[ARC] Fix detection of long immediate for load/store operands.

[ARC] Fix detection of long immediate for load/store operands.

ARC can use scaled offsets when loading (i.e. ld.as rA,[base,
offset]).  Where base and offset can be a register or an immediate
operand.  The scaling only applies on the offset part of the
instruction.  The compiler can accept an address like this:

(plus:SI (mult:SI (reg:SI 2 r2 [orig:596 _2129 ] [596])
	          (const_int 4 [0x4]))
	 (const_int 60 [0x3c]))

Hence, to emit this instruction we place the (const_int 60) into base
and the register into offset to take advantage of the scaled offset
facility of the load instruction.  As a result the length of the load
instruction is 8 bytes.  However, the long_immediate_loadstore_operand
predicate used for calculating the length attribute doesn't recognize
this address and returns a wrong decision leading to a wrong length
computation for a load instruction using the above address.

gcc/
2017-03-27  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/predicates.md (long_immediate_loadstore_operand):
	Consider scaled addresses cases.

From-SVN: r246496