This patch defines a new asan_shadow_offset target macro, instead of
having a mere macro in the asan.c file.  It becomes thus cleaner to
define the target macro for targets that supports asan, namely x86 for
now.  The ASAN_SHADOW_SHIFT (which, along with the asan_shadow_offset
constant, is used to compute the address of the shadow memory byte for
a given memory address) is defined in asan.h.

gcc/ChangeLog

	* toplev.c (process_options): Warn and turn off
	-faddress-sanitizer if not supported by target.
	* asan.c: Include target.h.
	(asan_scale, asan_offset_log_32, asan_offset_log_64,
	asan_offset_log): Removed.
	(build_check_stmt): Use ASAN_SHADOW_SHIFT and
	targetm.asan_shadow_offset ().
	(asan_instrument): Don't initialize asan_offset_log.
	* asan.h (ASAN_SHADOW_SHIFT): Define.
	* target.def (TARGET_ASAN_SHADOW_OFFSET): New hook.
	* doc/tm.texi.in (TARGET_ASAN_SHADOW_OFFSET): Add it.
	* doc/tm.texi: Regenerated.
	* Makefile.in (asan.o): Depend on $(TARGET_H).
	* config/i386/i386.c (ix86_asan_shadow_offset): New function.
	(TARGET_ASAN_SHADOW_OFFSET): Define.

From-SVN: r193433