Fix PR111407--SSA corruption due to widening_mul opt on conflict across an abnormal...

Fix PR111407--SSA corruption due to widening_mul opt on conflict across an abnormal edge

This is a bug in tree-ssa-math-opts.cc, when applying the widening mul
optimization, the compiler needs to check whether the operand is in a
ABNORMAL PHI, if YES, we should avoid the transformation.

	PR tree-optimization/111407

gcc/ChangeLog:

	* tree-ssa-math-opts.cc (convert_mult_to_widen): Avoid the transform
	when one of the operands is subject to abnormal coalescing.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr111407.c: New test.