APFloat: Add frexp

llvm-svn: 263950

1 files changed, 25 insertions, 1 deletions

diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 814c72cc4d3..ada392c519b 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -3942,7 +3942,12 @@ APFloat::makeZero(bool Negative) {
   category = fcZero;
   sign = Negative;
   exponent = semantics->minExponent-1;
-  APInt::tcSet(significandParts(), 0, partCount());  
+  APInt::tcSet(significandParts(), 0, partCount());
+}
+
+void APFloat::makeQuiet() {
+  assert(isNaN());
+  APInt::tcSetBit(significandParts(), semantics->precision - 2);
 }
 
 int llvm::ilogb(const APFloat &Arg) {
@@ -3981,3 +3986,22 @@ APFloat llvm::scalbn(APFloat X, int Exp, APFloat::roundingMode RoundingMode) {
   X.normalize(RoundingMode, lfExactlyZero);
   return X;
 }
+
+APFloat llvm::frexp(const APFloat &Val, int &Exp, APFloat::roundingMode RM) {
+  Exp = ilogb(Val);
+
+  // Quiet signalling nans.
+  if (Exp == APFloat::IEK_NaN) {
+    APFloat Quiet(Val);
+    Quiet.makeQuiet();
+    return Quiet;
+  }
+
+  if (Exp == APFloat::IEK_Inf)
+    return Val;
+
+  // 1 is added because frexp is defined to return a normalized fraction in
+  // +/-[0.5, 1.0), rather than the usual +/-[1.0, 2.0).
+  Exp = Exp == APFloat::IEK_Zero ? 0 : Exp + 1;
+  return scalbn(Val, -Exp, RM);
+}