diff --git a/gcc/ChangeLog.asan b/gcc/ChangeLog.asan
new file mode 100644
index 0000000..704aa61
--- /dev/null
+++ b/gcc/ChangeLog.asan
@@ -0,0 +1,12 @@
+2012-10-10  Wei Mi <wmi@google.com>
+	    Diego Novillo <dnovillo@google.com>
+	    Dodji Seketeli <dodji@redhat.com>
+
+	* Makefile.in: Add asan.c and its dependencies.
+	* common.opt: Add -faddress-sanitizer option.
+	* invoke.texi: Document the new flag.
+	* passes.c: Add the asan pass.
+	* toplev.c (compile_file): Call asan_finish_file.
+	* asan.c: New file.
+	* asan.h: New file.
+	* tree-pass.h: Declare pass_asan.
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 9aea03d..3bade7f 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1348,6 +1348,7 @@ OBJS = \
 	tracer.o \
 	trans-mem.o \
 	tree-affine.o \
+	asan.o \
 	tree-call-cdce.o \
 	tree-cfg.o \
 	tree-cfgcleanup.o \
@@ -2206,6 +2207,10 @@ stor-layout.o : stor-layout.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) \
    $(TREE_H) $(PARAMS_H) $(FLAGS_H) $(FUNCTION_H) $(EXPR_H) $(RTL_H) \
    $(GGC_H) $(TM_P_H) $(TARGET_H) langhooks.h $(REGS_H) gt-stor-layout.h \
    $(DIAGNOSTIC_CORE_H) $(CGRAPH_H) $(TREE_INLINE_H) $(TREE_DUMP_H) $(GIMPLE_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-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
new file mode 100644
index 0000000..4b07c96
--- /dev/null
+++ b/gcc/asan.c
@@ -0,0 +1,404 @@
+/* AddressSanitizer, a fast memory error detector.
+   Copyright (C) 2011 Free Software Foundation, Inc.
+   Contributed by Kostya Serebryany <kcc@google.com>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "tm_p.h"
+#include "basic-block.h"
+#include "flags.h"
+#include "function.h"
+#include "tree-inline.h"
+#include "gimple.h"
+#include "tree-iterator.h"
+#include "tree-flow.h"
+#include "tree-dump.h"
+#include "tree-pass.h"
+#include "diagnostic.h"
+#include "demangle.h"
+#include "langhooks.h"
+#include "ggc.h"
+#include "cgraph.h"
+#include "gimple.h"
+#include "asan.h"
+#include "gimple-pretty-print.h"
+
+/*
+ AddressSanitizer finds out-of-bounds and use-after-free bugs 
+ with <2x slowdown on average.
+
+ The tool consists of two parts:
+ instrumentation module (this file) and a run-time library.
+ The instrumentation module adds a run-time check before every memory insn.
+   For a 8- or 16- byte load accessing address X:
+     ShadowAddr = (X >> 3) + Offset
+     ShadowValue = *(char*)ShadowAddr;  // *(short*) for 16-byte access.
+     if (ShadowValue)
+       __asan_report_load8(X);
+   For a load of N bytes (N=1, 2 or 4) from address X:
+     ShadowAddr = (X >> 3) + Offset
+     ShadowValue = *(char*)ShadowAddr;
+     if (ShadowValue)
+       if ((X & 7) + N - 1 > ShadowValue)
+         __asan_report_loadN(X);
+ Stores are instrumented similarly, but using __asan_report_storeN functions.
+ A call too __asan_init() is inserted to the list of module CTORs.
+
+ The run-time library redefines malloc (so that redzone are inserted around
+ the allocated memory) and free (so that reuse of free-ed memory is delayed),
+ provides __asan_report* and __asan_init functions.
+
+ Read more:
+ http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
+
+ Future work:
+ The current implementation supports only detection of out-of-bounds and
+ use-after-free bugs in heap.
+ In order to support out-of-bounds for stack and globals we will need
+ 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.  */
+
+static tree
+report_error_func (int is_store, int size_in_bytes)
+{
+  tree fn_type;
+  tree def;
+  char name[100];
+
+  sprintf (name, "__asan_report_%s%d\n",
+           is_store ? "store" : "load", size_in_bytes);
+  fn_type = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE);
+  def = build_fn_decl (name, fn_type);
+  TREE_NOTHROW (def) = 1;
+  TREE_THIS_VOLATILE (def) = 1;  /* Attribute noreturn. Surprise!  */
+  DECL_ATTRIBUTES (def) = tree_cons (get_identifier ("leaf"), 
+                                     NULL, DECL_ATTRIBUTES (def));
+  DECL_ASSEMBLER_NAME (def);
+  return def;
+}
+
+/* Construct a function tree for __asan_init().  */
+
+static tree
+asan_init_func (void)
+{
+  tree fn_type;
+  tree def;
+
+  fn_type = build_function_type_list (void_type_node, NULL_TREE);
+  def = build_fn_decl ("__asan_init", fn_type);
+  TREE_NOTHROW (def) = 1;
+  DECL_ASSEMBLER_NAME (def);
+  return def;
+}
+
+
+/* Instrument the memory access instruction BASE.
+   Insert new statements before ITER.
+   LOCATION is source code location.
+   IS_STORE is either 1 (for a store) or 0 (for a load).
+   SIZE_IN_BYTES is one of 1, 2, 4, 8, 16.  */
+
+static void
+build_check_stmt (tree base,
+                  gimple_stmt_iterator *iter,
+                  location_t location, int is_store, int size_in_bytes)
+{
+  gimple_stmt_iterator gsi;
+  basic_block cond_bb, then_bb, join_bb;
+  edge e;
+  tree cond, t, u;
+  tree base_addr;
+  tree shadow_value;
+  gimple g;
+  gimple_seq seq, stmts;
+  tree shadow_type = size_in_bytes == 16 ?
+      short_integer_type_node : char_type_node;
+  tree shadow_ptr_type = build_pointer_type (shadow_type);
+  tree uintptr_type = lang_hooks.types.type_for_mode (ptr_mode,
+                                                      /*unsignedp=*/true);
+
+  /* We first need to split the current basic block, and start altering
+     the CFG.  This allows us to insert the statements we're about to
+     construct into the right basic blocks.  */
+
+  cond_bb = gimple_bb (gsi_stmt (*iter));
+  gsi = *iter;
+  gsi_prev (&gsi);
+  if (!gsi_end_p (gsi))
+    e = split_block (cond_bb, gsi_stmt (gsi));
+  else
+    e = split_block_after_labels (cond_bb);
+  cond_bb = e->src;
+  join_bb = e->dest;
+
+  /* A recap at this point: join_bb is the basic block at whose head
+     is the gimple statement for which this check expression is being
+     built.  cond_bb is the (possibly new, synthetic) basic block the
+     end of which will contain the cache-lookup code, and a
+     conditional that jumps to the cache-miss code or, much more
+     likely, over to join_bb.  */
+
+  /* Create the bb that contains the crash block.  */
+  then_bb = create_empty_bb (cond_bb);
+  make_edge (cond_bb, then_bb, EDGE_TRUE_VALUE);
+  make_single_succ_edge (then_bb, join_bb, EDGE_FALLTHRU);
+
+  /* Mark the pseudo-fallthrough edge from cond_bb to join_bb.  */
+  e = find_edge (cond_bb, join_bb);
+  e->flags = EDGE_FALSE_VALUE;
+  e->count = cond_bb->count;
+  e->probability = REG_BR_PROB_BASE;
+
+  /* Update dominance info.  Note that bb_join's data was
+     updated by split_block.  */
+  if (dom_info_available_p (CDI_DOMINATORS))
+    {
+      set_immediate_dominator (CDI_DOMINATORS, then_bb, cond_bb);
+      set_immediate_dominator (CDI_DOMINATORS, join_bb, cond_bb);
+    }
+
+  base_addr = create_tmp_reg (uintptr_type, "__asan_base_addr");
+
+  seq = NULL; 
+  t = fold_convert_loc (location, uintptr_type,
+                        unshare_expr (base));
+  t = force_gimple_operand (t, &stmts, false, NULL_TREE);
+  gimple_seq_add_seq (&seq, stmts);
+  g = gimple_build_assign (base_addr, t);
+  gimple_set_location (g, location);
+  gimple_seq_add_stmt (&seq, g);
+
+  /* Build (base_addr >> asan_scale) + (1 << asan_offset_log).  */
+
+  t = build2 (RSHIFT_EXPR, uintptr_type, base_addr,
+              build_int_cst (uintptr_type, asan_scale));
+  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)
+                     ));
+  t = build1 (INDIRECT_REF, shadow_type,
+              build1 (VIEW_CONVERT_EXPR, shadow_ptr_type, t));
+  t = force_gimple_operand (t, &stmts, false, NULL_TREE);
+  gimple_seq_add_seq (&seq, stmts);
+  shadow_value = create_tmp_reg (shadow_type, "__asan_shadow");
+  g = gimple_build_assign (shadow_value, t);
+  gimple_set_location (g, location);
+  gimple_seq_add_stmt (&seq, g);
+  t = build2 (NE_EXPR, boolean_type_node, shadow_value,
+              build_int_cst (shadow_type, 0));
+  if (size_in_bytes < 8)
+    {
+
+      /* Slow path for 1-, 2- and 4- byte accesses.
+         Build ((base_addr & 7) + (size_in_bytes - 1)) >= shadow_value.  */
+
+      u = build2 (BIT_AND_EXPR, uintptr_type,
+                  base_addr,
+                  build_int_cst (uintptr_type, 7));
+      u = build1 (CONVERT_EXPR, shadow_type, u);
+      u = build2 (PLUS_EXPR, shadow_type, u,
+                  build_int_cst (shadow_type, size_in_bytes - 1));
+      u = build2 (GE_EXPR, uintptr_type, u, shadow_value);
+    }
+  else
+      u = build_int_cst (boolean_type_node, 1);
+  t = build2 (TRUTH_AND_EXPR, boolean_type_node, t, u);
+  t = force_gimple_operand (t, &stmts, false, NULL_TREE);
+  gimple_seq_add_seq (&seq, stmts);
+  cond = create_tmp_reg (boolean_type_node, "__asan_crash_cond");
+  g = gimple_build_assign  (cond, t);
+  gimple_set_location (g, location);
+  gimple_seq_add_stmt (&seq, g);
+  g = gimple_build_cond (NE_EXPR, cond, boolean_false_node, NULL_TREE,
+                         NULL_TREE);
+  gimple_set_location (g, location);
+  gimple_seq_add_stmt (&seq, g);
+
+  /* Generate call to the run-time library (e.g. __asan_report_load8).  */
+
+  gsi = gsi_last_bb (cond_bb);
+  gsi_insert_seq_after (&gsi, seq, GSI_CONTINUE_LINKING);
+  seq = NULL; 
+  g = gimple_build_call (report_error_func (is_store, size_in_bytes),
+                         1, base_addr);
+  gimple_seq_add_stmt (&seq, g);
+
+  /* Insert the check code in the THEN block.  */
+
+  gsi = gsi_start_bb (then_bb);
+  gsi_insert_seq_after (&gsi, seq, GSI_CONTINUE_LINKING);
+
+  *iter = gsi_start_bb (join_bb);
+}
+
+/* If T represents a memory access, add instrumentation code before ITER.
+   LOCATION is source code location.
+   IS_STORE is either 1 (for a store) or 0 (for a load).  */
+
+static void
+instrument_derefs (gimple_stmt_iterator *iter, tree t,
+                  location_t location, int is_store)
+{
+  tree type, base;
+  int size_in_bytes;
+
+  type = TREE_TYPE (t);
+  if (type == error_mark_node)
+    return;
+  switch (TREE_CODE (t))
+    {
+    case ARRAY_REF:
+    case COMPONENT_REF:
+    case INDIRECT_REF:
+    case MEM_REF:
+      break;
+    default:
+      return;
+    }
+  size_in_bytes = tree_low_cst (TYPE_SIZE (type), 0) / BITS_PER_UNIT;
+  if (size_in_bytes != 1 && size_in_bytes != 2 &&
+      size_in_bytes != 4 && size_in_bytes != 8 && size_in_bytes != 16)
+      return;
+  {
+    /* For now just avoid instrumenting bit field acceses.
+     Fixing it is doable, but expected to be messy.  */
+
+    HOST_WIDE_INT bitsize, bitpos;
+    tree offset;
+    enum machine_mode mode;
+    int volatilep = 0, unsignedp = 0;
+    get_inner_reference (t, &bitsize, &bitpos, &offset,
+                         &mode, &unsignedp, &volatilep, false);
+    if (bitpos != 0 || bitsize != size_in_bytes * BITS_PER_UNIT)
+        return;
+  }
+
+  base = build_addr (t, current_function_decl);
+  build_check_stmt (base, iter, location, is_store, size_in_bytes);
+}
+
+/* asan: this looks too complex. Can this be done simpler? */
+/* Transform
+   1) Memory references.
+   2) BUILTIN_ALLOCA calls.
+*/
+
+static void
+transform_statements (void)
+{
+  basic_block bb;
+  gimple_stmt_iterator i;
+  int saved_last_basic_block = last_basic_block;
+  enum gimple_rhs_class grhs_class;
+
+  FOR_EACH_BB (bb)
+    {
+      if (bb->index >= saved_last_basic_block) continue;
+      for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
+        {
+          gimple s = gsi_stmt (i);
+          if (gimple_code (s) != GIMPLE_ASSIGN)
+              continue;
+          instrument_derefs (&i, gimple_assign_lhs (s),
+                             gimple_location (s), 1);
+          instrument_derefs (&i, gimple_assign_rhs1 (s),
+                             gimple_location (s), 0);
+          grhs_class = get_gimple_rhs_class (gimple_assign_rhs_code (s));
+          if (grhs_class == GIMPLE_BINARY_RHS)
+            instrument_derefs (&i, gimple_assign_rhs2 (s),
+                               gimple_location (s), 0);
+        }
+    }
+}
+
+/* Module-level instrumentation.
+   - Insert __asan_init() into the list of CTORs.
+   - TODO: insert redzones around globals.
+ */
+
+void
+asan_finish_file (void)
+{
+  tree ctor_statements = NULL_TREE;
+  append_to_statement_list (build_call_expr (asan_init_func (), 0),
+                            &ctor_statements);
+  cgraph_build_static_cdtor ('I', ctor_statements,
+                             MAX_RESERVED_INIT_PRIORITY - 1);
+}
+
+/* Instrument the current function.  */
+
+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);
+  return 0;
+}
+
+static bool
+gate_asan (void)
+{
+  return flag_asan != 0;
+}
+
+struct gimple_opt_pass pass_asan =
+{
+ {
+  GIMPLE_PASS,
+  "asan",                               /* name  */
+  OPTGROUP_NONE,                        /* optinfo_flags */
+  gate_asan,                            /* gate  */
+  asan_instrument,                      /* execute  */
+  NULL,                                 /* sub  */
+  NULL,                                 /* next  */
+  0,                                    /* static_pass_number  */
+  TV_NONE,                              /* tv_id  */
+  PROP_ssa | PROP_cfg | PROP_gimple_leh,/* properties_required  */
+  0,                                    /* properties_provided  */
+  0,                                    /* properties_destroyed  */
+  0,                                    /* todo_flags_start  */
+  TODO_verify_flow | TODO_verify_stmts
+  | TODO_update_ssa    /* todo_flags_finish  */
+ }
+};
diff --git a/gcc/asan.h b/gcc/asan.h
new file mode 100644
index 0000000..590cf35
--- /dev/null
+++ b/gcc/asan.h
@@ -0,0 +1,26 @@
+/* AddressSanitizer, a fast memory error detector.
+   Copyright (C) 2011 Free Software Foundation, Inc.
+   Contributed by Kostya Serebryany <kcc@google.com>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef TREE_ASAN
+#define TREE_ASAN
+
+extern void asan_finish_file(void);
+
+#endif /* TREE_ASAN */
diff --git a/gcc/common.opt b/gcc/common.opt
index 5b69aff..789f61c 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -849,6 +849,10 @@ fargument-noalias-anything
 Common Ignore
 Does nothing. Preserved for backward compatibility.
 
+faddress-sanitizer
+Common RejectNegative Report Var(flag_asan)
+Enable AddressSanitizer, a memory error detector
+
 fasynchronous-unwind-tables
 Common Report Var(flag_asynchronous_unwind_tables) Optimization
 Generate unwind tables that are exact at each instruction boundary
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index ff0c87d..16ab69a 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -353,9 +353,10 @@ Objective-C and Objective-C++ Dialects}.
 @item Optimization Options
 @xref{Optimize Options,,Options that Control Optimization}.
 @gccoptlist{-falign-functions[=@var{n}] -falign-jumps[=@var{n}] @gol
--falign-labels[=@var{n}] -falign-loops[=@var{n}] -fassociative-math @gol
--fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize @gol
--fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves @gol
+-falign-labels[=@var{n}] -falign-loops[=@var{n}] -faddress-sanitizer @gol
+--fassociative-math fauto-inc-dec -fbranch-probabilities @gol
+--fbranch-target-load-optimize fbranch-target-load-optimize2 @gol
+--fbtr-bb-exclusive -fcaller-saves @gol
 -fcheck-data-deps -fcombine-stack-adjustments -fconserve-stack @gol
 -fcompare-elim -fcprop-registers -fcrossjumping @gol
 -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules @gol
@@ -6822,6 +6823,12 @@ assumptions based on that.
 
 The default is @option{-fzero-initialized-in-bss}.
 
+@item -faddress-sanitizer
+Enable AddressSanitizer, a fast memory error detector.
+Memory access instructions will be instrumented to detect
+out-of-bounds and use-after-free bugs. So far only heap bugs will be detected.
+See @uref{http://code.google.com/p/address-sanitizer/} for more details.
+
 @item -fmudflap -fmudflapth -fmudflapir
 @opindex fmudflap
 @opindex fmudflapth
diff --git a/gcc/passes.c b/gcc/passes.c
index 67aae52..66a2f74 100644
--- a/gcc/passes.c
+++ b/gcc/passes.c
@@ -1456,6 +1456,7 @@ init_optimization_passes (void)
       NEXT_PASS (pass_split_crit_edges);
       NEXT_PASS (pass_pre);
       NEXT_PASS (pass_sink_code);
+      NEXT_PASS (pass_asan);
       NEXT_PASS (pass_tree_loop);
 	{
 	  struct opt_pass **p = &pass_tree_loop.pass.sub;
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 5cbb364..3ca0736 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -72,6 +72,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "value-prof.h"
 #include "alloc-pool.h"
 #include "tree-mudflap.h"
+#include "asan.h"
 #include "gimple.h"
 #include "tree-ssa-alias.h"
 #include "plugin.h"
@@ -570,6 +571,10 @@ compile_file (void)
       if (flag_mudflap)
 	mudflap_finish_file ();
 
+      /* File-scope initialization for AddressSanitizer.  */
+      if (flag_asan)
+        asan_finish_file ();
+
       output_shared_constant_pool ();
       output_object_blocks ();
       finish_tm_clone_pairs ();
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index 8ed2d98..73c5886 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -259,6 +259,7 @@ struct register_pass_info
 
 extern struct gimple_opt_pass pass_mudflap_1;
 extern struct gimple_opt_pass pass_mudflap_2;
+extern struct gimple_opt_pass pass_asan;
 extern struct gimple_opt_pass pass_lower_cf;
 extern struct gimple_opt_pass pass_refactor_eh;
 extern struct gimple_opt_pass pass_lower_eh;
