combine: Narrow comparison of memory and constant

Comparisons between memory and constants might be done in a smaller mode
resulting in smaller constants which might finally end up as immediates
instead of in the literal pool.

For example, on s390x a non-symmetric comparison like
  x <= 0x3fffffffffffffff
results in the constant being spilled to the literal pool and an 8 byte
memory comparison is emitted.  Ideally, an equivalent comparison
  x0 <= 0x3f
where x0 is the most significant byte of x, is emitted where the
constant is smaller and more likely to materialize as an immediate.

Similarly, comparisons of the form
  x >= 0x4000000000000000
can be shortened into x0 >= 0x40.

gcc/ChangeLog:

	* combine.cc (simplify_compare_const): Narrow comparison of
	memory and constant.
	(try_combine): Adapt new function signature.
	(simplify_comparison): Adapt new function signature.

gcc/testsuite/ChangeLog:

	* gcc.dg/cmp-mem-const-1.c: New test.
	* gcc.dg/cmp-mem-const-2.c: New test.
	* gcc.dg/cmp-mem-const-3.c: New test.
	* gcc.dg/cmp-mem-const-4.c: New test.
	* gcc.dg/cmp-mem-const-5.c: New test.
	* gcc.dg/cmp-mem-const-6.c: New test.
	* gcc.target/s390/cmp-mem-const-1.c: New test.

0 files changed, 0 insertions, 0 deletions