Use NSDMI for predicate class

From _1 < _2 we conclude [-INF, +INF - 1] and invert it as [+INF, +INF] -
oops.  Compute the other edge range explicitely.

This applies a workaround to avoid unswitching on predicates from
BBs that are considered unreachable and to that effect makes sure
to always cost bb[0] which we always put on the worklist as reachable.

Using global ranges and inverting them is not correct - in the
particular case we ended up with a global range from a if (a_1 = b_2)
predicate and used the inversion on the false edge.  The change
refactors the predicate CTORs again, using range-ops to create a bare
range from the comparison in the GIMPLE_COND only and for switches
resorts to computing the ranges manually by unioning the case ranges.

The ranger query in the simplification code should probably change
as well to use a path_range_query where we should seed the path
range oracle with the predicate stack of the loop version we want
to simplify.

Bootstraps OK, has

FAIL: gfortran.fortran-torture/execute/forall_7.f90 execution,  -O3 -g

and ICEs 511.povray_r, 526.blender_r, 538.imagick_r with -Ofast znver2

splines.cpp:687:5: internal compiler error: in tree_unswitch_single_loop, at tree-ssa-loop-unswitch.cc:902

blender/source/blender/modifiers/intern/MOD_weightvg_util.c:120:6: internal compiler error: Segmentation fault

magick/composite.c:1631:32: internal compiler error: in tree_unswitch_single_loop, at tree-ssa-loop-unswitch.cc:902

the 902 is the size estimation assert recently added.

duplicate_loop_body_to_header_edge clears bb->aux which is not wanted
by a new use in loop unswitching.  The clearing was introduced with
r0-69110-g6580ee7781f903 and it seems accidentially so.

2022-05-17  Richard Biener  <rguenther@suse.de>

	* cfgloopmanip.cc (duplicate_loop_body_to_header_edge): Do
	not clear bb->aux of the copied blocks.

When registering a relation, we need to merge with any existing relation
before checking if it was an equivalence... otherwise it was not being
handled properly.

	gcc/
	PR tree-optimization/105458
	* value-relation.cc (path_oracle::register_relation): Merge, then check
	for equivalence.

	gcc/testsuite/
	* gcc.dg/pr105458.c: New.