[llvm] b239165 - Patch IEEEFloat::isSignificandAllZeros and IEEEFloat::isSignificandAllOnes (bug 34579)

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2020-09-30T16:07:15-07:00
New Revision: b23916504a1a9f29c7519ed83813774eecce1789

URL: https://github.com/llvm/llvm-project/commit/b23916504a1a9f29c7519ed83813774eecce1789
DIFF: https://github.com/llvm/llvm-project/commit/b23916504a1a9f29c7519ed83813774eecce1789.diff

LOG: Patch IEEEFloat::isSignificandAllZeros and IEEEFloat::isSignificandAllOnes (bug 34579)

Patch IEEEFloat::isSignificandAllZeros and IEEEFloat::isSignificandAllOnes to behave correctly in the case that the size of the significand is a multiple of the width of the integerParts making up the significand.

The patch to IEEEFloat::isSignificandAllOnes fixes bug 34579, and the patch to IEEE:Float:isSignificandAllZeros fixes the unit test "APFloatTest.x87Next" I added here. I have included both in this diff since the changes are very similar.

Patch by Andrew Briand

Added: 
    

Modified: 
    llvm/lib/Support/APFloat.cpp
    llvm/unittests/ADT/APFloatTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index adc6299662b2..c5adbe9cf746 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -842,7 +842,7 @@ bool IEEEFloat::isSignificandAllOnes() const {
   // 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 @@ bool IEEEFloat::isSignificandAllZeros() const {
   // 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])

diff  --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 4cd027d24230..475ad83e2d9d 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -4696,4 +4696,15 @@ TEST(APFloatTest, PPCDoubleDoubleFrexp) {
   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);
+}
 }