Hi,

this patch is aimed at cleaning up the mess with the RTL libfunc machinery.

On the one hand you have comments like these in the RTL expander:

  /* It is incorrect to use the libcall calling conventions to call
     memcpy in this context.  This could be a user call to memcpy and
     the user may wish to examine the return value from memcpy.  For
     targets where libcalls and normal calls have different conventions
     for returning pointers, we could end up generating incorrect code.  */

  /* It is incorrect to use the libcall calling conventions to call
     memset in this context.  This could be a user call to memset and
     the user may wish to examine the return value from memset.  For
     targets where libcalls and normal calls have different conventions
     for returning pointers, we could end up generating incorrect code.  */

and on the other hand you have at the end of expand_builtin_memcmp:

  emit_library_call_value (memcmp_libfunc, result, LCT_PURE,
			   TYPE_MODE (integer_type_node), 3,
			   XEXP (arg1_rtx, 0), Pmode,
			   XEXP (arg2_rtx, 0), Pmode,
			   convert_to_mode (TYPE_MODE (sizetype), arg3_rtx,
					    TYPE_UNSIGNED (sizetype)),
			   TYPE_MODE (sizetype));

so the RTL expander is not allowed to call memcpy & memset libfuncs on its own 
but it is for __builtin_memcmp, which is rather inconsistent.

So the patch eliminates all the RTL libfuncs and replaces them by calls to the 
corresponding builtins, except for 3 of them:
  - synchronize_libfunc, which is used by the ARM and MIPS back-ends,
  - unwind_sjlj_register_libfunc, which is used by the SJLJ machinery,
  - unwind_sjlj_unregister_libfunc, likewise.

abort_libfunc and memcmp_libfunc are set by VMS to something else than the 
default but this looks like an optimization and can presumably be dropped.

Bootstrapped/regtested on x86-64/Linux and PowerPC/Linux, OK for mainline?


2016-05-10  Eric Botcazou  <ebotcazou@adacore.com>

	* builtins.c (expand_builtin_memcmp): Do not emit the call here.
	(expand_builtin_trap): Emit a regular call.
	(set_builtin_user_assembler_name): Remove obsolete cases.
	* dse.c (scan_insn): Adjust.
	* except.c: Include calls.h.
	(sjlj_emit_function_enter): If DONT_USE_BUILTIN_SETJMP is defined,
	emit a regular call to setjmp.
	* expr.c (emit_block_move_hints): Call emit_block_copy_via_libcall.
	(block_move_libcall_safe_for_call_parm): Use memcpy builtin.
	(emit_block_move_via_libcall): Delete.
	(block_move_fn): Delete.
	(init_block_move_fn): Likewise.
	(emit_block_move_libcall_fn): Likewise.
	(emit_block_op_via_libcall): New function.
	(set_storage_via_libcall): Tidy up and use memset builtin.
	(block_clear_fn): Delete.
	(init_block_clear_fn): Likewise.
	(clear_storage_libcall_fn): Likewise.
	(expand_assignment): Call emit_block_move_via_libcall.
	Do not include gt-expr.h.
	* expr.h (emit_block_op_via_libcall): Declare.
	(emit_block_copy_via_libcall): New inline function.
	(emit_block_move_via_libcall): Likewise.
	(emit_block_comp_via_libcall): Likewise.
	(block_clear_fn): Delete.
	(init_block_move_fn): Likewise.
	(init_block_clear_fn): Likewise.
	(emit_block_move_via_libcall): Likewise.
	(set_storage_via_libcall): Add default parameter value.
	* libfuncs.h (enum libfunc_index): Remove obsolete values.
	(abort_libfunc): Delete.
	(memcpy_libfunc): Likewise.
	(memmove_libfunc): Likewise.
	(memcmp_libfunc): Likewise.
	(memset_libfunc): Likewise.
	(setbits_libfunc): Likewise.
	(setjmp_libfunc): Likewise.
	(longjmp_libfunc): Likewise.
	(profile_function_entry_libfunc): Likewise.
	(profile_function_exit_libfunc): Likewise.
	(gcov_flush_libfunc): Likewise.
	* optabs-libfuncs.c (build_libfunc_function): Set DECL_ARTIFICIAL
	and DECL_VISIBILITY on the declaration.
	(init_optabs): Do not initialize obsolete libfuncs.
	* optabs.c (prepare_cmp_insn): Call emit_block_comp_via_libcall.
	* tree-core.h (ECF_RET1): Define.
	(ECF_TM_PURE): Adjust.
	(ECF_TM_BUILTIN): Likewise.
	* tree.c (set_call_expr_flags): Deal with ECF_RET1.
	(build_common_builtin_nodes): Initialize abort builtin.
	Add ECF_RET1 on memcpy, memmove and memset builtins.
	Pass final flags for alloca and alloca_with_align builtins.
	* config/alpha/alpha.c (alpha_init_libfuncs): Do not initialize
	obsolete builtins.
	* config/ia64/ia64.c (ia64_vms_init_libfuncs): Likewise.
	* config/i386/i386.c (ix86_expand_set_or_movmem): Adjust call to
	set_storage_via_libcall and call emit_block_copy_via_libcall.

-- 
Eric Botcazou