re PR target/26427 (with -fsection-anchors with zero sized structs)

	PR target/26427
	PR target/33120
	PR testsuite/35710

gcc:
	* config/i386/darwin.h (ASM_OUTPUT_COMMON): Remove
	(ASM_OUTPUT_LOCAL): Likewise.
	* config/darwin-protos.h (darwin_asm_declare_object_name): New.
	(darwin_output_aligned_bss): Likewise.
	(darwin_asm_output_aligned_decl_local): Likewise.
	(darwin_asm_output_aligned_decl_common): Likewise.
	(darwin_use_anchors_for_symbol_p): Likewise.
	* config/rs6000/darwin.h (ASM_OUTPUT_COMMON): Remove.
	(TARGET_ASM_OUTPUT_ANCHOR): Define.
	(TARGET_USE_ANCHORS_FOR_SYMBOL_P): Define.
	(DARWIN_SECTION_ANCHORS): Set to 1.
	* config/darwin.c (emit_aligned_common): New var.
	(darwin_init_sections): Check that the Darwin private zero-size section
	marker is in range.
	(darwin_text_section): Check for zero-sized objects.
	(darwin_mergeable_string_section): Likewise.
	(darwin_mergeable_constant_section): Likewise.
	(machopic_select_section): Adjust to check for zero-sized objects.
	Assert that OBJC meta data are non-zero sized.
	(darwin_asm_declare_object_name): New.
	(darwin_asm_declare_constant_name): Adjust for zero-sized
	object sections.
	(BYTES_ZFILL): Define.
	(darwin_emit_weak_or_comdat): New.
	(darwin_emit_local_bss): New.
	(darwin_emit_common): New.
	(darwin_output_aligned_bss): New.
	(darwin_asm_output_aligned_decl_common): New.
	(darwin_asm_output_aligned_decl_local): New.
	(darwin_file_end): Disable subsections_via_symbols when section
	anchoring is active.
	(darwin_asm_output_anchor): Re-enable.
	(darwin_use_anchors_for_symbol_p): New.
	(darwin_override_options): Check for versions that can emit
	aligned common.  Update usage of flags to current.
	* config/darwin-sections.def: Update comments and flags for
	non-anchor sections.  zobj_const_section, zobj_data_section,
	zobj_bss_section, zobj_const_data_section: New.
	* config/darwin.h (ASM_DECLARE_OBJECT_NAME): Redefine.
	(ASM_OUTPUT_ALIGN): Make whitespace output consistent.
	(L2_MAX_OFILE_ALIGNMENT): Define.
	(ASM_OUTPUT_ALIGNED_BSS): Define.
	(ASM_OUTPUT_ALIGNED_DECL_LOCAL): Define.
	(ASM_OUTPUT_ALIGNED_DECL_COMMON): Define.
	(SECTION_NO_ANCHOR): Define.
	(TARGET_ASM_OUTPUT_ANCHOR) Define with a default of NULL.
	(DARWIN_SECTION_ANCHORS): Define with a default of 0.

boehm-gc:
	* dyn_load.c (GC_register_dynamic_libraries/DARWIN):  Add new writable
	data section names.
	(GC_dyld_name_for_hdr): Adjust layout.
	(GC_dyld_image_add): Adjust layout, add new Darwin sections, adjust
	debug to name the sections.
	(GC_dyld_image_remove): Adjust layout, remove new Darwin sections,
	adjust debug to name the sections.
	(GC_register_dynamic_libraries): Adjust layout.
	(GC_init_dyld): Likewise.
	(GC_register_main_static_data): Likewise.

gcc/testsuite:
	* gcc.target/powerpc/darwin-abi-12.c: Adjust for new allocators.
	* gcc.dg/pr26427.c: Remove redundant warning for powerpc.
	* gcc.dg/darwin-comm.c: Adjust for new allocators.
	* gcc.dg/darwin-sections.c: New test.
	* g++.dg/ext/instantiate2.C: Adjust for new allocators.


Co-Authored-By: Mike Stump <mrs@gcc.gnu.org>

From-SVN: r167242