Exit early from start line search for FunctionNameKind::None

[bcain]

Summary

rL294231 introduced a regression -- memory consumption for llvm-objdump during disassembly of ~500MB hexagon elf file was ~1.5GiB higher after that commit.

This change restores the previous behavior -- exit the search early for FunctionNameKind::None, saving some memory allocation.

[dblaikie]

Doesn't seem clear from the API whether passing FunctionNameKind::None should also not retrieve the start line of the function. Perhaps some renaming is in order to make that explicit/clear?

lib/DebugInfo/DWARF/DWARFContext.cpp

DWARFCompileUnit *DWARFContext::getCompileUnitForAddress(uint64_t Address) {
   return getCompileUnitForOffset(CUOffset);
 }
 
 static bool getFunctionNameAndStartLineForAddress(DWARFCompileUnit *CU,
                                                   uint64_t Address,
                                                   FunctionNameKind Kind,
                                                   std::string &FunctionName,
                                                   uint32_t &StartLine) {
+  if (Kind == FunctionNameKind::None)
+    return false;
+
   // The address may correspond to instruction in some inlined function,
   // so we have to build the chain of inlined functions and take the
   // name of the topmost function in it.
   SmallVector<DWARFDie, 4> InlinedChain;
   CU->getInlinedChainForAddress(Address, InlinedChain);
   if (InlinedChain.empty())
     return false;
 
   const DWARFDie &DIE = InlinedChain[0];
   bool FoundResult = false;
   const char *Name = nullptr;
-  if (Kind != FunctionNameKind::None && (Name = DIE.getSubroutineName(Kind))) {
+  if ((Name = DIE.getSubroutineName(Kind))) {
     FunctionName = Name;
     FoundResult = true;
   }
   if (auto DeclLineResult = DIE.getDeclLine()) {
     StartLine = DeclLineResult;
     FoundResult = true;
   }