Index: llvm/lib/Support/APFloat.cpp
===================================================================
--- llvm/lib/Support/APFloat.cpp
+++ llvm/lib/Support/APFloat.cpp
@@ -842,7 +842,7 @@
   // Test if the significand excluding the integral bit is all ones. This allows
   // us to test for binade boundaries.
   const integerPart *Parts = significandParts();
-  const unsigned PartCount = partCount();
+  const unsigned PartCount = partCountForBits(semantics->precision);
   for (unsigned i = 0; i < PartCount - 1; i++)
     if (~Parts[i])
       return false;
@@ -864,7 +864,7 @@
   // Test if the significand excluding the integral bit is all zeros. This
   // allows us to test for binade boundaries.
   const integerPart *Parts = significandParts();
-  const unsigned PartCount = partCount();
+  const unsigned PartCount = partCountForBits(semantics->precision);
 
   for (unsigned i = 0; i < PartCount - 1; i++)
     if (Parts[i])
Index: llvm/unittests/ADT/APFloatTest.cpp
===================================================================
--- llvm/unittests/ADT/APFloatTest.cpp
+++ llvm/unittests/ADT/APFloatTest.cpp
@@ -4696,4 +4696,15 @@
   EXPECT_EQ(0x3fe8000000000000ull, Result.bitcastToAPInt().getRawData()[0]);
   EXPECT_EQ(0x3c98000000000000ull, Result.bitcastToAPInt().getRawData()[1]);
 }
+
+TEST(APFloatTest, x87Largest) {
+  APFloat MaxX87Val = APFloat::getLargest(APFloat::x87DoubleExtended());
+  EXPECT_TRUE(MaxX87Val.isLargest());
+}
+
+TEST(APFloatTest, x87Next) {
+  APFloat F(APFloat::x87DoubleExtended(), "-1.0");
+  F.next(false);
+  EXPECT_TRUE(ilogb(F) == -1);
+}
 }