match: `a CMP nonnegative ? a : ABS<a>` simplified to just `ABS<a>` [PR112392]

We can optimize `a == nonnegative ? a : ABS<a>`, `a > nonnegative ? a : ABS<a>`
and `a >= nonnegative ? a : ABS<a>` into `ABS<a>`. This allows removal of
some extra comparison and extra conditional moves in some cases.
I don't remember where I had found though but it is simple to add so
let's add it.

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

Note I have a secondary pattern for the equal case as either a or nonnegative
could be used.

	PR tree-optimization/112392

gcc/ChangeLog:

	* match.pd (`x CMP nonnegative ? x : ABS<x>`): New pattern;
	where CMP is ==, > and >=.
	(`x CMP nonnegative@y ? y : ABS<x>`): New pattern.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-41.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

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