PR debug/51902

	PR debug/51902
	* tree.h (BLOCK_SAME_RANGE): Define.
	* function.c (block_fragments_nreverse): Clear BLOCK_SAME_RANGE
	if BLOCK_FRAGMENT_CHAIN is non-NULL, but has it cleared.
	Also clear BLOCK_SAME_RANGE if fragment chain's supercontext fragment
	isn't equal to supercontext fragment's fragment chain.
	Adjust BLOCK_SUPERCONTEXT to point to supercontext fragment's
	fragment origin.
	(blocks_nreverse_all): Likewise.
	(reorder_blocks_1): Compute BLOCK_SAME_RANGE bits.  Set
	BLOCK_SUPERCONTEXT to supercontext fragment instead of
	supercontext fragment's fragment origin.
	* dwarf2out.c (add_high_low_attributes): If stmt has the same
	range as its parent (or parents thereof etc.), use the parent's
	DW_AT_ranges value instead of creating a new .debug_ranges range.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@184958 138bc75d-0d04-0410-961f-82ee72b054a4