debug: Allow means for targets to opt out of CTF/BTF support

CTF/BTF debug formats can be safely enabled for all ELF-based targets by
default in GCC.

CTF/BTF debug formats now adopt a similar approach as taken for DWARF debug
format via the DWARF2_DEBUGGING_INFO.
  - By default, CTF/BTF formats can be enabled for all ELF-based targets.
  - By default, CTF/BTF formats can be disabled for all non ELF-based targets.
  - If the user passed a -gctf but CTF is not enabled for the target, GCC
  issues an error to the user (as is done currently with other debug formats) -
  "target system does not support the 'ctf' debug format". Analogous behavior
  for -gbtf command line option.

A previous commit disabled the CTF and BTF testcases on the AIX platform. This
is not necessary now that CTF and BTF debug formats are disabled by default on
all non-ELF targets. GCC emits an error message when -gctf/-gbtf is used on
such platforms and these tests will be skipped.

gcc/

	* config/elfos.h (CTF_DEBUGGING_INFO): New definition.
	(BTF_DEBUGGING_INFO): Likewise.
	* doc/tm.texi.in: Document the new macros.
	* doc/tm.texi: Regenerated.
	* toplev.c: Guard initialization of debug hooks.

gcc/testsuite/

	* gcc.dg/debug/btf/btf.exp: Do not run BTF testsuite if target does not
	support BTF format. Remove redundant check for AIX.
	* gcc.dg/debug/ctf/ctf.exp: Do not run CTF testsuite if target does not
	support CTF format. Remove redundant check for AIX.
	* lib/gcc-dg.exp: Remove redundant check for AIX.

1 files changed, 26 insertions, 0 deletions

diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 3ad3944..c8f4abe 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -9947,6 +9947,8 @@ This describes how to specify debugging information.
 * File Names and DBX:: Macros controlling output of file names in DBX format.
 * DWARF::              Macros for DWARF format.
 * VMS Debug::          Macros for VMS debug format.
+* CTF Debug::          Macros for CTF debug format.
+* BTF Debug::          Macros for BTF debug format.
 @end menu
 
 @node All Debuggers
@@ -10374,6 +10376,30 @@ behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and
 @code{TARGET_OPTION_OVERRIDE}.
 @end defmac
 
+@need 2000
+@node CTF Debug
+@subsection Macros for CTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for CTF debug format.
+
+@defmac CTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in CTF debug
+format in response to the @option{-gctf} option.
+@end defmac
+
+@need 2000
+@node BTF Debug
+@subsection Macros for BTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for BTF debug format.
+
+@defmac BTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in BTF debug
+format in response to the @option{-gbtf} option.
+@end defmac
+
 @node Floating Point
 @section Cross Compilation and Floating Point
 @cindex cross compilation and floating point