eliminate python SyntaxWarnings from check-all output.

```
src_dir/clang/lib/Tooling/DumpTool/generate_cxx_src_locs.py:28: SyntaxWarning: invalid escape sequence '\*'    self.implementationContent += """
src_dir/llvm/utils/lit/lit/TestRunner.py:205: SyntaxWarning: invalid escape sequence '\c'                      """
src_dir/llvm/utils/lit/lit/TestRunner.py:1561: SyntaxWarning: invalid escape sequence '\s'                     match = _caching_re_compile("^\s*%else\s*(%{)?").search(ln)
src_dir/libcxx/utils/libcxx/test/format.py:64: SyntaxWarning: invalid escape sequence '\s'                     for output in re.split('[$]\s*":"\s*"RUN: at line \d+"', fullOutput):
src_dir/libcxx/utils/libcxx/test/params.py:121: SyntaxWarning: invalid escape sequence '\+'                    AddSubstitution("%{cxx_std}", re.sub("\+", "x", std)),
src_dir/libcxx/utils/libcxx/test/params.py:214: SyntaxWarning: invalid escape sequence '\+'                    AddFeature("stdlib=libc++") if re.match(".+-libc\+\+", stdlib) else None,
src_dir/compiler-rt/test/lit.common.cfg.py:800: SyntaxWarning: invalid escape sequence '\$'                    "-Wl,-z,origin -Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec"
src_dir/compiler-rt/test/lit.common.cfg.py:809: SyntaxWarning: invalid escape sequence '\$'                    "-Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
src_dir/compiler-rt/test/lit.common.cfg.py:817: SyntaxWarning: invalid escape sequence '\$'                    "-Wl,-R\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
src_dir/llvm/test/lit.cfg.py:275: SyntaxWarning: invalid escape sequence '\d'                                  match = re.search("release (\d+)\.(\d+)", ptxas_out)
```

clang/lib/Tooling/DumpTool/generate_cxx_src_locs.py

@@ -25,7 +25,7 @@ def __init__(self, templateClasses):
 
  def GeneratePrologue(self):
 
- self.implementationContent += """
+ self.implementationContent += r"""
 /*===- Generated file -------------------------------------------*- C++ -*-===*\
 |* *|
 |* Introspection of available AST node SourceLocations *|

compiler-rt/test/lit.common.cfg.py

@@ -797,7 +797,7 @@ def is_windows_lto_supported():
  config.substitutions.append(
  (
  "%ld_flags_rpath_exe" + postfix,
- "-Wl,-z,origin -Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec"
+ r"-Wl,-z,origin -Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec"
  + postfix,
  )
  )
@@ -806,15 +806,15 @@ def is_windows_lto_supported():
  config.substitutions.append(
  (
  "%ld_flags_rpath_exe" + postfix,
- "-Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
+ r"-Wl,-rpath,\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
  )
  )
  config.substitutions.append(("%ld_flags_rpath_so" + postfix, ""))
  elif config.host_os == "SunOS":
  config.substitutions.append(
  (
  "%ld_flags_rpath_exe" + postfix,
- "-Wl,-R\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
+ r"-Wl,-R\$ORIGIN -L%T -l%xdynamiclib_namespec" + postfix,
  )
  )
  config.substitutions.append(("%ld_flags_rpath_so" + postfix, ""))

libcxx/utils/libcxx/test/format.py

@@ -61,7 +61,7 @@ def _parseLitOutput(fullOutput):
  injecting additional Lit output around it.
  """
  parsed = ''
- for output in re.split('[$]\s*":"\s*"RUN: at line \d+"', fullOutput):
+ for output in re.split(r'[$]\s*":"\s*"RUN: at line \d+"', fullOutput):
  if output: # skip blank lines
  commandOutput = re.search("# command output:\n(.+)\n$", output, flags=re.DOTALL)
  if commandOutput:

libcxx/utils/libcxx/test/params.py

@@ -118,7 +118,7 @@ def getModuleFlag(cfg, enable_modules):
  ),
  actions=lambda std: [
  AddFeature(std),
- AddSubstitution("%{cxx_std}", re.sub("\+", "x", std)),
+ AddSubstitution("%{cxx_std}", re.sub(r"\+", "x", std)),
  AddCompileFlag(lambda cfg: getStdFlag(cfg, std)),
  ],
  ),
@@ -211,7 +211,7 @@ def getModuleFlag(cfg, enable_modules):
  AddFeature("stdlib={}".format(stdlib)),
  # Also add an umbrella feature 'stdlib=libc++' for all flavors of libc++, to simplify
  # the test suite.
- AddFeature("stdlib=libc++") if re.match(".+-libc\+\+", stdlib) else None,
+ AddFeature("stdlib=libc++") if re.match(r".+-libc\+\+", stdlib) else None,
  ],
  ),
  ),

llvm/test/lit.cfg.py

@@ -272,7 +272,7 @@ def ptxas_version(ptxas):
  ptxas_cmd = subprocess.Popen([ptxas, "--version"], stdout=subprocess.PIPE)
  ptxas_out = ptxas_cmd.stdout.read().decode("ascii")
  ptxas_cmd.wait()
- match = re.search("release (\d+)\.(\d+)", ptxas_out)
+ match = re.search(r"release (\d+)\.(\d+)", ptxas_out)
  if match:
  return (int(match.group(1)), int(match.group(2)))
  print("couldn't determine ptxas version")

llvm/utils/lit/lit/TestRunner.py

@@ -202,7 +202,7 @@ def expand_glob_expressions(args, cwd):
 
 
 def quote_windows_command(seq):
- """
+ r"""
  Reimplement Python's private subprocess.list2cmdline for MSys compatibility
 
  Based on CPython implementation here:
@@ -1558,7 +1558,7 @@ def tryParseIfCond(ln):
  return cond, ln
 
  def tryParseElse(ln):
- match = _caching_re_compile("^\s*%else\s*(%{)?").search(ln)
+ match = _caching_re_compile(r"^\s*%else\s*(%{)?").search(ln)
  if not match:
  return False, ln
  if not match.group(1):