIONAL(USING_SPLIT_STACK,
-	test "$libgo_cv_c_split_stack_supported" = yes)
+	test "$libgo_cv_c_split_stack_supported" = yes -a "$libgo_cv_c_linker_split_non_split" = yes)
 
 dnl Check whether the linker does stack munging when calling from
 dnl split-stack into non-split-stack code.  We check this by looking
 dnl at the --help output.  FIXME: This is only half right: it's
 dnl possible for the linker to support this for some targets but not
 dnl others.
+dnl This is slightly different from the above check, which is whether
+dnl the linker permits the call at all.
 AC_CACHE_CHECK([whether linker supports split stack],
 [libgo_cv_c_linker_supports_split_stack],
 [libgo_cv_c_linker_supports_split_stack=no