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/X86/X86TargetMachine.cpp

@@ -131,13 +131,15 @@ X86TargetMachine::getSubtargetImpl(const Function &F) const {
   // function before we can generate a subtarget. We also need to use
   // it as a key for the subtarget since that can be the only difference
   // between two functions.
-  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 the soft float attribute is set on the function turn on the soft float
+  // subtarget feature.
+  if (SoftFloat)
+    FS += FS.empty() ? "+soft-float" : ",+soft-float";
 
-  auto &I = SubtargetMap[CPU + FS + (SoftFloat ? "use-soft-float=true"
-                                               : "use-soft-float=false")];
+  auto &I = SubtargetMap[CPU + FS];
   if (!I) {
     // This needs to be done before we create a new subtarget since any
     // creation will depend on the TM and the code generation flags on the