Index: llvm/trunk/lib/Support/APFloat.cpp
===================================================================
--- llvm/trunk/lib/Support/APFloat.cpp
+++ llvm/trunk/lib/Support/APFloat.cpp
@@ -2543,12 +2543,12 @@
 }
 
 bool IEEEFloat::convertFromStringSpecials(StringRef str) {
-  if (str.equals("inf") || str.equals("INFINITY")) {
+  if (str.equals("inf") || str.equals("INFINITY") || str.equals("+Inf")) {
     makeInf(false);
     return true;
   }
 
-  if (str.equals("-inf") || str.equals("-INFINITY")) {
+  if (str.equals("-inf") || str.equals("-INFINITY") || str.equals("-Inf")) {
     makeInf(true);
     return true;
   }
Index: llvm/trunk/unittests/ADT/APFloatTest.cpp
===================================================================
--- llvm/trunk/unittests/ADT/APFloatTest.cpp
+++ llvm/trunk/unittests/ADT/APFloatTest.cpp
@@ -849,6 +849,22 @@
   EXPECT_EQ(2.71828, convertToDoubleFromString("2.71828"));
 }
 
+TEST(APFloatTest, fromToStringSpecials) {
+  auto roundTrip = [] (const char* str) {
+    return convertToString(convertToDoubleFromString(str), 0, 3).c_str();
+  };
+  EXPECT_STREQ("+Inf", roundTrip("+Inf"));
+  EXPECT_STREQ("+Inf", roundTrip("INFINITY"));
+  EXPECT_STREQ("+Inf", roundTrip("inf"));
+  EXPECT_STREQ("-Inf", roundTrip("-Inf"));
+  EXPECT_STREQ("-Inf", roundTrip("-INFINITY"));
+  EXPECT_STREQ("-Inf", roundTrip("-inf"));
+  EXPECT_STREQ("NaN", roundTrip("NaN"));
+  EXPECT_STREQ("NaN", roundTrip("nan"));
+  EXPECT_STREQ("NaN", roundTrip("-NaN"));
+  EXPECT_STREQ("NaN", roundTrip("-nan"));
+}
+
 TEST(APFloatTest, fromHexadecimalString) {
   EXPECT_EQ( 1.0, APFloat(APFloat::IEEEdouble(),  "0x1p0").convertToDouble());
   EXPECT_EQ(+1.0, APFloat(APFloat::IEEEdouble(), "+0x1p0").convertToDouble());