tree: Fix up get_narrower [PR96549]

tree: Fix up get_narrower [PR96549]

My changes to get_narrower to support COMPOUND_EXPRs apparently
used a wrong type for the COMPOUND_EXPRs, while e.g. the rhs
type was unsigned short, the COMPOUND_EXPR got int type as that was the
original type of op.  The type of COMPOUND_EXPR should be always the type
of the rhs.

2020-08-11  Jakub Jelinek  <jakub@redhat.com>

	PR c/96549
	* tree.c (get_narrower): Use TREE_TYPE (ret) instead of
	TREE_TYPE (win) for COMPOUND_EXPRs.

	* gcc.c-torture/execute/pr96549.c: New test.