Rework the routines that convert AP[S]Int into a string. Now, instead of

returning an std::string by value, it fills in a SmallString/SmallVector
passed in.  This significantly reduces string thrashing in some cases.

More specifically, this:
 - Adds an operator<< and a print method for APInt that allows you to 
   directly send them to an ostream.
 - Reimplements APInt::toString to be much simpler and more efficient
   algorithmically in addition to not thrashing strings quite as much.

This speeds up llvm-dis on kc++ by 7%, and may also slightly speed up the
asmprinter.  This also fixes a bug I introduced into the asmwriter in a
previous patch w.r.t. alias printing.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54873 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/ConstantRange.cpp

@@ -463,8 +463,7 @@ ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
 /// print - Print out the bounds to a stream...
 ///
 void ConstantRange::print(std::ostream &OS) const {
-  OS << "[" << Lower.toStringSigned(10) << "," 
-            << Upper.toStringSigned(10) << ")";
+  OS << "[" << Lower << "," << Upper << ")";
 }
 
 /// dump - Allow printing from a debugger easily...