diff --git a/include/llvm/Support/Regex.h b/include/llvm/Support/Regex.h
index ffe09b19b68..82df2c67bd0 100644
--- a/include/llvm/Support/Regex.h
+++ b/include/llvm/Support/Regex.h
@@ -7,7 +7,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements a POSIX regular expression matcher.
+// This file implements a POSIX regular expression matcher.  Both Basic and
+// Extended POSIX regular expressions (ERE) are supported.  EREs were extended
+// to support backreferences in matches.
+// This implementation also supports matching strings with embedded NUL chars.
 //
 //===----------------------------------------------------------------------===//
 
@@ -33,12 +36,14 @@ namespace llvm {
       /// null string after any newline in the string in addition to its normal
       /// function, and the $ anchor matches the null string before any
       /// newline in the string in addition to its normal function.
-      Newline=2
+      Newline=2,
+      /// By default, the POSIX extended regular expression (ERE) syntax is
+      /// assumed. Pass this flag to turn on basic regular expressions (BRE)
+      /// instead.
+      BasicRegex=4
     };
 
-    /// Compiles the given POSIX Extended Regular Expression \p Regex.
-    /// This implementation supports regexes and matching strings with embedded
-    /// NUL characters.
+    /// Compiles the given regular expression \p Regex.
     Regex(StringRef Regex, unsigned Flags = NoFlags);
     ~Regex();
 
diff --git a/lib/Support/Regex.cpp b/lib/Support/Regex.cpp
index d293da07d68..0a5479a548f 100644
--- a/lib/Support/Regex.cpp
+++ b/lib/Support/Regex.cpp
@@ -27,7 +27,9 @@ Regex::Regex(StringRef regex, unsigned Flags) {
     flags |= REG_ICASE;
   if (Flags & Newline)
     flags |= REG_NEWLINE;
-  error = llvm_regcomp(preg, regex.data(), flags|REG_EXTENDED|REG_PEND);
+  if (!(Flags & BasicRegex))
+    flags |= REG_EXTENDED;
+  error = llvm_regcomp(preg, regex.data(), flags|REG_PEND);
 }
 
 Regex::~Regex() {
diff --git a/lib/Support/regcomp.c b/lib/Support/regcomp.c
index 46c91a9c497..74d9186aaaa 100644
--- a/lib/Support/regcomp.c
+++ b/lib/Support/regcomp.c
@@ -303,6 +303,7 @@ p_ere_exp(struct parse *p)
 	sopno pos;
 	int count;
 	int count2;
+	int backrefnum;
 	sopno subno;
 	int wascaret = 0;
 
@@ -370,7 +371,34 @@ p_ere_exp(struct parse *p)
 	case '\\':
 		REQUIRE(MORE(), REG_EESCAPE);
 		c = GETNEXT();
-		ordinary(p, c);
+		if (c >= '1' && c <= '9') {
+			/* \[0-9] is taken to be a back-reference to a previously specified
+			 * matching group. backrefnum will hold the number. The matching
+			 * group must exist (i.e. if \4 is found there must have been at
+			 * least 4 matching groups specified in the pattern previously).
+			 */
+			backrefnum = c - '0';
+			if (p->pend[backrefnum] == 0) {
+				SETERROR(REG_ESUBREG);
+				break;
+			}
+
+			/* Make sure everything checks out and emit the sequence
+			 * that marks a back-reference to the parse structure.
+			 */
+			assert(backrefnum <= p->g->nsub);
+			EMIT(OBACK_, backrefnum);
+			assert(p->pbegin[backrefnum] != 0);
+			assert(OP(p->strip[p->pbegin[backrefnum]]) != OLPAREN);
+			assert(OP(p->strip[p->pend[backrefnum]]) != ORPAREN);
+			(void) dupl(p, p->pbegin[backrefnum]+1, p->pend[backrefnum]);
+			EMIT(O_BACK, backrefnum);
+			p->g->backrefs = 1;
+		} else {
+			/* Other chars are simply themselves when escaped with a backslash.
+			 */
+			ordinary(p, c);
+		}
 		break;
 	case '{':		/* okay as ordinary except if digit follows */
 		REQUIRE(!MORE() || !isdigit((uch)PEEK()), REG_BADRPT);
diff --git a/unittests/Support/RegexTest.cpp b/unittests/Support/RegexTest.cpp
index 65b66c3eee8..38d95955f89 100644
--- a/unittests/Support/RegexTest.cpp
+++ b/unittests/Support/RegexTest.cpp
@@ -51,7 +51,6 @@ TEST_F(RegexTest, Basics) {
   EXPECT_EQ(1u, Matches.size());
   EXPECT_EQ(String, Matches[0].str());
 
-
   std::string NulPattern="X[0-9]+X([a-f])?:([0-9]+)";
   String="YX99a:513b";
   NulPattern[7] = '\0';
@@ -62,6 +61,28 @@ TEST_F(RegexTest, Basics) {
   EXPECT_TRUE(r5.match(String));
 }
 
+TEST_F(RegexTest, Backreferences) {
+  Regex r1("([a-z]+)_\\1");
+  SmallVector<StringRef, 4> Matches;
+  EXPECT_TRUE(r1.match("abc_abc", &Matches));
+  EXPECT_EQ(2u, Matches.size());
+  EXPECT_FALSE(r1.match("abc_ab", &Matches));
+
+  Regex r2("a([0-9])b\\1c\\1");
+  EXPECT_TRUE(r2.match("a4b4c4", &Matches));
+  EXPECT_EQ(2u, Matches.size());
+  EXPECT_EQ("4", Matches[1].str());
+  EXPECT_FALSE(r2.match("a2b2c3"));
+
+  Regex r3("a([0-9])([a-z])b\\1\\2");
+  EXPECT_TRUE(r3.match("a6zb6z", &Matches));
+  EXPECT_EQ(3u, Matches.size());
+  EXPECT_EQ("6", Matches[1].str());
+  EXPECT_EQ("z", Matches[2].str());
+  EXPECT_FALSE(r3.match("a6zb6y"));
+  EXPECT_FALSE(r3.match("a6zb7z"));
+}
+
 TEST_F(RegexTest, Substitution) {
   std::string Error;