Rewrite VCEs of integral types [PR116939]

Like the patch to phiopt (r15-4033-g1f619fe25925a5f7), this adds rewriting
of VCE to gimple_with_undefined_signed_overflow/rewrite_to_defined_overflow.
In the case of moving VCE of a bool from being conditional to unconditional,
it needs to be rewritten to not to use VCE but a normal cast. pr120122-1.c is
an example of where LIM needs this rewriting. The precision of the outer type
needs to be less then the inner one.

This also renames gimple_with_undefined_signed_overflow to gimple_needing_rewrite_undefined
and rewrite_to_defined_overflow to rewrite_to_defined_unconditional as they will be doing
more than just handling signed overflow.

Changes since v1:
* v2: rename the functions.
* v3: Add check for precision to be smaller.

Bootstrappd and tested on x86_64-linux-gnu.

	PR tree-optimization/120122
	PR tree-optimization/116939

gcc/ChangeLog:

	* gimple-fold.h (gimple_with_undefined_signed_overflow): Rename to ..
	(rewrite_to_defined_overflow): This.
	(gimple_needing_rewrite_undefined): Rename to ...
	(rewrite_to_defined_unconditional): this.
	* gimple-fold.cc (gimple_with_undefined_signed_overflow): Rename to ...
	(gimple_needing_rewrite_undefined): This. Return true for VCE with integral
	types of smaller precision.
	(rewrite_to_defined_overflow): Rename to ...
	(rewrite_to_defined_unconditional): This. Handle VCE rewriting to a cast.
	* tree-if-conv.cc: s/gimple_with_undefined_signed_overflow/gimple_needing_rewrite_undefined/
	s/rewrite_to_defined_overflow/rewrite_to_defined_unconditional.
	* tree-scalar-evolution.cc: Likewise
	* tree-ssa-ifcombine.cc: Likewise.
	* tree-ssa-loop-im.cc: Likewise.
	* tree-ssa-loop-split.cc: Likewise.
	* tree-ssa-reassoc.cc: Likewise.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr120122-1.c: New test.

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

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