diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9609,6 +9609,24 @@
     return Success(N == Val.getBitWidth() ? 0 : N + 1, E);
   }
 
+  case Builtin::BI__builtin_lround:
+  case Builtin::BI__builtin_lroundf:
+  case Builtin::BI__builtin_lroundl:
+  case Builtin::BI__builtin_llround:
+  case Builtin::BI__builtin_llroundf:
+  case Builtin::BI__builtin_llroundl: {
+    APFloat FPVal(0.0);
+    APSInt IVal(Info.Ctx.getIntWidth(E->getType()), 0);
+    bool IsExact = true;
+
+    if (!EvaluateFloat(E->getArg(0), FPVal, Info)) return false;
+    APFloat::opStatus RoundStatus =
+        FPVal.convertToInteger(IVal, APFloat::rmNearestTiesToAway, &IsExact);
+    if (RoundStatus != APFloat::opInexact && RoundStatus != APFloat::opOK) return false;
+
+    return Success(IVal, E);
+  }
+
   case Builtin::BI__builtin_fpclassify: {
     APFloat Val(0.0);
     if (!EvaluateFloat(E->getArg(5), Val, Info))
diff --git a/clang/test/SemaCXX/math-builtins.cpp b/clang/test/SemaCXX/math-builtins.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/math-builtins.cpp
@@ -0,0 +1,58 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+
+int main()
+{
+  constexpr float f1 = 12345.6789;
+  constexpr float f2 = 12345.4321;
+  constexpr float f3 = 0.5;
+  constexpr float f4 = -0.5;
+
+  static_assert(__builtin_llround(f1) == 12346, "");
+  static_assert(__builtin_llroundf(f1) == 12346, "");
+  static_assert(__builtin_llroundl(f1) == 12346, "");
+
+  static_assert(__builtin_lround(f1) == 12346, "");
+  static_assert(__builtin_lroundf(f1) == 12346, "");
+  static_assert(__builtin_lroundl(f1) == 12346, "");
+
+  static_assert(__builtin_llround(f2) == 12345, "");
+  static_assert(__builtin_llroundf(f2) == 12345, "");
+  static_assert(__builtin_llroundl(f2) == 12345, "");
+
+  static_assert(__builtin_lround(f2) == 12345, "");
+  static_assert(__builtin_lroundf(f2) == 12345, "");
+  static_assert(__builtin_lroundl(f2) == 12345, "");
+
+  static_assert(__builtin_llround(f3) == 1, "");
+  static_assert(__builtin_llroundf(f3) == 1, "");
+  static_assert(__builtin_llroundl(f3) == 1, "");
+
+  static_assert(__builtin_lround(f3) == 1, "");
+  static_assert(__builtin_lroundf(f3) == 1, "");
+  static_assert(__builtin_lroundl(f3) == 1, "");
+
+  static_assert(__builtin_llround(f4) == -1, "");
+  static_assert(__builtin_llroundf(f4) == -1, "");
+  static_assert(__builtin_llroundl(f4) == -1, "");
+
+  static_assert(__builtin_lround(f4) == -1, "");
+  static_assert(__builtin_lroundf(f4) == -1, "");
+  static_assert(__builtin_lroundl(f4) == -1, "");
+
+  static_assert(__builtin_llround(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundf(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundl(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  static_assert(__builtin_lround(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundf(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundl(__builtin_nanf("")) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  static_assert(__builtin_llround(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundf(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_llroundl(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+  static_assert(__builtin_lround(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundf(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+  static_assert(__builtin_lroundl(__FLT_MAX__) == 0, ""); // expected-error {{static_assert expression is not an integral constant expression}}
+
+}
\ No newline at end of file