aarch64: Enforce P/M/E order for MOPS instructions

The MOPS instructions should be used as a triple, such as:

       cpyfp [x0]!, [x1]!, x2!
       cpyfm [x0]!, [x1]!, x2!
       cpyfe [x0]!, [x1]!, x2!

The registers should also be the same for each writeback operand.
This patch adds a warning for code that doesn't follow this rule,
along similar lines to the warning that we already emit for
invalid uses of MOVPRFX.

include/
	* opcode/aarch64.h (C_SCAN_MOPS_P, C_SCAN_MOPS_M, C_SCAN_MOPS_E)
	(C_SCAN_MOPS_PME): New macros.
	(AARCH64_OPDE_A_SHOULD_FOLLOW_B): New aarch64_operand_error_kind.
	(AARCH64_OPDE_EXPECTED_A_AFTER_B): Likewise.
	(aarch64_operand_error): Make each data value a union between
	an int and a string.

opcodes/
	* aarch64-tbl.h (MOPS_CPY_OP1_OP2_INSN): Add scan flags.
	(MOPS_SET_OP1_OP2_INSN): Likewise.
	* aarch64-opc.c (set_out_of_range_error): Update after change to
	aarch64_operand_error.
	(set_unaligned_error, set_reg_list_error): Likewise.
	(init_insn_sequence): Use a 3-instruction sequence for
	MOPS P instructions.
	(verify_mops_pme_sequence): New function.
	(verify_constraints): Call it.
	* aarch64-dis.c (print_verifier_notes): Handle
	AARCH64_OPDE_A_SHOULD_FOLLOW_B and AARCH64_OPDE_EXPECTED_A_AFTER_B.

gas/
	* config/tc-aarch64.c (operand_mismatch_kind_names): Add entries
	for AARCH64_OPDE_A_SHOULD_FOLLOW_B and AARCH64_OPDE_EXPECTED_A_AFTER_B.
	(operand_error_higher_severity_p): Check that
	AARCH64_OPDE_A_SHOULD_FOLLOW_B and AARCH64_OPDE_EXPECTED_A_AFTER_B
	come between AARCH64_OPDE_RECOVERABLE and AARCH64_OPDE_SYNTAX_ERROR;
	their relative order is not significant.
	(record_operand_error_with_data): Update after change to
	aarch64_operand_error.
	(output_operand_error_record): Likewise.  Handle
	AARCH64_OPDE_A_SHOULD_FOLLOW_B and AARCH64_OPDE_EXPECTED_A_AFTER_B.
	* testsuite/gas/aarch64/mops_invalid_2.s,
	testsuite/gas/aarch64/mops_invalid_2.d,
	testsuite/gas/aarch64/mops_invalid_2.l: New test.

include/opcode/aarch64.h

@@ -927,7 +927,11 @@ extern const aarch64_opcode aarch64_opcode_table[];
 /* This instruction's operation width is determined by the operand with the
    largest element size.  */
 #define C_MAX_ELEM (1U << 1)
-/* Next bit is 2.  */
+#define C_SCAN_MOPS_P (1U << 2)
+#define C_SCAN_MOPS_M (2U << 2)
+#define C_SCAN_MOPS_E (3U << 2)
+#define C_SCAN_MOPS_PME (3U << 2)
+/* Next bit is 4.  */
 
 static inline bool
 alias_opcode_p (const aarch64_opcode *opcode)
@@ -1221,6 +1225,17 @@ struct aarch64_inst
      Less severe error found during the parsing, very possibly because that
      GAS has picked up a wrong instruction template for the parsing.
 
+   AARCH64_OPDE_A_SHOULD_FOLLOW_B
+     The instruction forms (or is expected to form) part of a sequence,
+     but the preceding instruction in the sequence wasn't the expected one.
+     The message refers to two strings: the name of the current instruction,
+     followed by the name of the expected preceding instruction.
+
+   AARCH64_OPDE_EXPECTED_A_AFTER_B
+     Same as AARCH64_OPDE_A_SHOULD_FOLLOW_B, but shifting the focus
+     so that the current instruction is assumed to be the incorrect one:
+     "since the previous instruction was B, the current one should be A".
+
    AARCH64_OPDE_SYNTAX_ERROR
      General syntax error; it can be either a user error, or simply because
      that GAS is trying a wrong instruction template.
@@ -1255,11 +1270,8 @@ struct aarch64_inst
      Error of the highest severity and used for any severe issue that does not
      fall into any of the above categories.
 
-   The enumerators are only interesting to GAS.  They are declared here (in
-   libopcodes) because that some errors are detected (and then notified to GAS)
-   by libopcodes (rather than by GAS solely).
-
-   The first three errors are only deteced by GAS while the
+   AARCH64_OPDE_RECOVERABLE, AARCH64_OPDE_SYNTAX_ERROR and
+   AARCH64_OPDE_FATAL_SYNTAX_ERROR are only deteced by GAS while the
    AARCH64_OPDE_INVALID_VARIANT error can only be spotted by libopcodes as
    only libopcodes has the information about the valid variants of each
    instruction.
@@ -1273,6 +1285,8 @@ enum aarch64_operand_error_kind
 {
   AARCH64_OPDE_NIL,
   AARCH64_OPDE_RECOVERABLE,
+  AARCH64_OPDE_A_SHOULD_FOLLOW_B,
+  AARCH64_OPDE_EXPECTED_A_AFTER_B,
   AARCH64_OPDE_SYNTAX_ERROR,
   AARCH64_OPDE_FATAL_SYNTAX_ERROR,
   AARCH64_OPDE_INVALID_VARIANT,
@@ -1290,7 +1304,11 @@ struct aarch64_operand_error
   enum aarch64_operand_error_kind kind;
   int index;
   const char *error;
-  int data[3];	/* Some data for extra information.  */
+  /* Some data for extra information.  */
+  union {
+    int i;
+    const char *s;
+  } data[3];
   bool non_fatal;
 };