Teach APFloat how to create both QNaNs and SNaNs and with arbitrary-width

payloads.  APFloat's internal folding routines always make QNaNs now,
instead of sometimes making QNaNs and sometimes SNaNs depending on the
type.

llvm-svn: 97364

2 files changed, 45 insertions, 12 deletions

diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index f90973feab8..4f1b85431cc 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -626,17 +626,37 @@ APFloat::copySignificand(const APFloat &rhs)
 /* Make this number a NaN, with an arbitrary but deterministic value
    for the significand.  If double or longer, this is a signalling NaN,
    which may not be ideal.  If float, this is QNaN(0).  */
-void
-APFloat::makeNaN(unsigned type)
+void APFloat::makeNaN(bool SNaN, bool Negative, const APInt *fill)
 {
   category = fcNaN;
-  // FIXME: Add double and long double support for QNaN(0).
-  if (semantics->precision == 24 && semantics->maxExponent == 127) {
-    type |=  0x7fc00000U;
-    type &= ~0x80000000U;
-  } else
-    type = ~0U;
-  APInt::tcSet(significandParts(), type, partCount());
+  sign = Negative;
+
+  // Set the significand bits to the fill.
+  if (!fill || fill->getNumWords() < partCount())
+    APInt::tcSet(significandParts(), 0, partCount());
+  if (fill)
+    APInt::tcAssign(significandParts(), fill->getRawData(), partCount());
+
+  if (SNaN) {
+    // We always have to clear the QNaN bit to make it an SNaN.
+    APInt::tcClearBit(significandParts(), semantics->precision - 2);
+
+    // If there are no bits set in the payload, we have to set
+    // *something* to make it a NaN instead of an infinity;
+    // conventionally, this is the next bit down from the QNaN bit.
+    if (APInt::tcIsZero(significandParts(), partCount()))
+      APInt::tcSetBit(significandParts(), semantics->precision - 3);
+  } else {
+    // We always have to set the QNaN bit to make it a QNaN.
+    APInt::tcSetBit(significandParts(), semantics->precision - 2);
+  }
+}
+
+APFloat APFloat::makeNaN(const fltSemantics &Sem, bool SNaN, bool Negative,
+                         const APInt *fill) {
+  APFloat value(Sem, uninitialized);
+  value.makeNaN(SNaN, Negative, fill);
+  return value;
 }
 
 APFloat &
@@ -701,9 +721,14 @@ APFloat::APFloat(const fltSemantics &ourSemantics) {
   sign = false;
 }
 
+APFloat::APFloat(const fltSemantics &ourSemantics, uninitializedTag tag) {
+  assertArithmeticOK(ourSemantics);
+  // Allocates storage if necessary but does not initialize it.
+  initialize(&ourSemantics);
+}
 
 APFloat::APFloat(const fltSemantics &ourSemantics,
-                 fltCategory ourCategory, bool negative, unsigned type)
+                 fltCategory ourCategory, bool negative)
 {
   assertArithmeticOK(ourSemantics);
   initialize(&ourSemantics);
@@ -712,7 +737,7 @@ APFloat::APFloat(const fltSemantics &ourSemantics,
   if (category == fcNormal)
     category = fcZero;
   else if (ourCategory == fcNaN)
-    makeNaN(type);
+    makeNaN();
 }
 
 APFloat::APFloat(const fltSemantics &ourSemantics, const StringRef& text)
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index 3bce3f3ed3f..6a6384aa3f4 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -2344,13 +2344,21 @@ APInt::tcExtractBit(const integerPart *parts, unsigned int bit)
          & ((integerPart) 1 << bit % integerPartWidth)) != 0;
 }
 
-/* Set the given bit of a bignum.  */
+/* Set the given bit of a bignum. */
 void
 APInt::tcSetBit(integerPart *parts, unsigned int bit)
 {
   parts[bit / integerPartWidth] |= (integerPart) 1 << (bit % integerPartWidth);
 }
 
+/* Clears the given bit of a bignum. */
+void
+APInt::tcClearBit(integerPart *parts, unsigned int bit)
+{
+  parts[bit / integerPartWidth] &=
+    ~((integerPart) 1 << (bit % integerPartWidth));
+}
+
 /* Returns the bit number of the least significant set bit of a
    number.  If the input number has no bits set -1U is returned.  */
 unsigned int