nvptx: Support global constructors/destructors via 'collect2'

From ba5f6471d39e684fb740523651138a90a1b63cf9 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Sun, 13 Nov 2022 14:19:30 +0100
Subject: [PATCH] nvptx: Support global constructors/destructors via 'collect2'

The function attributes 'constructor', 'destructor', and 'init_priority' now
work, as do the C++ features making use of this.  Test cases with effective
target 'global_constructor' and 'init_priority' now generally work, and
'check-gcc-c++' test results greatly improve; no more "sorry, unimplemented:
global constructors not supported on this target".

This depends on <https://github.com/MentorEmbedded/nvptx-tools/pull/40> "'nm'"
generally, and for global destructors support: newlib
<https://inbox.sourceware.org/newlib/878rjqaku5.fsf@dem-tschwing-1.ger.mentorg.com/>
"nvptx: Implement '_exit' instead of 'exit'".

	gcc/
	* collect2.cc (write_c_file_glob): Allow for
	'COLLECT2_MAIN_REFERENCE' override.
	* config.gcc <case ${target} in nvptx-*>: Set 'use_collect2=yes'.
	* config/nvptx/nvptx.h: Adjust.
	gcc/testsuite/
	* gcc.dg/no_profile_instrument_function-attr-1.c: GCC/nvptx is
	'NO_DOT_IN_LABEL' but not 'NO_DOLLAR_IN_LABEL', so '$' may apper
	in identifiers.
	* lib/target-supports.exp
	(check_effective_target_global_constructor): Enable for nvptx.
	libgcc/
	* config.host <case ${host} in nvptx-*>: Add 'crtbegin.o',
	'crtend.o' to 'extra_parts'.
	* config/nvptx/crt0.c: Invoke '__do_global_ctors',
	'__do_global_dtors'.
	* config/nvptx/crtstuff.c: New.
	* config/nvptx/t-nvptx: Adjust.
---
 gcc/collect2.cc                               |  4 ++
 gcc/config.gcc                                |  1 +
 gcc/config/nvptx/nvptx.h                      | 35 ++++++++++-
 .../no_profile_instrument_function-attr-1.c   |  2 +-
 gcc/testsuite/lib/target-supports.exp         |  3 +-
 libgcc/config.host                            |  2 +-
 libgcc/config/nvptx/crt0.c                    |  5 ++
 libgcc/config/nvptx/crtstuff.c                | 58 +++++++++++++++++++
 libgcc/config/nvptx/t-nvptx                   | 15 ++++-
 9 files changed, 118 insertions(+), 7 deletions(-)
 create mode 100644 libgcc/config/nvptx/crtstuff.c

diff --git a/gcc/collect2.cc b/gcc/collect2.cc
index d81c7f28f16..945a9ff86dd 100644
--- a/gcc/collect2.cc
+++ b/gcc/collect2.cc
@@ -2238,8 +2238,12 @@  write_c_file_glob (FILE *stream, const char *name ATTRIBUTE_UNUSED)
     fprintf (stream, "\tdereg_frame,\n");
   fprintf (stream, "\t0\n};\n\n");
 
+# ifdef COLLECT2_MAIN_REFERENCE
+  fprintf (stream, "%s\n\n", COLLECT2_MAIN_REFERENCE);
+# else
   fprintf (stream, "extern entry_pt %s;\n", NAME__MAIN);
   fprintf (stream, "entry_pt *__main_reference = %s;\n\n", NAME__MAIN);
+# endif
 }
 #endif /* ! LD_INIT_SWITCH */
 
diff --git a/gcc/config.gcc b/gcc/config.gcc
index b5eda046033..9b27efd5f51 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -2783,6 +2783,7 @@  nvptx-*)
 	tm_file="${tm_file} newlib-stdint.h"
 	use_gcc_stdint=wrap
 	tmake_file="nvptx/t-nvptx"
+	use_collect2=yes
 	if test x$enable_as_accelerator = xyes; then
 		extra_programs="${extra_programs} mkoffload\$(exeext)"
 		tm_file="${tm_file} nvptx/offload.h"
diff --git a/gcc/config/nvptx/nvptx.h b/gcc/config/nvptx/nvptx.h
index b1cbe5d417b..bc1021a8031 100644
--- a/gcc/config/nvptx/nvptx.h
+++ b/gcc/config/nvptx/nvptx.h
@@ -35,7 +35,39 @@ 
    '../../gcc.cc:asm_options', 'HAVE_GNU_AS'.  */
 #define ASM_SPEC "%{v}"
 
-#define STARTFILE_SPEC "%{mmainkernel:crt0.o%s}"
+#define STARTFILE_SPEC \
+  STARTFILE_SPEC_MMAINKERNEL \
+  " " STARTFILE_SPEC_CDTOR
+
+#define ENDFILE_SPEC \
+  ENDFILE_SPEC_CDTOR
+
+#define STARTFILE_SPEC_MMAINKERNEL "%{mmainkernel:crt0.o%s}"
+
+/* Support for global constructors/destructors is implemented via
+   'collect2' and the following helpers.  */
+
+#define STARTFILE_SPEC_CDTOR "crtbegin.o%s"
+
+#define ENDFILE_SPEC_CDTOR "crtend.o%s"
+
+/* nvptx does its own wrapping of 'main'
+   (see 'libgcc/config/nvptx/crt0.c:__main').  */
+#define HAS_INIT_SECTION
+
+/* For example with old Nvidia Tesla K20c, Driver Version: 361.93.02, the
+   function pointers stored in the '__CTOR_LIST__', '__DTOR_LIST__' arrays
+   evidently evaluate to NULL in JIT compilation.  Avoiding the use of
+   assembler names ('write_list_with_asm') doesn't help, but defining a dummy
+   function next to the arrays apparently does work around this issue...
+
+   The default '__main_reference' synthesized by 'collect2' refers to our
+   'crt0.o' '__main' function with incompatible signature:
+
+       error   : Function '__main' not declared __global__ in all source files
+
+   Address both these issues via 'COLLECT2_MAIN_REFERENCE'.  */
+#define COLLECT2_MAIN_REFERENCE "__attribute__((unused)) static void dummy () {}"
 
 #define TARGET_CPU_CPP_BUILTINS() nvptx_cpu_cpp_builtins ()
 
@@ -354,7 +386,6 @@  struct GTY(()) machine_function
 #define MOVE_MAX 8
 #define MOVE_RATIO(SPEED) 4
 #define FUNCTION_MODE QImode
-#define HAS_INIT_SECTION 1
 
 /* The C++ front end insists to link against libstdc++ -- which we don't build.
    Tell it to instead link against the innocuous libgcc.  */
diff --git a/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c b/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c
index 909f8a68479..5b4101cf596 100644
--- a/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c
+++ b/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c
@@ -18,7 +18,7 @@  int main ()
   return foo ();
 }
 
-/* { dg-final { scan-tree-dump-times "__gcov0\[._\]main.* = PROF_edge_counter" 1 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "__gcov0\[$._\]main.* = PROF_edge_counter" 1 "optimized"} } */
 /* { dg-final { scan-tree-dump-times "__gcov_indirect_call_profiler_v" 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times "__gcov_time_profiler_counter = " 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times "__gcov_init" 1 "optimized" } } */
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index d2de761adb5..ba9b045ebd4 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -907,8 +907,7 @@  proc check_effective_target_nonlocal_goto {} {
 # Return 1 if global constructors are supported, 0 otherwise.
 
 proc check_effective_target_global_constructor {} {
-    if { [istarget nvptx-*-*]
-	 || [istarget bpf-*-*] } {
+    if { [istarget bpf-*-*] } {
 	return 0
     }
     return 1
diff --git a/libgcc/config.host b/libgcc/config.host
index eb23abe89f5..25072f41860 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -1499,7 +1499,7 @@  m32c-*-elf*)
  	;;
 nvptx-*)
 	tmake_file="$tmake_file nvptx/t-nvptx"
-	extra_parts="crt0.o"
+	extra_parts="crt0.o crtbegin.o crtend.o"
 	;;
 *)
 	echo "*** Configuration ${host} not supported" 1>&2
diff --git a/libgcc/config/nvptx/crt0.c b/libgcc/config/nvptx/crt0.c
index abf047327ae..6a49790f479 100644
--- a/libgcc/config/nvptx/crt0.c
+++ b/libgcc/config/nvptx/crt0.c
@@ -19,6 +19,8 @@ 
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include "gbl-ctors.h"
+
 int *__exitval_ptr;
 
 extern void __attribute__((noreturn)) exit (int status);
@@ -47,5 +49,8 @@  __main (int *rval_ptr, int argc, void **argv)
   __nvptx_stacks[0] = stack + sizeof stack;
   __nvptx_uni[0] = 0;
 
+  __do_global_ctors ();
+  atexit (__do_global_dtors);
+
   exit (main (argc, argv));
 }
diff --git a/libgcc/config/nvptx/crtstuff.c b/libgcc/config/nvptx/crtstuff.c
new file mode 100644
index 00000000000..0823fc49901
--- /dev/null
+++ b/libgcc/config/nvptx/crtstuff.c
@@ -0,0 +1,58 @@ 
+/* Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3, or (at your option) any
+   later version.
+
+   This file is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "gbl-ctors.h"
+
+/* The common 'crtstuff.c' doesn't quite provide what we need, so we roll our
+   own.
+
+   There's no technical reason in this configuration here to split the two
+   functions '__do_global_ctors' and '__do_global_ctors' into two separate
+   files (via 'CRT_BEGIN' and 'CRT_END'): 'crtbegin.o' and 'crtend.o', but we
+   do so anyway, for symmetry with other configurations.  */
+
+#ifdef CRT_BEGIN
+
+void
+__do_global_ctors (void)
+{
+  DO_GLOBAL_CTORS_BODY;
+}
+
+#elif defined(CRT_END) /* ! CRT_BEGIN */
+
+void
+__do_global_dtors (void)
+{
+  /* In this configuration here, there's no way that "this routine is run more
+     than once [...] when exit is called recursively": for nvptx target, the
+     call to '__do_global_dtors' is registered via 'atexit', which doesn't
+     re-enter a function already run.
+     Therefore, we do *not* "arrange to remember where in the list we left off
+     processing".  */
+  func_ptr *p;
+  for (p = __DTOR_LIST__ + 1; *p; )
+    (*p++) ();
+}
+
+#else /* ! CRT_BEGIN && ! CRT_END */
+#error "One of CRT_BEGIN or CRT_END must be defined."
+#endif
diff --git a/libgcc/config/nvptx/t-nvptx b/libgcc/config/nvptx/t-nvptx
index ede0bf0f87d..9a0454c3a4d 100644
--- a/libgcc/config/nvptx/t-nvptx
+++ b/libgcc/config/nvptx/t-nvptx
@@ -3,7 +3,7 @@  LIB2ADD=$(srcdir)/config/nvptx/reduction.c \
 	$(srcdir)/config/nvptx/atomic.c
 
 LIB2ADDEH=
-LIB2FUNCS_EXCLUDE=__main
+LIB2FUNCS_EXCLUDE=
 
 crt0.o: $(srcdir)/config/nvptx/crt0.c
 	$(crt_compile) -c $<
@@ -12,3 +12,16 @@  crt0.o: $(srcdir)/config/nvptx/crt0.c
 # support it, and it may cause the build to fail, because of alloca usage, for
 # example.
 INHIBIT_LIBC_CFLAGS = -Dinhibit_libc
+
+# Support for global constructors/destructors is implemented via
+# 'collect2' and the following helpers.
+
+LIB2FUNCS_EXCLUDE += __main
+
+CUSTOM_CRTSTUFF = yes
+
+crtbegin.o: $(srcdir)/config/nvptx/crtstuff.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_BEGIN
+
+crtend.o: $(srcdir)/config/nvptx/crtstuff.c
+	$(crt_compile) $(CRTSTUFF_T_CFLAGS) -c $< -DCRT_END
-- 
2.25.1