[PATCH 5/8][Binutils][AArch64] Add SVE constraints verifier.

[Tamar Christina]

Hi All,

This patch adds the verification rules for move prefix constraints.

The Arm SVE instruction MOVPRFX introduces[1] constraints on the instruction at
PC+4. Particularly the following constraints are handled by this patch

* MOVPRFX must be followed by an instruction.
* MOVPRFX can only be followed by non-layout altering directives.
* MOVPRFX destination register MUST be used as the destination register in the
  instruction at PC+4, and is not allowed to be used in any other position other than
  destructive input.  This includes registers that architecturally overlap. e.g. x1
  should be treated as z1.
* MOVPRFX must be followed by a restricted set of SVE instructions.
* The size of the destination register of MOVPRFX must be equal to that of
  the operation at PC+4.
* The predicate register and operation of MOVPRFX must match that of the instruction
  at PC+4
* The predicated instruction at PC+4 must use the merging predicate.
* Architectural aliases and pseudo-instructions need to be supported as well.
* MOVPRFX cannot be the last instruction in a sequence

Any failure to adhere to any of these constrains will emit an assembly warning
and a disassembly note.

[1] https://developer.arm.com/docs/ddi0584/latest/arm-architecture-reference-manual-supplement-the-scalable-vector-extension-sve-for-armv8-a

build on native hardware and regtested on
  aarch64-none-elf, aarch64-none-elf (32 bit host),
  aarch64-none-linux-gnu

Cross-compiled and regtested on
  aarch64-none-linux-gnu, aarch64_be-none-linux-gnu

and no issues.

Ok for master?

Thanks,
Tamar

include/
2018-09-24  Tamar Christina  <tamar.christina@arm.com>

	* opcode/aarch64.h (aarch64_inst): Remove.
	(enum err_type): Add ERR_VFI.
	(aarch64_is_destructive_by_operands): New.
	(init_insn_sequence): New.
	(aarch64_decode_insn): Remove param name.

opcodes/
2018-09-24  Tamar Christina  <tamar.christina@arm.com>

	* aarch64-opc.c (init_insn_block): New.
	(verify_constraints, aarch64_is_destructive_by_operands): New.
	* aarch64-opc.h (verify_constraints): New.

gas/
2018-09-24  Tamar Christina  <tamar.christina@arm.com>

        * config/tc-aarch64.c (output_operand_error_report): Order warnings.

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