Migrate existing backends that care about software floating point

to use the information in the module rather than TargetOptions.

We've had and clang has used the use-soft-float attribute for some
time now so have the backends set a subtarget feature based on
a particular function now that subtargets are created based on
functions and function attributes.

For the one middle end soft float check go ahead and create
an overloadable TargetLowering::useSoftFloat function that
just checks the TargetSubtargetInfo in all cases.

Also remove the command line option that hard codes whether or
not soft-float is set by using the attribute for all of the
target specific test cases - for the generic just go ahead and
add the attribute in the one case that showed up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237079 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsISelLowering.cpp

@@ -3598,6 +3598,10 @@ unsigned MipsTargetLowering::getJumpTableEncoding() const {
   return TargetLowering::getJumpTableEncoding();
 }
 
+bool MipsTargetLowering::useSoftFloat() const {
+  return Subtarget.useSoftFloat();
+}
+
 void MipsTargetLowering::copyByValRegs(
     SDValue Chain, SDLoc DL, std::vector<SDValue> &OutChains, SelectionDAG &DAG,
     const ISD::ArgFlagsTy &Flags, SmallVectorImpl<SDValue> &InVals,