Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
@@ -224,6 +224,13 @@
 bool RenameFile(const char *oldpath, const char *newpath,
                 error_t *error_p = nullptr);
 
+// Scoped file handle closer.
+struct FileCloser {
+  explicit FileCloser(fd_t fd) : fd(fd) {}
+  ~FileCloser() { CloseFile(fd); }
+  fd_t fd;
+};
+
 bool SupportsColoredOutput(fd_t fd);
 
 // Opens the file 'file_name" and reads up to 'max_len' bytes.
Index: compiler-rt/trunk/lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_win.cc
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_win.cc
@@ -323,6 +323,58 @@
   internal__exit(3);
 }
 
+// Read the file to extract the ImageBase field from the PE header. If ASLR is
+// disabled and this virtual address is available, the loader will typically
+// load the image at this address. Therefore, we call it the preferred base. Any
+// addresses in the DWARF typically assume that the object has been loaded at
+// this address.
+static uptr GetPreferredBase(const char *modname) {
+  fd_t fd = OpenFile(modname, RdOnly, nullptr);
+  if (fd == kInvalidFd)
+    return 0;
+  FileCloser closer(fd);
+
+  // Read just the DOS header.
+  IMAGE_DOS_HEADER dos_header;
+  uptr bytes_read;
+  if (!ReadFromFile(fd, &dos_header, sizeof(dos_header), &bytes_read) ||
+      bytes_read != sizeof(dos_header))
+    return 0;
+
+  // The file should start with the right signature.
+  if (dos_header.e_magic != IMAGE_DOS_SIGNATURE)
+    return 0;
+
+  // The layout at e_lfanew is:
+  // "PE\0\0"
+  // IMAGE_FILE_HEADER
+  // IMAGE_OPTIONAL_HEADER
+  // Seek to e_lfanew and read all that data.
+  char buf[4 + sizeof(IMAGE_FILE_HEADER) + sizeof(IMAGE_OPTIONAL_HEADER)];
+  if (::SetFilePointer(fd, dos_header.e_lfanew, nullptr, FILE_BEGIN) ==
+      INVALID_SET_FILE_POINTER)
+    return 0;
+  if (!ReadFromFile(fd, &buf[0], sizeof(buf), &bytes_read) ||
+      bytes_read != sizeof(buf))
+    return 0;
+
+  // Check for "PE\0\0" before the PE header.
+  char *pe_sig = &buf[0];
+  if (internal_memcmp(pe_sig, "PE\0\0", 4) != 0)
+    return 0;
+
+  // Skip over IMAGE_FILE_HEADER. We could do more validation here if we wanted.
+  IMAGE_OPTIONAL_HEADER *pe_header =
+      (IMAGE_OPTIONAL_HEADER *)(pe_sig + 4 + sizeof(IMAGE_FILE_HEADER));
+
+  // Check for more magic in the PE header.
+  if (pe_header->Magic != IMAGE_NT_OPTIONAL_HDR_MAGIC)
+    return 0;
+
+  // Finally, return the ImageBase.
+  return (uptr)pe_header->ImageBase;
+}
+
 uptr GetListOfModules(LoadedModule *modules, uptr max_modules,
                       string_predicate_t filter) {
   HANDLE cur_process = GetCurrentProcess();
@@ -355,19 +407,33 @@
     if (!GetModuleInformation(cur_process, handle, &mi, sizeof(mi)))
       continue;
 
-    char module_name[MAX_PATH];
-    bool got_module_name =
-        GetModuleFileNameA(handle, module_name, sizeof(module_name));
-    if (!got_module_name)
-      module_name[0] = '\0';
+    // Get the UTF-16 path and convert to UTF-8.
+    wchar_t modname_utf16[kMaxPathLength];
+    int modname_utf16_len =
+        GetModuleFileNameW(handle, modname_utf16, kMaxPathLength);
+    if (modname_utf16_len == 0)
+      modname_utf16[0] = '\0';
+    char module_name[kMaxPathLength];
+    int module_name_len =
+        ::WideCharToMultiByte(CP_UTF8, 0, modname_utf16, modname_utf16_len + 1,
+                              &module_name[0], kMaxPathLength, NULL, NULL);
+    module_name[module_name_len] = '\0';
 
     if (filter && !filter(module_name))
       continue;
 
     uptr base_address = (uptr)mi.lpBaseOfDll;
     uptr end_address = (uptr)mi.lpBaseOfDll + mi.SizeOfImage;
+
+    // Adjust the base address of the module so that we get a VA instead of an
+    // RVA when computing the module offset. This helps llvm-symbolizer find the
+    // right DWARF CU. In the common case that the image is loaded at it's
+    // preferred address, we will now print normal virtual addresses.
+    uptr preferred_base = GetPreferredBase(&module_name[0]);
+    uptr adjusted_base = base_address - preferred_base;
+
     LoadedModule *cur_module = &modules[count];
-    cur_module->set(module_name, base_address);
+    cur_module->set(module_name, adjusted_base);
     // We add the whole module as one single address range.
     cur_module->addAddressRange(base_address, end_address, /*executable*/ true);
     count++;
@@ -402,10 +468,17 @@
 
 // ------------------ sanitizer_libc.h
 fd_t OpenFile(const char *filename, FileAccessMode mode, error_t *last_error) {
-  if (mode != WrOnly)
+  fd_t res;
+  if (mode == RdOnly) {
+    res = CreateFile(filename, GENERIC_READ,
+                     FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                     nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+  } else if (mode == WrOnly) {
+    res = CreateFile(filename, GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS,
+                     FILE_ATTRIBUTE_NORMAL, nullptr);
+  } else {
     UNIMPLEMENTED();
-  fd_t res = CreateFile(filename, GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS,
-                        FILE_ATTRIBUTE_NORMAL, nullptr);
+  }
   CHECK(res != kStdoutFd || kStdoutFd == kInvalidFd);
   CHECK(res != kStderrFd || kStderrFd == kInvalidFd);
   if (res == kInvalidFd && last_error)
@@ -419,7 +492,11 @@
 
 bool ReadFromFile(fd_t fd, void *buff, uptr buff_size, uptr *bytes_read,
                   error_t *error_p) {
-  UNIMPLEMENTED();
+  CHECK(fd != kInvalidFd);
+  bool success = ::ReadFile(fd, buff, buff_size, bytes_read, nullptr);
+  if (!success && error_p)
+    *error_p = GetLastError();
+  return success;
 }
 
 bool SupportsColoredOutput(fd_t fd) {
Index: compiler-rt/trunk/test/asan/TestCases/Windows/unsymbolized.cc
===================================================================
--- compiler-rt/trunk/test/asan/TestCases/Windows/unsymbolized.cc
+++ compiler-rt/trunk/test/asan/TestCases/Windows/unsymbolized.cc
@@ -0,0 +1,25 @@
+// When we link a binary without the -debug flag, ASan should print out VAs
+// instead of RVAs. The frames for main and do_uaf should be above 0x400000,
+// which is the default image base of an executable.
+
+// RUN: rm -f %t.pdb
+// RUN: %clangxx_asan -c -O2 %s -o %t.obj
+// RUN: link /nologo /OUT:%t.exe %t.obj %asan_lib %asan_cxx_lib
+// RUN: not %run %t.exe 2>&1 | FileCheck %s
+
+#include <stdlib.h>
+#include <stdio.h>
+int __attribute__((noinline)) do_uaf(void);
+int main() {
+  int r = do_uaf();
+  printf("r: %d\n", r);
+  return r;
+}
+int do_uaf(void) {
+  char *x = (char*)malloc(10 * sizeof(char));
+  free(x);
+  return x[5];
+  // CHECK: AddressSanitizer: heap-use-after-free
+  // CHECK: #0 {{0x[a-f0-9]+ \(.*[\\/]unsymbolized.cc.*.exe\+0x40[a-f0-9]{4}\)}}
+  // CHECK: #1 {{0x[a-f0-9]+ \(.*[\\/]unsymbolized.cc.*.exe\+0x40[a-f0-9]{4}\)}}
+}
Index: compiler-rt/trunk/test/asan/lit.cfg
===================================================================
--- compiler-rt/trunk/test/asan/lit.cfg
+++ compiler-rt/trunk/test/asan/lit.cfg
@@ -113,8 +113,10 @@
   clang_invocation = build_invocation(clang_cl_asan_cxxflags)
   clang_cl_invocation = clang_invocation.replace("clang.exe","clang-cl.exe")
   config.substitutions.append( ("%clang_cl_asan ", clang_cl_invocation) )
-  config.substitutions.append( ("%asan_dll_thunk",
-                               os.path.join(config.compiler_rt_libdir, "clang_rt.asan_dll_thunk-i386.lib")))
+  base_lib = os.path.join(config.compiler_rt_libdir, "clang_rt.asan%%s-%s.lib" % config.target_arch)
+  config.substitutions.append( ("%asan_lib", base_lib % "") )
+  config.substitutions.append( ("%asan_cxx_lib", base_lib % "_cxx") )
+  config.substitutions.append( ("%asan_dll_thunk", base_lib % "_dll_thunk") )
 
 # FIXME: De-hardcode this path.
 asan_source_dir = os.path.join(