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[oota-llvm.git] / lib / Support / APFloat.cpp

diff --git a/lib/Support/APFloat.cpp b/lib/Support/APFloat.cpp
index bc8e1d0c25e727f529fe4805199f92cbb21577c0..676e2d4ba007ef2b48e2d164ada12e6e228f69bb 100644 (file)
--- a/lib/Support/APFloat.cpp
+++ b/lib/Support/APFloat.cpp
@@ -1354,6 +1354,7 @@ APFloat::addOrSubtractSpecials(const APFloat &rhs, bool subtract)
   case PackCategoriesIntoKey(fcZero, fcNaN):
   case PackCategoriesIntoKey(fcNormal, fcNaN):
   case PackCategoriesIntoKey(fcInfinity, fcNaN):
+    sign = false;
     category = fcNaN;
     copySignificand(rhs);
     return opOK;
@@ -1472,11 +1473,13 @@ APFloat::multiplySpecials(const APFloat &rhs)
   case PackCategoriesIntoKey(fcNaN, fcNormal):
   case PackCategoriesIntoKey(fcNaN, fcInfinity):
   case PackCategoriesIntoKey(fcNaN, fcNaN):
+    sign = false;
     return opOK;
 
   case PackCategoriesIntoKey(fcZero, fcNaN):
   case PackCategoriesIntoKey(fcNormal, fcNaN):
   case PackCategoriesIntoKey(fcInfinity, fcNaN):
+    sign = false;
     category = fcNaN;
     copySignificand(rhs);
     return opOK;
@@ -1510,23 +1513,22 @@ APFloat::divideSpecials(const APFloat &rhs)
   default:
     llvm_unreachable(0);
 
+  case PackCategoriesIntoKey(fcZero, fcNaN):
+  case PackCategoriesIntoKey(fcNormal, fcNaN):
+  case PackCategoriesIntoKey(fcInfinity, fcNaN):
+    category = fcNaN;
+    copySignificand(rhs);
   case PackCategoriesIntoKey(fcNaN, fcZero):
   case PackCategoriesIntoKey(fcNaN, fcNormal):
   case PackCategoriesIntoKey(fcNaN, fcInfinity):
   case PackCategoriesIntoKey(fcNaN, fcNaN):
+    sign = false;
   case PackCategoriesIntoKey(fcInfinity, fcZero):
   case PackCategoriesIntoKey(fcInfinity, fcNormal):
   case PackCategoriesIntoKey(fcZero, fcInfinity):
   case PackCategoriesIntoKey(fcZero, fcNormal):
     return opOK;
 
-  case PackCategoriesIntoKey(fcZero, fcNaN):
-  case PackCategoriesIntoKey(fcNormal, fcNaN):
-  case PackCategoriesIntoKey(fcInfinity, fcNaN):
-    category = fcNaN;
-    copySignificand(rhs);
-    return opOK;
-
   case PackCategoriesIntoKey(fcNormal, fcInfinity):
     category = fcZero;
     return opOK;
@@ -1564,6 +1566,7 @@ APFloat::modSpecials(const APFloat &rhs)
   case PackCategoriesIntoKey(fcZero, fcNaN):
   case PackCategoriesIntoKey(fcNormal, fcNaN):
   case PackCategoriesIntoKey(fcInfinity, fcNaN):
+    sign = false;
     category = fcNaN;
     copySignificand(rhs);
     return opOK;
@@ -3543,11 +3546,14 @@ void APFloat::toString(SmallVectorImpl<char> &Str,
   // Set FormatPrecision if zero.  We want to do this before we
   // truncate trailing zeros, as those are part of the precision.
   if (!FormatPrecision) {
-    // It's an interesting question whether to use the nominal
-    // precision or the active precision here for denormals.
-
-    // FormatPrecision = ceil(significandBits / lg_2(10))
-    FormatPrecision = (semantics->precision * 59 + 195) / 196;
+    // We use enough digits so the number can be round-tripped back to an
+    // APFloat. The formula comes from "How to Print Floating-Point Numbers
+    // Accurately" by Steele and White.
+    // FIXME: Using a formula based purely on the precision is conservative;
+    // we can print fewer digits depending on the actual value being printed.
+
+    // FormatPrecision = 2 + floor(significandBits / lg_2(10))
+    FormatPrecision = 2 + semantics->precision * 59 / 196;
   }
 
   // Ignore trailing binary zeros.