[Support] extend llvm:Regex::sub() for global substitution

[danix800]

Summary

Extend llvm::Regex::sub() to do global substitution.

llvm/include/llvm/Support/Regex.h

     /// backreferences, trailing backslashes) will be recorded as a non-empty
     /// string. If there is no error, it will be an empty string.
     std::string sub(StringRef Repl, StringRef String,
-                    std::string *Error = nullptr) const;
+                    std::string *Error = nullptr, bool Global = false) const;
 
     /// If this function returns true, ^Str$ is an extended regular
     /// expression that matches Str and only Str.

llvm/lib/Support/Regex.cpp

 }
 
 std::string Regex::sub(StringRef Repl, StringRef String,
-                       std::string *Error) const {
+                       std::string *Error, bool Global) const {
   SmallVector<StringRef, 8> Matches;
 
   // Return the input if there was no match.

   // Otherwise splice in the replacement string, starting with the prefix before
   // the match.
   std::string Res(String.begin(), Matches[0].begin());
+  StringRef OrigRepl = Repl;
 
   // Then the replacement string, honoring possible substitutions.
   while (!Repl.empty()) {

     }
   }
 
+  StringRef Suffix(Matches[0].end(), String.end() - Matches[0].end());
   // And finally the suffix.
-  Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
+  Res += (Global ? sub(OrigRepl, Suffix, Error, Global) : Suffix);
 
   return Res;
 }

llvm/unittests/Support/RegexTest.cpp

 
   EXPECT_EQ("aber", Regex("a[0-9]+b").sub("a\\100b", "a1234ber", &Error));
   EXPECT_EQ(Error, "invalid backreference string '100'");
+
+  // Global substitution
+  EXPECT_EQ("a%%b%%c%%d", Regex("%").sub("%%", "a%b%c%d", nullptr, true));
 }
 
 TEST_F(RegexTest, IsLiteralERE) {