gcc/
	* tree-cfg.c (gimple_seq_unreachable_p): New function.
	(assert_unreachable_fallthru_edge_p): Use it.
	(group_case_labels_stmt): Likewise.
	* tree-cfg.h: Prototype it.
	* stmt.c: Include cfghooks.h and tree-cfg.h.
	(emit_case_dispatch_table) <gap_label>: New local variable.
	Use it to fill dispatch table gaps.
	Test for default_label before updating probabilities.
	(expand_case) <default_label>: Remove unneeded initialization.
	Test for unreachable default case statement and remove its edge.
	Set default_label accordingly.
	* tree-ssa-ccp.c (optimize_unreachable): Update comment.

gcc/testsuite/
	* gcc.target/powerpc/pr51513.c: New test.
	* gcc.dg/predict-13.c: Replace __builtin_unreachable() with
	__builtin_abort().
	* gcc.dg/predict-14.c: Likewise.

From-SVN: r247844