PR debug/82933
	* run-rtl-passes.c: Include debug.h.
	(run_rtl_passes): Call debug_hooks->assembly_start.
	* dwarf2out.c (dwarf2out_assembly_start): Return early if invoked
	multiple times.

	* gcc.dg/rtl/x86_64/pr82933.c: New test.

From-SVN: r254987