nvptx target: Global constructor, destructor support, via nvptx-tools 'ld'

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".

For proper execution test results, this depends on
<https://github.com/SourceryTools/nvptx-tools/commit/96f8fc59a757767b9e98157d95c21e9fef22a93b>
"ld: Global constructor/destructor support".

	gcc/
	* config/nvptx/nvptx.h: Configure global constructor, destructor
	support.
	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/nvptx/crt0.c (__gbl_ctors): New weak function.
	(__main): Invoke it.
	* config/nvptx/gbl-ctors.c: New.
	* config/nvptx/t-nvptx: Configure global constructor, destructor
	support.

3 files changed, 15 insertions, 4 deletions

diff --git a/gcc/config/nvptx/nvptx.h b/gcc/config/nvptx/nvptx.h
index e282aad..74f4a68 100644
--- a/gcc/config/nvptx/nvptx.h
+++ b/gcc/config/nvptx/nvptx.h
@@ -356,7 +356,19 @@ struct GTY(()) machine_function
 #define MOVE_MAX 8
 #define MOVE_RATIO(SPEED) 4
 #define FUNCTION_MODE QImode
-#define HAS_INIT_SECTION 1
+
+/* Implement global constructor, destructor support in a conceptually simpler
+   way than using 'collect2' (the program): implement the respective
+   functionality in the nvptx-tools 'ld'.  This however still requires the
+   compiler-side effects corresponding to 'USE_COLLECT2': the global
+   constructor, destructor support functions need to have external linkage, and
+   therefore names that are "unique across the whole link".  Use
+   '!targetm.have_ctors_dtors' to achieve this (..., and thus don't need to
+   provide 'targetm.asm_out.constructor', 'targetm.asm_out.destructor').  */
+#define TARGET_HAVE_CTORS_DTORS false
+
+/* See 'libgcc/config/nvptx/crt0.c' for wrapping of 'main'.  */
+#define HAS_INIT_SECTION
 
 /* 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 909f8a6..5b4101c 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 f0f6da5..a3992fa 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -942,8 +942,7 @@ 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