NVPTX: Cleanup function names for PTX syntax

[jascha]

Summary

Cleanup local function names as is already done for GVs.
Fixes Bug 24731.

[jascha]

Correction: this only fixes PR24731 for functions with local linkage.

[jlebar]

Dupe of D17738, I believe. Would love to get this fixed, but I don't think it's going to be accepted unless it's done "right".

lib/Target/NVPTX/NVPTXAssignValidGlobalNames.cpp

if (GV.hasLocalLinkage()) {
       // setName doesn't do extra work if the name does not change.
       // Note: this does not create collisions - if setName is asked to set the
       // name to something that already exists, it adds a proper postfix to
       // avoid collisions.
       GV.setName(cleanUpName(GV.getName()));
     }
   }
 
+  // Do the same for local function names.
+  for (Module::iterator F = M.begin(), Fend = M.end(); F != Fend; ++F) {
+    if (F->hasLocalLinkage()) {
+      F->setName(cleanUpName(F->getName()));
+    }
+  }
+
   return true;
 }
 
 std::string NVPTXAssignValidGlobalNames::cleanUpName(StringRef Name) {
   std::string ValidName;
   raw_string_ostream ValidNameStream(ValidName);
   for (unsigned I = 0, E = Name.size(); I != E; ++I) {
     char C = Name[I];