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/MipsTargetMachine.cpp

@@ -140,10 +140,9 @@ MipsTargetMachine::getSubtargetImpl(const Function &F) const {
   // FIXME: This is related to the code below to reset the target options,
   // we need to know whether or not the soft float flag is set on the
   // function, so we can enable it as a subtarget feature.
-  Attribute SFAttr = F.getFnAttribute("use-soft-float");
-  bool softFloat = !SFAttr.hasAttribute(Attribute::None)
-                       ? SFAttr.getValueAsString() == "true"
-                       : Options.UseSoftFloat;
+  bool softFloat =
+      F.hasFnAttribute("use-soft-float") &&
+      F.getFnAttribute("use-soft-float").getValueAsString() == "true";
 
   if (hasMips16Attr)
     FS += FS.empty() ? "+mips16" : ",+mips16";