Enhance constant folding of bitcast operations on vectors of floats.

Add getAllOnesValue of FP numbers to Constants and APFloat.
Add more tests.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125776 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/APFloat.h

@@ -246,6 +246,13 @@ namespace llvm {
     static APFloat getSmallestNormalized(const fltSemantics &Sem,
                                          bool Negative = false);
 
+    /// getAllOnesValue - Returns a float which is bitcasted from
+    /// an all one value int.
+    ///
+    /// \param BitWidth - Select float type
+    /// \param isIEEE   - If 128 bit number, select between PPC and IEEE
+    static APFloat getAllOnesValue(unsigned BitWidth, bool isIEEE = false);
+
     /// Profile - Used to insert APFloat objects, or objects that contain
     ///  APFloat objects, into FoldingSets.
     void Profile(FoldingSetNodeID& NID) const;