[patch, aarch64] additional bics patterns

[Sandra Loosemore]

This patch to the AArch64 back end adds a couple of additional bics 
patterns to match code of the form

   if ((x & y) == x) ...;

This is testing whether the bits set in x are a subset of the bits set 
in y; or, that no bits in x are set that are not set in y.  So, it is 
equivalent to

   if ((x & ~y) == 0) ...;

Presently this generates code like
   and     x21, x21, x20
   cmp     x21, x20
   b.eq    c0 <main+0xc0>

and this patch allows it to be written more concisely as:
   bics     x21, x20, x21
   b.eq     c0 <main+0xc0>

Since the bics instruction sets the condition codes itself, no explicit 
comparison is required and the result of the bics computation can be 
discarded.

Regression-tested on aarch64-linux-gnu.  OK to commit?

-Sandra


2014-11-12  Sandra Loosemore  <sandra@codesourcery.com>
	    Chris Jones <chrisj@nvidia.com>

	gcc/
	* config/aarch64/aarch64.md (*and<mode>3_compare_op1): New.
	(*and<mode>3_compare_op2): New.

	gcc/testsuite/
	* gcc.target/aarch64/bics_3.c: New.


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