diff --git a/llvm/include/llvm/Support/Regex.h b/llvm/include/llvm/Support/Regex.h
--- a/llvm/include/llvm/Support/Regex.h
+++ b/llvm/include/llvm/Support/Regex.h
@@ -95,7 +95,7 @@
     /// 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.
diff --git a/llvm/lib/Support/Regex.cpp b/llvm/lib/Support/Regex.cpp
--- a/llvm/lib/Support/Regex.cpp
+++ b/llvm/lib/Support/Regex.cpp
@@ -131,7 +131,7 @@
 }
 
 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.
@@ -141,6 +141,7 @@
   // 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()) {
@@ -197,8 +198,9 @@
     }
   }
 
+  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;
 }
diff --git a/llvm/unittests/Support/RegexTest.cpp b/llvm/unittests/Support/RegexTest.cpp
--- a/llvm/unittests/Support/RegexTest.cpp
+++ b/llvm/unittests/Support/RegexTest.cpp
@@ -127,6 +127,9 @@
 
   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) {