diff --git a/gcc/ChangeLog.asan b/gcc/ChangeLog.asan
index 704aa61..d13a584 100644
--- a/gcc/ChangeLog.asan
+++ b/gcc/ChangeLog.asan
@@ -1,3 +1,21 @@
+2012-10-11  Jakub Jelinek  <jakub@redhat.com>
+
+	* 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.
+
 2012-10-10  Wei Mi <wmi@google.com>
 	    Diego Novillo <dnovillo@google.com>
 	    Dodji Seketeli <dodji@redhat.com>
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 3bade7f..c86bbeb 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2210,7 +2210,7 @@ stor-layout.o : stor-layout.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) \
 asan.o : asan.c asan.h $(CONFIG_H) pointer-set.h \
    $(SYSTEM_H) $(TREE_H) $(GIMPLE_H) \
    output.h $(DIAGNOSTIC_H) coretypes.h $(TREE_DUMP_H) $(FLAGS_H) \
-   tree-pretty-print.h
+   tree-pretty-print.h $(TARGET_H)
 tree-ssa-tail-merge.o: tree-ssa-tail-merge.c \
    $(SYSTEM_H) $(CONFIG_H) coretypes.h $(TM_H) $(BITMAP_H) \
    $(FLAGS_H) $(TM_P_H) $(BASIC_BLOCK_H) \
diff --git a/gcc/asan.c b/gcc/asan.c
index 4b07c96..6cd9625 100644
--- a/gcc/asan.c
+++ b/gcc/asan.c
@@ -1,5 +1,5 @@
 /* AddressSanitizer, a fast memory error detector.
-   Copyright (C) 2011 Free Software Foundation, Inc.
+   Copyright (C) 2011, 2012 Free Software Foundation, Inc.
    Contributed by Kostya Serebryany <kcc@google.com>
 
 This file is part of GCC.
@@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple.h"
 #include "asan.h"
 #include "gimple-pretty-print.h"
+#include "target.h"
 
 /*
  AddressSanitizer finds out-of-bounds and use-after-free bugs 
@@ -78,15 +79,6 @@ along with GCC; see the file COPYING3.  If not see
  to create redzones for stack and global object and poison them.
 */
 
-/* The shadow address is computed as (X>>asan_scale) + (1<<asan_offset_log).
- We may want to add command line flags to change these values.  */
-
-static const int asan_scale = 3;
-static const int asan_offset_log_32 = 29;
-static const int asan_offset_log_64 = 44;
-static int asan_offset_log;
-
-
 /* Construct a function tree for __asan_report_{load,store}{1,2,4,8,16}.
    IS_STORE is either 1 (for a store) or 0 (for a load).
    SIZE_IN_BYTES is one of 1, 2, 4, 8, 16.  */
@@ -202,15 +194,13 @@ build_check_stmt (tree base,
   gimple_set_location (g, location);
   gimple_seq_add_stmt (&seq, g);
 
-  /* Build (base_addr >> asan_scale) + (1 << asan_offset_log).  */
+  /* Build
+     (base_addr >> ASAN_SHADOW_SHIFT) | targetm.asan_shadow_offset ().  */
 
   t = build2 (RSHIFT_EXPR, uintptr_type, base_addr,
-              build_int_cst (uintptr_type, asan_scale));
+	      build_int_cst (uintptr_type, ASAN_SHADOW_SHIFT));
   t = build2 (PLUS_EXPR, uintptr_type, t,
-              build2 (LSHIFT_EXPR, uintptr_type,
-                      build_int_cst (uintptr_type, 1),
-                      build_int_cst (uintptr_type, asan_offset_log)
-                     ));
+	      build_int_cst (uintptr_type, targetm.asan_shadow_offset ()));
   t = build1 (INDIRECT_REF, shadow_type,
               build1 (VIEW_CONVERT_EXPR, shadow_ptr_type, t));
   t = force_gimple_operand (t, &stmts, false, NULL_TREE);
@@ -367,9 +357,6 @@ static unsigned int
 asan_instrument (void)
 {
   struct gimplify_ctx gctx;
-  tree uintptr_type = lang_hooks.types.type_for_mode (ptr_mode, true);
-  int is_64 = tree_low_cst (TYPE_SIZE (uintptr_type), 0) == 64;
-  asan_offset_log = is_64 ? asan_offset_log_64 : asan_offset_log_32;
   push_gimplify_context (&gctx);
   transform_statements ();
   pop_gimplify_context (NULL);
diff --git a/gcc/asan.h b/gcc/asan.h
index 590cf35..699820b 100644
--- a/gcc/asan.h
+++ b/gcc/asan.h
@@ -1,5 +1,5 @@
 /* AddressSanitizer, a fast memory error detector.
-   Copyright (C) 2011 Free Software Foundation, Inc.
+   Copyright (C) 2011, 2012 Free Software Foundation, Inc.
    Contributed by Kostya Serebryany <kcc@google.com>
 
 This file is part of GCC.
@@ -23,4 +23,8 @@ along with GCC; see the file COPYING3.  If not see
 
 extern void asan_finish_file(void);
 
+/* Shadow memory is found at
+   (address >> ASAN_SHADOW_SHIFT) | targetm.asan_shadow_offset ().  */
+#define ASAN_SHADOW_SHIFT	3
+
 #endif /* TREE_ASAN */
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fae300e..881c955 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -5647,6 +5647,14 @@ ix86_legitimate_combined_insn (rtx insn)
   return true;
 }
 
+/* Implement the TARGET_ASAN_SHADOW_OFFSET hook.  */
+
+static unsigned HOST_WIDE_INT
+ix86_asan_shadow_offset (void)
+{
+  return (unsigned HOST_WIDE_INT) 1 << (TARGET_LP64 ? 44 : 29);
+}
+
 /* Argument support functions.  */
 
 /* Return true when register may be used to pass function parameters.  */
@@ -41379,6 +41387,9 @@ ix86_memmodel_check (unsigned HOST_WIDE_INT val)
 #undef TARGET_LEGITIMATE_COMBINED_INSN
 #define TARGET_LEGITIMATE_COMBINED_INSN ix86_legitimate_combined_insn
 
+#undef TARGET_ASAN_SHADOW_OFFSET
+#define TARGET_ASAN_SHADOW_OFFSET ix86_asan_shadow_offset
+
 #undef TARGET_GIMPLIFY_VA_ARG_EXPR
 #define TARGET_GIMPLIFY_VA_ARG_EXPR ix86_gimplify_va_arg
 
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 665c5b1..908ddbf 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -11326,6 +11326,12 @@ MIPS, where add-immediate takes a 16-bit signed value,
 is zero, which disables this optimization.
 @end deftypevr
 
+@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_ASAN_SHADOW_OFFSET (void)
+Return the offset bitwise ored into shifted address to get corresponding
+Address Sanitizer shadow memory address.  NULL if Address Sanitizer is not
+supported by the target.
+@end deftypefn
+
 @deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_MEMMODEL_CHECK (unsigned HOST_WIDE_INT @var{val})
 Validate target specific memory model mask bits. When NULL no target specific
 memory model bits are allowed.
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 289934b..0786691 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -11168,6 +11168,8 @@ MIPS, where add-immediate takes a 16-bit signed value,
 is zero, which disables this optimization.
 @end deftypevr
 
+@hook TARGET_ASAN_SHADOW_OFFSET
+
 @hook TARGET_MEMMODEL_CHECK
 Validate target specific memory model mask bits. When NULL no target specific
 memory model bits are allowed.
diff --git a/gcc/target.def b/gcc/target.def
index 5865224..f8781a8 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -2025,6 +2025,17 @@ DEFHOOK
  "",
  unsigned HOST_WIDE_INT, (unsigned HOST_WIDE_INT val), NULL)
 
+/* Defines an offset bitwise ored into shifted address to get corresponding
+   Address Sanitizer shadow address, or -1 if Address Sanitizer is not
+   supported by the target.  */
+DEFHOOK
+(asan_shadow_offset,
+ "Return the offset bitwise ored into shifted address to get corresponding\n\
+Address Sanitizer shadow memory address.  NULL if Address Sanitizer is not\n\
+supported by the target.",
+ unsigned HOST_WIDE_INT, (void),
+ NULL)
+
 /* Functions relating to calls - argument passing, returns, etc.  */
 /* Members of struct call have no special macro prefix.  */
 HOOK_VECTOR (TARGET_CALLS, calls)
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 3ca0736..68849f5 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1541,6 +1541,13 @@ process_options (void)
       flag_omit_frame_pointer = 0;
     }
 
+  /* Address Sanitizer needs porting to each target architecture.  */
+  if (flag_asan && targetm.asan_shadow_offset == NULL)
+    {
+      warning (0, "-fasan not supported for this target");
+      flag_asan = 0;
+    }
+
   /* Enable -Werror=coverage-mismatch when -Werror and -Wno-error
      have not been set.  */
   if (!global_options_set.x_warnings_are_errors
