MATCH: Support `(a != (CST+1)) & (a > CST)` optimizations

Even though this is done via reassocation, match can support
these with a simple change to detect that the difference is just
one. This allows to optimize these earlier and even during phiopt
for an example.

This patch adds the following cases:
(a != (CST+1)) & (a > CST) -> a > (CST+1)
(a != (CST-1)) & (a < CST) -> a < (CST-1)
(a == (CST-1)) | (a >= CST) -> a >= (CST-1)
(a == (CST+1)) | (a <= CST) -> a <= (CST+1)

Canonicalizations of comparisons causes this case to show up more.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/106164

gcc/ChangeLog:

	* match.pd (`(X CMP1 CST1) AND/IOR (X CMP2 CST2)`):
	Expand to support constants that are off by one.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr21643.c: Update test now that match does
	the combing of the comparisons.
	* gcc.dg/tree-ssa/cmpbit-5.c: New test.
	* gcc.dg/tree-ssa/phi-opt-35.c: New test.

0 files changed, 0 insertions, 0 deletions