md.texi: Document that the % constraint character must be at the beginning of the...

md.texi: Document that the % constraint character must be at the beginning of the string.

gcc/
	* doc/md.texi: Document that the % constraint character must
	be at the beginning of the string.
	* genoutput.c (validate_insn_alternatives): Check that '=',
	'+' and '%' only appear at the beginning of a constraint.
	* ira.c (commutative_constraint_p): Delete.
	(ira_get_dup_out_num): Expect the '%' commutativity marker to be
	at the start of the string.
	* config/alpha/alpha.md (*movmemdi_1, *clrmemdi_1): Remove
	duplicate '='s.
	* config/arm/neon.md (bicdi3_neon): Likewise.
	* config/iq2000/iq2000.md (addsi3_internal, subsi3_internal, sgt_si)
	(slt_si, sltu_si): Likewise.
	* config/vax/vax.md (sbcdi3): Likewise.
	* config/h8300/h8300.md (*cmpstz): Remove duplicate '+'.
	* config/arc/arc.md (mulsi_600, mulsidi_600, umulsidi_600)
	(mul64): Move '%' to beginning of constraint.
	* config/arm/arm.md (*xordi3_insn): Likewise.
	* config/nds32/nds32.md (add<mode>3, mulsi3, andsi3, iorsi3)
	(xorsi3): Likewise.

From-SVN: r211031