significantly speed up constant folding of calls (and thus all clients that use

significantly speed up constant folding of calls (and thus all clients that use
ConstantFoldInstruction on calls) by avoiding Value::getName().  getName() constructs
and returns an std::string, which does heap allocation stuff.  This slightly speeds up
instcombine.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40924 91177308-0d34-0410-b5e6-96231b3b80d8