[c++] Don't emit exception tables for UI_NONE

If a target does not support exceptions, it can indicate this by returning
UI_NONE in TARGET_EXCEPT_UNWIND_INFO.  Currently the compiler still emits
exception tables for such a target.

This patch makes sure that no exception tables are emitted if the target does
not support exceptions.  This allows us to remove a workaround in
TARGET_ASM_BYTE_OP in the nvptx port.

Build on x86_64 with nvptx accelerator, and tested libgomp.

Build and reg-tested on x86_64.

2018-08-03  Tom de Vries  <tdevries@suse.de>

	* common/config/nvptx/nvptx-common.c (nvptx_except_unwind_info): Return
	UI_NONE.
	* config/nvptx/nvptx.c (TARGET_ASM_BYTE_OP): Remove define.
	* except.c (output_function_exception_table): Do early exit if
	targetm_common.except_unwind_info (&global_options) == UI_NONE.

From-SVN: r263287

gcc/ChangeLog

+2018-08-03  Tom de Vries  <tdevries@suse.de>
+
+	* common/config/nvptx/nvptx-common.c (nvptx_except_unwind_info): Return
+	UI_NONE.
+	* config/nvptx/nvptx.c (TARGET_ASM_BYTE_OP): Remove define.
+	* except.c (output_function_exception_table): Do early exit if
+	targetm_common.except_unwind_info (&global_options) == UI_NONE.
+
 2018-08-03  Martin Liska  <mliska@suse.cz>
 
 	* predict.c (dump_prediction): Change to 2 digits

gcc/common/config/nvptx/nvptx-common.c

@@ -33,7 +33,7 @@ along with GCC; see the file COPYING3.  If not see
 enum unwind_info_type
 nvptx_except_unwind_info (struct gcc_options *opts ATTRIBUTE_UNUSED)
 {
-  return UI_TARGET;
+  return UI_NONE;
 }
 
 #undef TARGET_HAVE_NAMED_SECTIONS

gcc/config/nvptx/nvptx.c

@@ -6051,9 +6051,6 @@ nvptx_can_change_mode_class (machine_mode, machine_mode, reg_class_t)
 #undef TARGET_HAVE_SPECULATION_SAFE_VALUE
 #define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed
 
-#undef TARGET_ASM_BYTE_OP
-#define TARGET_ASM_BYTE_OP "// .byte "
-
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-nvptx.h"

gcc/except.c

@@ -3189,7 +3189,8 @@ output_function_exception_table (int section)
   rtx personality = get_personality_function (current_function_decl);
 
   /* Not all functions need anything.  */
-  if (!crtl->uses_eh_lsda)
+  if (!crtl->uses_eh_lsda
+      || targetm_common.except_unwind_info (&global_options) == UI_NONE)
     return;
 
   /* No need to emit any boilerplate stuff for the cold part.  */