In the case where we access a single bit from a value and use this in a
EQ/NE comparison, GCC will convert this into a sign-extend and GE/LT
comparison.

Normally this would be fine, however, if the value is in CMEM memory,
then we don't have a sign-extending load available (using the special
short CMEM load instructions), and instead we end up using a long form
load with LIMM, which is less efficient.

This peephole optimisation looks for the sign-extend followed by GE/LT
pattern and converts this back into a load and EQ/NE comparison.

gcc/ChangeLog:

	* config/arc/arc.md (cmem bit/sign-extend peephole2): New peephole
	to make better use of cmem loads in the case where a single bit is
	being accessed.
	* config/arc/predicates.md (ge_lt_comparison_operator): New
	predicate.

gcc/testsuite/ChangeLog:

	* gcc.target/arc/cmem-bit-1.c: New file.
	* gcc.target/arc/cmem-bit-2.c: New file.
	* gcc.target/arc/cmem-bit-3.c: New file.
	* gcc.target/arc/cmem-bit-4.c: New file.

From-SVN: r242572