From 573a66e4146c9a65d895af9081a4d3d49cfc9e7a Mon Sep 17 00:00:00 2001
From: Drew DeVault <sir@cmpwn.com>
Date: Wed, 9 Dec 2020 16:07:26 +0000
Subject: [PATCH] configure: Add --enable-autolink-libatomic, use in
 LINK_GCC_C_SEQUENCE_SPEC [PR81358]

This fixes issues with RISC-V.
---
 Makefile.in           |  1 +
 gcc/config.in         |  6 ++++++
 gcc/config/gnu-user.h | 12 +++++++++++-
 gcc/configure         | 32 ++++++++++++++++++++++++++++++--
 gcc/configure.ac      | 22 +++++++++++++++++++++-
 gcc/doc/install.texi  |  8 ++++++++
 gcc/doc/tm.texi       |  8 +++++++-
 gcc/doc/tm.texi.in    |  8 +++++++-
 gcc/gcc.cc            | 12 +++++++++++-
 9 files changed, 102 insertions(+), 7 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index b564ddbf792..a95c7407d16 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -232,6 +232,7 @@ HOST_EXPORTS = \
 	RANLIB_FOR_TARGET="$(RANLIB_FOR_TARGET)"; export RANLIB_FOR_TARGET; \
 	READELF_FOR_TARGET="$(READELF_FOR_TARGET)"; export READELF_FOR_TARGET; \
 	TOPLEVEL_CONFIGURE_ARGUMENTS="$(TOPLEVEL_CONFIGURE_ARGUMENTS)"; export TOPLEVEL_CONFIGURE_ARGUMENTS; \
+	TARGET_CONFIGDIRS="$(TARGET_CONFIGDIRS)"; export TARGET_CONFIGDIRS; \
 	HOST_LIBS="$(STAGE1_LIBS)"; export HOST_LIBS; \
 	GMPLIBS="$(HOST_GMPLIBS)"; export GMPLIBS; \
 	GMPINC="$(HOST_GMPINC)"; export GMPINC; \
diff --git a/gcc/config.in b/gcc/config.in
index f0fbf123aa8..af84efc4f9e 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -118,6 +118,12 @@
 #endif
 
 
+/* Define if libatomic should always be linked. */
+#ifndef USED_FOR_TARGET
+#undef ENABLE_AUTOLINK_LIBATOMIC
+#endif
+
+
 /* Define to 1 to specify that we are using the BID decimal floating point
    format instead of DPD */
 #ifndef USED_FOR_TARGET
diff --git a/gcc/config/gnu-user.h b/gcc/config/gnu-user.h
index 8433e56c3e1..0347f10da8b 100644
--- a/gcc/config/gnu-user.h
+++ b/gcc/config/gnu-user.h
@@ -109,8 +109,18 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define LINK_EH_SPEC "%{!static|static-pie:--eh-frame-hdr} "
 #endif
 
+#if !defined(LINK_LIBATOMIC_SPEC) && defined(ENABLE_AUTOLINK_LIBATOMIC)
+#  ifdef LD_AS_NEEDED_OPTION
+#    define LINK_LIBATOMIC_SPEC LD_AS_NEEDED_OPTION " -latomic " LD_NO_AS_NEEDED_OPTION
+#  else
+#    define LINK_LIBATOMIC_SPEC "-latomic"
+#  endif
+#elif !defined(LINK_LIBATOMIC_SPEC)
+#  define LINK_LIBATOMIC_SPEC ""
+#endif
+
 #define GNU_USER_TARGET_LINK_GCC_C_SEQUENCE_SPEC \
-  "%{static|static-pie:--start-group} %G %{!nolibc:%L} \
+  "%{static|static-pie:--start-group} %G %{!nolibc:" LINK_LIBATOMIC_SPEC " %L} \
    %{static|static-pie:--end-group}%{!static:%{!static-pie:%G}}"
 
 #undef LINK_GCC_C_SEQUENCE_SPEC
diff --git a/gcc/configure b/gcc/configure
index 2f6b3265a6c..6dc65bf4ccb 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -981,6 +981,7 @@ with_changes_root_url
 enable_languages
 with_multilib_list
 with_multilib_generator
+enable_autolink_libatomic
 with_zstd
 with_zstd_include
 with_zstd_lib
@@ -1710,6 +1711,9 @@ Optional Features:
   --disable-shared        don't provide a shared libgcc
   --disable-gcov          don't provide libgcov and related host tools
   --enable-languages=LIST specify which front-ends to build
+  --enable-autolink-libatomic
+                          enable automatic linking of libatomic (ignored if
+                          not built)
   --disable-rpath         do not hardcode runtime library paths
   --enable-sjlj-exceptions
                           arrange to use setjmp/longjmp exception handling
@@ -8324,7 +8328,6 @@ else
 fi
 
 
-
 # Check whether --with-multilib-generator was given.
 if test "${with_multilib_generator+set}" = set; then :
   withval=$with_multilib_generator; :
@@ -8332,6 +8335,32 @@ else
   with_multilib_generator=default
 fi
 
+# If libatomic is available, whether it should be linked automatically
+# Check whether --enable-autolink-libatomic was given.
+if test "${enable_autolink_libatomic+set}" = set; then :
+  enableval=$enable_autolink_libatomic;
+  case $enable_autolink_libatomic in
+    yes | no) ;;
+    *) as_fn_error $? "'$enable_autolink_libatomic' is an invalid value for
+--enable-autolink-libatomic.  Valid choices are 'yes' and 'no'." "$LINENO" 5 ;;
+  esac
+
+else
+  enable_autolink_libatomic=''
+fi
+
+
+if test x$enable_autolink_libatomic = xyes; then
+  if echo " ${TARGET_CONFIGDIRS} " | grep " libatomic " > /dev/null 2>&1 ; then
+
+$as_echo "#define ENABLE_AUTOLINK_LIBATOMIC 1" >>confdefs.h
+
+  else
+    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: libatomic is not build for this target, --enable-autolink-libatomic ignored" >&5
+$as_echo "$as_me: WARNING: libatomic is not build for this target, --enable-autolink-libatomic ignored" >&2;}
+  fi
+fi
+
 
 # -------------------------
 # Checks for other programs
@@ -34296,4 +34325,3 @@ if test -n "$ac_unrecognized_opts" && test "$enable_option_checking" != no; then
 $as_echo "$as_me: WARNING: unrecognized options: $ac_unrecognized_opts" >&2;}
 fi
 
-
diff --git a/gcc/configure.ac b/gcc/configure.ac
index e683d3a7a5f..07c81c78336 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -1205,6 +1205,27 @@ AC_ARG_WITH(multilib-generator,
 :,
 with_multilib_generator=default)
 
+# If libatomic is available, whether it should be linked automatically
+AC_ARG_ENABLE(autolink-libatomic,
+[AS_HELP_STRING([--enable-autolink-libatomic],
+		[enable automatic linking of libatomic (ignored if not built)])],
+[
+  case $enable_autolink_libatomic in
+    yes | no) ;;
+    *) AC_MSG_ERROR(['$enable_autolink_libatomic' is an invalid value for
+--enable-autolink-libatomic.  Valid choices are 'yes' and 'no'.]) ;;
+  esac
+], [enable_autolink_libatomic=''])
+
+if test x$enable_autolink_libatomic = xyes; then
+  if echo " ${TARGET_CONFIGDIRS} " | grep " libatomic " > /dev/null 2>&1 ; then
+    AC_DEFINE(ENABLE_AUTOLINK_LIBATOMIC, 1,
+	[Define if libatomic should always be linked.])
+  else
+    AC_MSG_WARN([libatomic is not build for this target, --enable-autolink-libatomic ignored])
+  fi
+fi
+
 # -------------------------
 # Checks for other programs
 # -------------------------
@@ -7839,4 +7860,3 @@ done
 ], 
 [subdirs='$subdirs'])
 AC_OUTPUT
-
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 48408d842db..c90be0ee750 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -2295,6 +2295,14 @@ files, but these changed header paths may conflict with some compilation
 environments.  Enabled by default, and may be disabled using
 @option{--disable-canonical-system-headers}.
 
+@item --enable-autolink-libatomic
+@itemx --disable-autolink-libatomic
+Tell GCC that it should automatically link libatomic; if supported by
+the linker, the file is only linked as needed. This flag is ignored
+when libatomic is not built. Note that this conigure flag is in particular
+useful when building an offloading-target compiler; as for those, a
+user had to specify @code{-foffload=target=-latomic} otherwise.
+
 @item --with-glibc-version=@var{major}.@var{minor}
 Tell GCC that when the GNU C Library (glibc) is used on the target it
 will be version @var{major}.@var{minor} or later.  Normally this can
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index c5006afc00d..56b62c69ae8 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -381,7 +381,13 @@ the argument @option{-lgcc} to tell the linker to do the search.
 
 @defmac LINK_GCC_C_SEQUENCE_SPEC
 The sequence in which libgcc and libc are specified to the linker.
-By default this is @code{%G %L %G}.
+By default this is @code{%G LINK_LIBATOMIC_SPEC %L %G}.
+@end defmac
+
+@defmac LINK_LIBATOMIC_SPEC
+This macro is used in the default @code{LINK_GCC_C_SEQUENCE_SPEC} to link
+libatomic. By default, it is unset unless @code{ENABLE_AUTOLINK_LIBATOMIC}
+is set.
 @end defmac
 
 @defmac POST_LINK_SPEC
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index f869ddd5e5b..57c93f24ac3 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -381,7 +381,13 @@ the argument @option{-lgcc} to tell the linker to do the search.
 
 @defmac LINK_GCC_C_SEQUENCE_SPEC
 The sequence in which libgcc and libc are specified to the linker.
-By default this is @code{%G %L %G}.
+By default this is @code{%G LINK_LIBATOMIC_SPEC %L %G}.
+@end defmac
+
+@defmac LINK_LIBATOMIC_SPEC
+This macro is used in the default @code{LINK_GCC_C_SEQUENCE_SPEC} to link
+libatomic. By default, it is unset unless @code{ENABLE_AUTOLINK_LIBATOMIC}
+is set.
 @end defmac
 
 @defmac POST_LINK_SPEC
diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index 735b2b1bba1..f10f3c91aa7 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -987,13 +987,23 @@ proper position among the other output files.  */
 # define ASM_DEBUG_OPTION_SPEC ""
 #endif
 
+#if !defined(LINK_LIBATOMIC_SPEC) && defined(ENABLE_AUTOLINK_LIBATOMIC)
+#  ifdef LD_AS_NEEDED_OPTION
+#    define LINK_LIBATOMIC_SPEC LD_AS_NEEDED_OPTION " -latomic " LD_NO_AS_NEEDED_OPTION
+#  else
+#    define LINK_LIBATOMIC_SPEC "-latomic"
+#  endif
+#elif !defined(LINK_LIBATOMIC_SPEC)
+#  define LINK_LIBATOMIC_SPEC ""
+#endif
+
 /* Here is the spec for running the linker, after compiling all files.  */
 
 /* This is overridable by the target in case they need to specify the
    -lgcc and -lc order specially, yet not require them to override all
    of LINK_COMMAND_SPEC.  */
 #ifndef LINK_GCC_C_SEQUENCE_SPEC
-#define LINK_GCC_C_SEQUENCE_SPEC "%G %{!nolibc:%L %G}"
+#define LINK_GCC_C_SEQUENCE_SPEC "%G %{!nolibc:" LINK_LIBATOMIC_SPEC " %L %G}"
 #endif
 
 #ifdef ENABLE_DEFAULT_SSP
