RFC: Patch to implement Aarch64 SIMD ABI

[Steve Ellcey]

Here is version 3 of my patch to implement the SIMD ABI on Aarch64.
I am having a problem with how to handle a SIMD function calling a
non-SIMD function.  When this happens the SIMD function needs to save
V8 to V23 because it cannot count on the non-SIMD function to save
all 128 bits of these registers.

I thought I had this working in the last patch but as I write test
cases, it appears that it is not working and I am not sure how to
implement it.  I tried adding clobbers in aarch64_expand_call but
that is not working (see code in this patch in aarch64_expand_call).
If I add them to 'call' which is a parallel insn, they are ignored.
If I find the underlying call instruction that is part of the parallel
then the clobbers get added to the instruction but then the call itself
is not recognized with the extra clobbers in place.  I don't think we
want to add new call instructions in aarch64.md to handle the vector
register saves and restores.  Am I trying to add the clobbers in the
wrong place?  Where and when should extra clobbers be added to a call
that is going to clobber more registers than what is indicated by
CALL_USED_REGISTERS?

I suppose I could use TARGET_HARD_REGNO_CALL_PART_CLOBBERED but I would
have to extend it to include the call instruction as an argument so the
the code could determine if the call being made was to a simd or non-simd
function.

Steve Ellcey
sellcey@cavium.com


2018-07-25  Steve Ellcey  <sellcey@cavium.com>

	* config/aarch64/aarch64.c (aarch64_attribute_table): New array.
	(aarch64_simd_decl_p): New function.
	(aarch64_reg_save_mode): New function.
	(aarch64_is_simd_call_p): New function.
	(aarch64_function_ok_for_sibcall): Check for simd calls.
	(aarch64_layout_frame): Check for simd function.
	(aarch64_gen_storewb_pair): Handle E_TFmode.
	(aarch64_push_regs): Use aarch64_reg_save_mode to get mode.
	(aarch64_gen_loadwb_pair): Handle E_TFmode.
	(aarch64_pop_regs): Use aarch64_reg_save_mode to get mode.
	(aarch64_components_for_bb): Check for simd function.
	(aarch64_process_components): Ditto.
	(aarch64_expand_prologue): Ditto.
	(aarch64_expand_epilogue): Ditto.
	(aarch64_expand_call): Ditto.
	(TARGET_ATTRIBUTE_TABLE): New define.
	* config/aarch64/aarch64.h (REG_ALLOC_ORDER): New define.
	(HONOR_REG_ALLOC_ORDER): Ditto.
	(FP_SIMD_SAVED_REGNUM_P): Ditto.
	* config/aarch64/aarch64.md (V23_REGNUM) New constant.
	(loadwb_pair<TX:mode>_<P:mode>): New instruction.
	("storewb_pair<TX:mode>_<P:mode>): Ditto.
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