Index: clang/test/lit.cfg
===================================================================
--- clang/test/lit.cfg
+++ clang/test/lit.cfg
@@ -10,6 +10,7 @@
 import lit.util
 
 from lit.llvm import llvm_config
+from lit.llvm import ToolFilter
 
 # Configuration file for the 'lit' test runner.
 
@@ -112,55 +113,12 @@
 if config.clang_examples:
     config.available_features.add('examples')
 
-# Note that when substituting %clang_cc1 also fill in the include directory of
-# the builtin headers. Those are part of even a freestanding environment, but
-# Clang relies on the driver to locate them.
-def getClangBuiltinIncludeDir(clang):
-    # FIXME: Rather than just getting the version, we should have clang print
-    # out its resource dir here in an easy to scrape form.
-    cmd = subprocess.Popen([clang, '-print-file-name=include'],
-                           stdout=subprocess.PIPE,
-                           env=config.environment)
-    if not cmd.stdout:
-      lit_config.fatal("Couldn't find the include dir for Clang ('%s')" % clang)
-    dir = cmd.stdout.read().strip()
-    if sys.platform in ['win32'] and not llvm_config.use_lit_shell:
-        # Don't pass dosish path separator to msys bash.exe.
-        dir = dir.replace('\\', '/')
-    # Ensure the result is an ascii string, across Python2.5+ - Python3.
-    return str(dir.decode('ascii'))
-
-def makeItaniumABITriple(triple):
-    m = re.match(r'(\w+)-(\w+)-(\w+)', triple)
-    if not m:
-      lit_config.fatal("Could not turn '%s' into Itanium ABI triple" % triple)
-    if m.group(3).lower() != 'win32':
-      # All non-win32 triples use the Itanium ABI.
-      return triple
-    return m.group(1) + '-' + m.group(2) + '-mingw32'
-
-def makeMSABITriple(triple):
-    m = re.match(r'(\w+)-(\w+)-(\w+)', triple)
-    if not m:
-      lit_config.fatal("Could not turn '%s' into MS ABI triple" % triple)
-    isa = m.group(1).lower()
-    vendor = m.group(2).lower()
-    os = m.group(3).lower()
-    if os == 'win32':
-      # If the OS is win32, we're done.
-      return triple
-    if isa.startswith('x86') or isa == 'amd64' or re.match(r'i\d86', isa):
-      # For x86 ISAs, adjust the OS.
-      return isa + '-' + vendor + '-win32'
-    # -win32 is not supported for non-x86 targets; use a default.
-    return 'i686-pc-win32'
-
+builtin_include_dir = llvm_config.get_clang_builtin_include_dir(config.clang)
 config.substitutions.append( ('%clang_analyze_cc1',
                               '%clang_cc1 -analyze %analyze') )
 config.substitutions.append( ('%clang_cc1',
                               '%s -cc1 -internal-isystem %s -nostdsysteminc'
-                              % (config.clang,
-                                 getClangBuiltinIncludeDir(config.clang))) )
+                              % (config.clang, builtin_include_dir)) )
 config.substitutions.append( ('%clang_cpp', ' ' + config.clang +
                               ' --driver-mode=cpp '))
 config.substitutions.append( ('%clang_cl', ' ' + config.clang +
@@ -168,16 +126,20 @@
 config.substitutions.append( ('%clangxx', ' ' + config.clang +
                               ' --driver-mode=g++ '))
 config.substitutions.append( ('%clang', ' ' + config.clang + ' ') )
-config.substitutions.append( ('%test_debuginfo', ' ' + config.llvm_src_root + '/utils/test_debuginfo.pl ') )
-config.substitutions.append( ('%itanium_abi_triple', makeItaniumABITriple(config.target_triple)) )
-config.substitutions.append( ('%ms_abi_triple', makeMSABITriple(config.target_triple)) )
-config.substitutions.append( ('%resource_dir', getClangBuiltinIncludeDir(config.clang)) )
+config.substitutions.append( ('%test_debuginfo',
+                             ' ' + config.llvm_src_root +  '/utils/test_debuginfo.pl ') )
+config.substitutions.append( ('%itanium_abi_triple',
+                             llvm_config.make_itanium_abi_triple(config.target_triple)) )
+config.substitutions.append( ('%ms_abi_triple',
+                             llvm_config.make_msabi_triple(config.target_triple)) )
+config.substitutions.append( ('%resource_dir', builtin_include_dir) )
 config.substitutions.append( ('%python', config.python_executable) )
 
 # The host triple might not be set, at least if we're compiling clang from
 # an already installed llvm.
 if config.host_triple and config.host_triple != '@LLVM_HOST_TRIPLE@':
-    config.substitutions.append( ('%target_itanium_abi_host_triple', '--target=%s' % makeItaniumABITriple(config.host_triple)) )
+    config.substitutions.append( ('%target_itanium_abi_host_triple',
+                                 '--target=%s' % llvm_config.make_itanium_abi_triple(config.host_triple)) )
 else:
     config.substitutions.append( ('%target_itanium_abi_host_triple', '') )
 
@@ -207,50 +169,27 @@
     (' %clang-cl ',
      """*** invalid substitution, use '%clang_cl'. ***""") )
 
-# For each occurrence of a clang tool name as its own word, replace it
-# with the full path to the build directory holding that tool.  This
-# ensures that we are testing the tools just built and not some random
+# For each occurrence of a clang tool name, replace it with the full path to
+# the build directory holding that tool.  We explicitly specify the directories
+# to search to ensure that we get the tools just built and not some random
 # tools that might happen to be in the user's PATH.
-tool_dirs = os.path.pathsep.join((config.clang_tools_dir, config.llvm_tools_dir))
-
-# Regex assertions to reject neighbor hyphens/dots (seen in some tests).
-# For example, don't match 'clang-check-' or '.clang-format'.
-NoPreHyphenDot = r"(?<!(-|\.))"
-NoPostHyphenDot = r"(?!(-|\.))"
-NoPostBar = r"(?!(/|\\))"
-
-tool_patterns = [r"\bFileCheck\b",
-                 r"\bc-index-test\b",
-                 NoPreHyphenDot + r"\bclang-check\b" + NoPostHyphenDot,
-                 NoPreHyphenDot + r"\bclang-diff\b" + NoPostHyphenDot,
-                 NoPreHyphenDot + r"\bclang-format\b" + NoPostHyphenDot,
-                 # FIXME: Some clang test uses opt?
-                 NoPreHyphenDot + r"\bopt\b" + NoPostBar + NoPostHyphenDot,
-                 # Handle these specially as they are strings searched
-                 # for during testing.
-                 r"\| \bcount\b",
-                 r"\| \bnot\b"]
+tool_dirs = [config.clang_tools_dir, config.llvm_tools_dir]
+
+tool_patterns = [
+    'FileCheck', 'c-index-test',
+    ToolFilter('clang-check', '-.', '-.'),
+    ToolFilter('clang-diff', '-.', '-.'),
+    ToolFilter('clang-format', '-.', '-.'),
+    # FIXME: Some clang test uses opt?
+    ToolFilter('opt', '-.', r'/\-.'),
+    # Handle these specially as they are strings searched for during testing.
+    ToolFilter('count', '\ '),
+    ToolFilter('not', '\ ')]
 
 if config.clang_examples:
-    tool_patterns.append(NoPreHyphenDot + r"\bclang-interpreter\b" + NoPostHyphenDot)
-
-for pattern in tool_patterns:
-    # Extract the tool name from the pattern.  This relies on the tool
-    # name being surrounded by \b word match operators.  If the
-    # pattern starts with "| ", include it in the string to be
-    # substituted.
-    tool_match = re.match(r"^(\\)?((\| )?)\W+b([0-9A-Za-z-_]+)\\b\W*$",
-                          pattern)
-    tool_pipe = tool_match.group(2)
-    tool_name = tool_match.group(4)
-    tool_path = lit.util.which(tool_name, tool_dirs)
-    if not tool_path:
-        # Warn, but still provide a substitution.
-        lit_config.note('Did not find ' + tool_name + ' in ' + tool_dirs)
-        tool_path = config.clang_tools_dir + '/' + tool_name
-    config.substitutions.append((pattern, tool_pipe + tool_path))
-
-###
+    tool_patterns.append(ToolFilter('clang-interpreter', '-.', '-.'))
+
+llvm_config.add_tool_substitutions(tool_patterns, tool_dirs)
 
 # Set available features we allow tests to conditionalize on.
 #
Index: lld/test/CMakeLists.txt
===================================================================
--- lld/test/CMakeLists.txt
+++ lld/test/CMakeLists.txt
@@ -17,8 +17,11 @@
   HAVE_LIBZ)
 
 configure_lit_site_cfg(
-  ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
-  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg)
+  ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
+  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py
+  MAIN_CONFIG
+  ${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg.py
+  )
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.in
   ${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg
Index: lld/test/lit.cfg.py
===================================================================
--- lld/test/lit.cfg.py
+++ lld/test/lit.cfg.py
@@ -10,6 +10,7 @@
 import lit.util
 
 from lit.llvm import llvm_config
+from lit.llvm import ToolFilter
 
 # Configuration file for the 'lit' test runner.
 
@@ -36,58 +37,30 @@
 config.test_exec_root = os.path.join(config.lld_obj_root, 'test')
 
 # Tweak the PATH to include the tools dir and the scripts dir.
-llvm_config.with_environment('PATH', [config.llvm_tools_dir, config.lld_tools_dir], append_path=True)
+llvm_config.with_environment('PATH',
+                             [config.llvm_tools_dir, config.lld_tools_dir], append_path=True)
 
-llvm_config.with_environment('LD_LIBRARY_PATH', [config.lld_libs_dir, config.llvm_libs_dir], append_path=True)
+llvm_config.with_environment('LD_LIBRARY_PATH',
+                             [config.lld_libs_dir, config.llvm_libs_dir], append_path=True)
 
-# For each occurrence of a lld tool name as its own word, replace it
-# with the full path to the build directory holding that tool.  This
-# ensures that we are testing the tools just built and not some random
+# For each occurrence of a clang tool name, replace it with the full path to
+# the build directory holding that tool.  We explicitly specify the directories
+# to search to ensure that we get the tools just built and not some random
 # tools that might happen to be in the user's PATH.
-
-# Regex assertions to reject neighbor hyphens/dots (seen in some tests).
-# For example, we want to prefix 'lld' and 'ld.lld' but not the 'lld' inside
-# of 'ld.lld'.
-NoPreJunk = r"(?<!(-|\.|/))"
-NoPostJunk = r"(?!(-|\.))"
+tool_dirs = [config.lld_tools_dir, config.llvm_tools_dir]
 
 config.substitutions.append( (r"\bld.lld\b", 'ld.lld --full-shutdown') )
 
-tool_patterns = [r"\bFileCheck\b",
-                 r"\bnot\b",
-                 NoPreJunk + r"\blld\b" + NoPostJunk,
-                 r"\bld.lld\b",
-                 r"\blld-link\b",
-                 r"\bllvm-as\b",
-                 r"\bllvm-mc\b",
-                 r"\bllvm-nm\b",
-                 r"\bllvm-objdump\b",
-                 r"\bllvm-pdbutil\b",
-                 r"\bllvm-readobj\b",
-                 r"\bobj2yaml\b",
-                 r"\byaml2obj\b"]
-
-for pattern in tool_patterns:
-    # Extract the tool name from the pattern.  This relies on the tool
-    # name being surrounded by \b word match operators.  If the
-    # pattern starts with "| ", include it in the string to be
-    # substituted.
-    tool_match = re.match(r"^(\\)?((\| )?)\W+b([0-9A-Za-z-_\.]+)\\b\W*$",
-                          pattern)
-    tool_pipe = tool_match.group(2)
-    tool_name = tool_match.group(4)
-    tool_path = lit.util.which(tool_name, config.environment['PATH'])
-    if not tool_path:
-        # Warn, but still provide a substitution.
-        lit_config.note('Did not find ' + tool_name + ' in ' + path)
-        tool_path = config.llvm_tools_dir + '/' + tool_name
-    config.substitutions.append((pattern, tool_pipe + tool_path))
+tool_patterns = [
+    'FileCheck', 'not', 'ld.lld', 'lld-link', 'llvm-as', 'llvm-mc', 'llvm-nm',
+    'llvm-objdump', 'llvm-pdbutil', 'llvm-readobj', 'obj2yaml', 'yaml2obj',
+    ToolFilter('lld', '-.', '-.')]
+
+llvm_config.add_tool_substitutions(tool_patterns, tool_dirs)
 
 # Add site-specific substitutions.
 config.substitutions.append( ('%python', config.python_executable) )
 
-###
-
 # When running under valgrind, we mangle '-vg' onto the end of the triple so we
 # can check it with XFAIL and XTARGET.
 if lit_config.useValgrind:
Index: lld/test/lit.site.cfg.py.in
===================================================================
--- lld/test/lit.site.cfg.py.in
+++ lld/test/lit.site.cfg.py.in
@@ -25,4 +25,4 @@
 @LIT_SITE_CFG_IN_FOOTER@
 
 # Let the main config do the real work.
-lit_config.load_config(config, "@LLD_SOURCE_DIR@/test/lit.cfg")
+lit_config.load_config(config, "@LLD_SOURCE_DIR@/test/lit.cfg.py")
Index: llvm/test/lit.cfg.py
===================================================================
--- llvm/test/lit.cfg.py
+++ llvm/test/lit.cfg.py
@@ -11,6 +11,7 @@
 import lit.util
 import lit.formats
 from lit.llvm import llvm_config
+from lit.llvm import ToolFilter
 
 # name: The name of this test suite.
 config.name = 'LLVM'
@@ -134,108 +135,39 @@
 # The regex is a pre-assertion to avoid matching a preceding
 # dot, hyphen, carat, or slash (.foo, -foo, etc.).  Some patterns
 # also have a post-assertion to not match a trailing hyphen (foo-).
-NOJUNK = r"(?<!\.|-|\^|/|<)"
-
-
-def find_tool_substitution(pattern):
-    # Extract the tool name from the pattern.  This relies on the tool
-    # name being surrounded by \b word match operators.  If the
-    # pattern starts with "| ", include it in the string to be
-    # substituted.
-    tool_match = re.match(r"^(\\)?((\| )?)\W+b([0-9A-Za-z-_]+)\\b\W*$",
-                          pattern)
-    tool_pipe = tool_match.group(2)
-    tool_name = tool_match.group(4)
-    # Did the user specify the tool path + arguments? This allows things like
-    # llvm-lit "-Dllc=llc -enable-misched -verify-machineinstrs"
-    tool_path = lit_config.params.get(tool_name)
-    if tool_path is None:
-        tool_path = lit.util.which(tool_name, config.llvm_tools_dir)
-        if tool_path is None:
-            return tool_name, tool_path, tool_pipe
-    if (tool_name == "llc" and
-       'LLVM_ENABLE_MACHINE_VERIFIER' in os.environ and
-       os.environ['LLVM_ENABLE_MACHINE_VERIFIER'] == "1"):
-        tool_path += " -verify-machineinstrs"
-    if (tool_name == "llvm-go"):
-        tool_path += " go=" + config.go_executable
-    return tool_name, tool_path, tool_pipe
-
-
-for pattern in [r"\bbugpoint\b(?!-)",
-                NOJUNK + r"\bllc\b",
-                r"\blli\b",
-                r"\bllvm-ar\b",
-                r"\bllvm-as\b",
-                r"\bllvm-bcanalyzer\b",
-                r"\bllvm-config\b",
-                r"\bllvm-cov\b",
-                r"\bllvm-cxxdump\b",
-                r"\bllvm-cvtres\b",
-                r"\bllvm-diff\b",
-                r"\bllvm-dis\b",
-                r"\bllvm-dsymutil\b",
-                r"\bllvm-dwarfdump\b",
-                r"\bllvm-extract\b",
-                r"\bllvm-isel-fuzzer\b",
-                r"\bllvm-lib\b",
-                r"\bllvm-link\b",
-                r"\bllvm-lto\b",
-                r"\bllvm-lto2\b",
-                r"\bllvm-mc\b",
-                r"\bllvm-mcmarkup\b",
-                r"\bllvm-modextract\b",
-                r"\bllvm-nm\b",
-                r"\bllvm-objcopy\b",
-                r"\bllvm-objdump\b",
-                r"\bllvm-pdbutil\b",
-                r"\bllvm-profdata\b",
-                r"\bllvm-ranlib\b",
-                r"\bllvm-readobj\b",
-                r"\bllvm-rtdyld\b",
-                r"\bllvm-size\b",
-                r"\bllvm-split\b",
-                r"\bllvm-strings\b",
-                r"\bllvm-tblgen\b",
-                r"\bllvm-c-test\b",
-                r"\bllvm-cxxfilt\b",
-                r"\bllvm-xray\b",
-                NOJUNK + r"\bllvm-symbolizer\b",
-                NOJUNK + r"\bopt\b",
-                r"\bFileCheck\b",
-                r"\bobj2yaml\b",
-                NOJUNK + r"\bsancov\b",
-                NOJUNK + r"\bsanstats\b",
-                r"\byaml2obj\b",
-                r"\byaml-bench\b",
-                r"\bverify-uselistorder\b",
-                # Handle these specially as they are strings searched
-                # for during testing.
-                r"\| \bcount\b",
-                r"\| \bnot\b"]:
-    tool_name, tool_path, tool_pipe = find_tool_substitution(pattern)
-    if not tool_path:
-        # Warn, but still provide a substitution.
-        lit_config.note('Did not find ' + tool_name + ' in ' + config.llvm_tools_dir)
-        tool_path = config.llvm_tools_dir + '/' + tool_name
-    config.substitutions.append((pattern, tool_pipe + tool_path))
+JUNKCHARS = r".-^/<"
+
+required_tools = [
+    'lli', 'llvm-ar', 'llvm-as', 'llvm-bcanalyzer', 'llvm-config', 'llvm-cov',
+    'llvm-cxxdump', 'llvm-cvtres', 'llvm-diff', 'llvm-dis', 'llvm-dsymutil',
+    'llvm-dwarfdump', 'llvm-extract', 'llvm-isel-fuzzer', 'llvm-lib',
+    'llvm-link', 'llvm-lto', 'llvm-lto2', 'llvm-mc', 'llvm-mcmarkup',
+    'llvm-modextract', 'llvm-nm', 'llvm-objcopy', 'llvm-objdump',
+    'llvm-pdbutil', 'llvm-profdata', 'llvm-ranlib', 'llvm-readobj',
+    'llvm-rtdyld', 'llvm-size', 'llvm-split', 'llvm-strings', 'llvm-tblgen',
+    'llvm-c-test', 'llvm-cxxfilt', 'llvm-xray', 'yaml2obj', 'obj2yaml',
+    'FileCheck', 'yaml-bench', 'verify-uselistorder',
+    ToolFilter('bugpoint', post='-'),
+    ToolFilter('llc', pre=JUNKCHARS),
+    ToolFilter('llvm-symbolizer', pre=JUNKCHARS),
+    ToolFilter('opt', JUNKCHARS),
+    ToolFilter('sancov', pre=JUNKCHARS),
+    ToolFilter('sanstats', pre=JUNKCHARS),
+    # Handle these specially as they are strings searched for during testing.
+    ToolFilter(r'\| \bcount\b', literal=True),
+    ToolFilter(r'\| \bnot\b', literal=True)]
+
+llvm_config.add_tool_substitutions(required_tools, config.llvm_tools_dir)
 
 # For tools that are optional depending on the config, we won't warn
 # if they're missing.
-for pattern in [r"\bllvm-go\b",
-                r"\bllvm-mt\b",
-                r"\bKaleidoscope-Ch3\b",
-                r"\bKaleidoscope-Ch4\b",
-                r"\bKaleidoscope-Ch5\b",
-                r"\bKaleidoscope-Ch6\b",
-                r"\bKaleidoscope-Ch7\b",
-                r"\bKaleidoscope-Ch8\b"]:
-    tool_name, tool_path, tool_pipe = find_tool_substitution(pattern)
-    if not tool_path:
-        # Provide a substitution anyway, for the sake of consistent errors.
-        tool_path = config.llvm_tools_dir + '/' + tool_name
-    config.substitutions.append((pattern, tool_pipe + tool_path))
 
+optional_tools = [
+    'llvm-go', 'llvm-mt', 'Kaleidoscope-Ch3', 'Kaleidoscope-Ch4',
+    'Kaleidoscope-Ch5', 'Kaleidoscope-Ch6', 'Kaleidoscope-Ch7',
+    'Kaleidoscope-Ch8']
+llvm_config.add_tool_substitutions(optional_tools, config.llvm_tools_dir,
+                                   warn_missing=False)
 
 ### Targets
 
Index: llvm/utils/lit/lit/llvm/__init__.py
===================================================================
--- llvm/utils/lit/lit/llvm/__init__.py
+++ llvm/utils/lit/lit/llvm/__init__.py
@@ -1,9 +1,60 @@
-
 from lit.llvm import config
+import lit.util
 
 llvm_config = None
 
+class ToolFilter(object):
+    """
+        String-like class used to build regex substitution patterns for
+        llvm tools.  Handles things like adding word-boundary patterns,
+        and filtering characters from the beginning an end of a tool name
+    """
+
+    def __init__(self, name, pre=None, post=None, literal=False):
+        """
+            Construct a ToolFilter.
+
+            name: the literal name of the substitution to look for.
+
+            pre: If specified, the substitution will not find matches where
+            the character immediately preceding the word-boundary that begins
+            `name` is any of the characters in the string `pre`.
+
+            post: If specified, the substitution will not find matches where
+            the character immediately after the word-boundary that ends `name`
+            is any of the characters specified in the string `post`.
+
+            literal: If True, `name` is an exact regex that is passed to the
+            underlying substitution
+        """
+        def any_char_in(chars):
+            def escape_one(c):
+                if c in r'\^$[.:|?*':
+                    return '\\' + c
+                return c
+            return '|'.join([escape_one(x) for x in chars])
+
+        if literal:
+            self.regex = name
+            return
+
+        name = lit.util.make_word_regex(name)
+        if pre and len(pre) > 0:
+            pre = any_char_in(pre)
+            regex = '(?<!(%s))' % pre
+            name = regex + name
+        if post and len(post) > 0:
+            post = any_char_in(post)
+            regex = '(?!(%s))' % post
+            name = name + regex
+        self.regex = name
+
+    def __str__(self):
+        return self.regex
+
+
 def initialize(lit_config, test_config):
     global llvm_config
+
     llvm_config = config.LLVMConfig(lit_config, test_config)
 
Index: llvm/utils/lit/lit/llvm/config.py
===================================================================
--- llvm/utils/lit/lit/llvm/config.py
+++ llvm/utils/lit/lit/llvm/config.py
@@ -132,22 +132,26 @@
             if name in self.config.environment:
                 del self.config.environment[name]
 
+    def get_process_output(self, command, encoding='ascii'):
+        try:
+            cmd = subprocess.Popen(
+                command, stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE, env=self.config.environment)
+            stdout, stderr = cmd.communicate()
+            stdout = stdout.decode(encoding)
+            stderr = stderr.decode(encoding)
+            return (stdout, stderr)
+        except OSError:
+            self.lit_config.fatal("Could not run process %s" % command)
+
     def feature_config(self, features, encoding = 'ascii'):
         # Ask llvm-config about the specified feature.
         arguments = [x for (x, _) in features]
-        try:
-            config_path = os.path.join(self.config.llvm_tools_dir, 'llvm-config')
-
-            llvm_config_cmd = subprocess.Popen(
-                [config_path] + arguments,
-                stdout = subprocess.PIPE,
-                env=self.config.environment)
-        except OSError:
-            self.lit_config.fatal("Could not find llvm-config in " + self.config.llvm_tools_dir)
+        config_path = os.path.join(self.config.llvm_tools_dir, 'llvm-config')
 
-        output, _ = llvm_config_cmd.communicate()
-        output = output.decode(encoding)
+        output, _ = self.get_process_output([config_path] + arguments, encoding)
         lines = output.split('\n')
+
         for (line, (_, patterns)) in zip(lines, features):
             # We should have either a callable or a dictionary.  If it's a
             # dictionary, grep each key against the output and use the value if
@@ -159,3 +163,84 @@
                 for (match, feature) in patterns.items():
                     if re.search(line, match):
                         self.config.available_features.add(feature)
+
+
+    # Note that when substituting %clang_cc1 also fill in the include directory of
+    # the builtin headers. Those are part of even a freestanding environment, but
+    # Clang relies on the driver to locate them.
+    def get_clang_builtin_include_dir(self, clang):
+        # FIXME: Rather than just getting the version, we should have clang print
+        # out its resource dir here in an easy to scrape form.
+        dir, _ = self.get_process_output([clang, '-print-file-name=include'], encoding='ascii')
+
+        if not dir:
+          self.lit_config.fatal("Couldn't find the include dir for Clang ('%s')" % clang)
+
+        dir = dir.strip()
+        if sys.platform in ['win32'] and not self.use_lit_shell:
+            # Don't pass dosish path separator to msys bash.exe.
+            dir = dir.replace('\\', '/')
+        # Ensure the result is an ascii string, across Python2.5+ - Python3.
+        return dir
+
+    def make_itanium_abi_triple(self, triple):
+        m = re.match(r'(\w+)-(\w+)-(\w+)', triple)
+        if not m:
+          self.lit_config.fatal("Could not turn '%s' into Itanium ABI triple" % triple)
+        if m.group(3).lower() != 'win32':
+          # All non-win32 triples use the Itanium ABI.
+          return triple
+        return m.group(1) + '-' + m.group(2) + '-mingw32'
+
+    def make_msabi_triple(self, triple):
+        m = re.match(r'(\w+)-(\w+)-(\w+)', triple)
+        if not m:
+          self.lit_config.fatal("Could not turn '%s' into MS ABI triple" % triple)
+        isa = m.group(1).lower()
+        vendor = m.group(2).lower()
+        os = m.group(3).lower()
+        if os == 'win32':
+          # If the OS is win32, we're done.
+          return triple
+        if isa.startswith('x86') or isa == 'amd64' or re.match(r'i\d86', isa):
+          # For x86 ISAs, adjust the OS.
+          return isa + '-' + vendor + '-win32'
+        # -win32 is not supported for non-x86 targets; use a default.
+        return 'i686-pc-win32'
+
+    def add_tool_substitutions(self, tools, search_dirs, warn_missing = True):
+        if isinstance(search_dirs, basestring):
+            search_dirs = [search_dirs]
+        search_dirs = os.pathsep.join(search_dirs)
+        for tool in tools:
+            # Extract the tool name from the pattern.  This relies on the tool
+            # name being surrounded by \b word match operators.  If the
+            # pattern starts with "| ", include it in the string to be
+            # substituted.
+            if isinstance(tool, basestring):
+                tool = lit.util.make_word_regex(tool)
+            else:
+                tool = str(tool)
+
+            tool_match = re.match(r"^(\\)?((\| )?)\W+b([0-9A-Za-z-_]+)\\b\W*$",
+                                  tool)
+            if not tool_match:
+                continue
+
+            tool_pipe = tool_match.group(2)
+            tool_name = tool_match.group(4)
+            tool_path = lit.util.which(tool_name, search_dirs)
+            if not tool_path:
+                if warn_missing:
+                    # Warn, but still provide a substitution.
+                    self.lit_config.note('Did not find ' + tool_name + ' in %s' % search_dirs)
+                tool_path = self.config.llvm_tools_dir + '/' + tool_name
+
+            if tool_name == 'llc' and os.environ.get('LLVM_ENABLE_MACHINE_VERIFIER') == '1':
+                tool_path += ' -verify-machineinstrs'
+            if tool_name == 'llvm-go':
+                exe = getattr(self.config, 'go_executable', None)
+                if exe:
+                    tool_path += " go=" + exe
+
+            self.config.substitutions.append((tool, tool_pipe + tool_path))
Index: llvm/utils/lit/lit/util.py
===================================================================
--- llvm/utils/lit/lit/util.py
+++ llvm/utils/lit/lit/util.py
@@ -23,6 +23,8 @@
             return False
     raise ValueError('"{}" is not a valid boolean'.format(value))
 
+def make_word_regex(word):
+    return r'\b' + word + r'\b'
 
 def to_bytes(s):
     """Return the parameter as type 'bytes', possibly encoding it.