x32 Fast tracepoints: IPA target descriptions

x32 Fast tracepoints: IPA target descriptions

Building GDB for x32 fails building the IPA, with:

   .../src/gdb/gdbserver/linux-amd64-ipa.c: In function ‘const target_desc* get_ipa_tdesc(int)’:
   .../src/gdb/gdbserver/linux-amd64-ipa.c:182:14: error: ‘tdesc_amd64_avx_linux’ was not declared in this scope
	  return tdesc_amd64_avx_linux;
		 ^
   .../src/gdb/gdbserver/linux-amd64-ipa.c:184:14: error: ‘tdesc_amd64_mpx_linux’ was not declared in this scope
	  return tdesc_amd64_mpx_linux;
		 ^
   .../src/gdb/gdbserver/linux-amd64-ipa.c:186:14: error: ‘tdesc_amd64_avx_mpx_linux’ was not declared in this scope
	  return tdesc_amd64_avx_mpx_linux;
		 ^
  [...]

The problem is that the IPA is trying to use the 64-bit descriptions,
when it should be using the x32 ones.

gdb/gdbserver/ChangeLog:
2016-08-19  Pedro Alves  <palves@redhat.com>

	PR gdb/20415
	* Makefile.in (x32-linux-ipa.o, x32-avx-linux-ipa.o)
	(x32-avx512-linux-ipa.o): New rules.
	* configure.ac (x86_64-*-linux*): New x32 check.
	* configure.srv (ipa_x32_linux_regobj): New.
	(x86_64-*-linux*): Use $ipa_x32_linux_regobj if building for x32.
	* linux-amd64-ipa.c (get_ipa_tdesc) [__ILP32__]: Return x32
	descriptions.
	(initialize_low_tracepoint) [__ILP32__]: Initialize x32
	descriptions.
	* configure: Regenerate.