Fix APFloat from string conversion for Inf

The method IEEEFloat::convertFromStringSpecials() does not recognize
the "+Inf" and "-Inf" strings but these strings are printed for
the double Infinities by the IEEEFloat::toString().

This patch adds the "+Inf" and "-Inf" strings to the list of recognized
patterns in IEEEFloat::convertFromStringSpecials().

Re-landing after fix.

Reviewers: sberg, bogner, majnemer, timshen, rnk, skatkov, gottesmm, bkramer, scanon, anna
Reviewed By: anna
Subscribers: mkazantsev, FlameTop, llvm-commits, reames, apilipenko
Differential Revision: https://reviews.llvm.org/D38030

llvm-svn: 321054

llvm/lib/Support/APFloat.cpp

@@ -2546,12 +2546,12 @@ IEEEFloat::convertFromDecimalString(StringRef str, roundingMode rounding_mode) {
 }
 
 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;
   }

llvm/lib/Support/StringRef.cpp

@@ -586,7 +586,7 @@ bool StringRef::getAsDouble(double &Result, bool AllowInexact) const {
   APFloat::opStatus Status =
       F.convertFromString(*this, APFloat::rmNearestTiesToEven);
   if (Status != APFloat::opOK) {
-    if (!AllowInexact || Status != APFloat::opInexact)
+    if (!AllowInexact || !(Status & APFloat::opInexact))
       return true;
   }
 

llvm/unittests/ADT/APFloatTest.cpp

@@ -849,6 +849,23 @@ TEST(APFloatTest, fromDecimalString) {
   EXPECT_EQ(2.71828, convertToDoubleFromString("2.71828"));
 }
 
+TEST(APFloatTest, fromToStringSpecials) {
+  auto expects = [] (const char *first, const char *second) {
+    std::string roundtrip = convertToString(convertToDoubleFromString(second), 0, 3);
+    EXPECT_STREQ(first, roundtrip.c_str());
+  };
+  expects("+Inf", "+Inf");
+  expects("+Inf", "INFINITY");
+  expects("+Inf", "inf");
+  expects("-Inf", "-Inf");
+  expects("-Inf", "-INFINITY");
+  expects("-Inf", "-inf");
+  expects("NaN", "NaN");
+  expects("NaN", "nan");
+  expects("NaN", "-NaN");
+  expects("NaN", "-nan");
+}
+
 TEST(APFloatTest, fromHexadecimalString) {
   EXPECT_EQ( 1.0, APFloat(APFloat::IEEEdouble(),  "0x1p0").convertToDouble());
   EXPECT_EQ(+1.0, APFloat(APFloat::IEEEdouble(), "+0x1p0").convertToDouble());

llvm/unittests/ADT/StringRefTest.cpp

@@ -875,7 +875,12 @@ struct GetDoubleStrings {
                      {"0.0", false, false, 0.0},
                      {"-0.0", false, false, -0.0},
                      {"123.45", false, true, 123.45},
-                     {"123.45", true, false, 123.45}};
+                     {"123.45", true, false, 123.45},
+                     {"1.8e308", true, false, std::numeric_limits<double>::infinity()},
+                     {"1.8e308", false, true, std::numeric_limits<double>::infinity()},
+                     {"0x0.0000000000001P-1023", false, true, 0.0},
+                     {"0x0.0000000000001P-1023", true, false, 0.0},
+                    };
 
 TEST(StringRefTest, getAsDouble) {
   for (const auto &Entry : DoubleStrings) {