[PATCH] D75246: Fix reporting inexact status in IEEEFloat::roundToIntegral

[Serge Pavlov via Phabricator via llvm-commits]

sepavloff created this revision.
sepavloff added reviewers: timshen, scanon, skatkov, craig.topper, andrew.w.kaylor.
Herald added subscribers: dexonsmith, hiraditya.
Herald added a project: LLVM.

Rounding is made by adding a large integer number and then subtracting
it. Usually the first addition reports inexact result but only the
status of the subtraction were returned. Now inexact result is reported
if either of these operations returns inexact result.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75246

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


Index: llvm/unittests/ADT/APFloatTest.cpp
===================================================================
--- llvm/unittests/ADT/APFloatTest.cpp
+++ llvm/unittests/ADT/APFloatTest.cpp
@@ -1525,6 +1525,62 @@
   P = APFloat::getInf(APFloat::IEEEdouble(), true);
   P.roundToIntegral(APFloat::rmTowardZero);
   EXPECT_TRUE(std::isinf(P.convertToDouble()) && P.convertToDouble() < 0.0);
+
+  APFloat::opStatus St;
+
+  P = APFloat(10.0);
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_EQ(10.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opOK, St);
+
+  P = APFloat::getNaN(APFloat::IEEEdouble());
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_TRUE(P.isNaN());
+  EXPECT_FALSE(P.isNegative());
+  EXPECT_EQ(APFloat::opOK, St);
+
+  P = APFloat::getNaN(APFloat::IEEEdouble(), true);
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_TRUE(P.isNaN());
+  EXPECT_TRUE(P.isNegative());
+  EXPECT_EQ(APFloat::opOK, St);
+
+  P = APFloat::getInf(APFloat::IEEEdouble());
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_TRUE(P.isInfinity());
+  EXPECT_FALSE(P.isNegative());
+  EXPECT_EQ(APFloat::opOK, St);
+
+  P = APFloat::getInf(APFloat::IEEEdouble(), true);
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_TRUE(P.isInfinity());
+  EXPECT_TRUE(P.isNegative());
+  EXPECT_EQ(APFloat::opOK, St);
+
+  P = APFloat(10.5);
+  St = P.roundToIntegral(APFloat::rmTowardZero);
+  EXPECT_EQ(10.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opInexact, St);
+
+  P = APFloat(10.5);
+  St = P.roundToIntegral(APFloat::rmTowardPositive);
+  EXPECT_EQ(11.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opInexact, St);
+
+  P = APFloat(10.5);
+  St = P.roundToIntegral(APFloat::rmTowardNegative);
+  EXPECT_EQ(10.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opInexact, St);
+
+  P = APFloat(10.5);
+  St = P.roundToIntegral(APFloat::rmNearestTiesToAway);
+  EXPECT_EQ(11.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opInexact, St);
+
+  P = APFloat(10.5);
+  St = P.roundToIntegral(APFloat::rmNearestTiesToEven);
+  EXPECT_EQ(10.0, P.convertToDouble());
+  EXPECT_EQ(APFloat::opInexact, St);
 }
 
 TEST(APFloatTest, isInteger) {
Index: llvm/lib/Support/APFloat.cpp
===================================================================
--- llvm/lib/Support/APFloat.cpp
+++ llvm/lib/Support/APFloat.cpp
@@ -1977,7 +1977,7 @@
   return fs;
 }
 
-/* Rounding-mode corrrect round to integral value.  */
+/* Rounding-mode correct round to integral value.  */
 IEEEFloat::opStatus IEEEFloat::roundToIntegral(roundingMode rounding_mode) {
   opStatus fs;
 
@@ -2007,7 +2007,8 @@
   bool inputSign = isNegative();
 
   fs = add(MagicConstant, rounding_mode);
-  if (fs != opOK && fs != opInexact)
+  opStatus IsInexact = static_cast<opStatus>(fs & opInexact);
+  if (fs != opOK && !IsInexact)
     return fs;
 
   fs = subtract(MagicConstant, rounding_mode);
@@ -2016,7 +2017,7 @@
   if (inputSign != isNegative())
     changeSign();
 
-  return fs;
+  return fs == opOK ? IsInexact : fs;
 }
 
 


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