Change how symbol sizes are handled in lib/Object.

COFF and MachO only define symbol sizes for common symbols. Reflect that
in the class hierarchy by having a method for common symbols only in the base
and a general one in ELF.

This avoids the need of using a magic value for the size, which had a few
problems
* Most callers didn't check for it.
* The ones that did could not tell the magic value from a file actually having
  that value.

llvm-svn: 240529
diff --git a/llvm/tools/llvm-symbolizer/LLVMSymbolize.cpp b/llvm/tools/llvm-symbolizer/LLVMSymbolize.cpp
index 448cfe9..b6af342 100644
--- a/llvm/tools/llvm-symbolizer/LLVMSymbolize.cpp
+++ b/llvm/tools/llvm-symbolizer/LLVMSymbolize.cpp
@@ -94,7 +94,7 @@
     return;
   uint64_t SymbolAddress;
   if (error(Symbol.getAddress(SymbolAddress)) ||
-      SymbolAddress == UnknownAddressOrSize)
+      SymbolAddress == UnknownAddress)
     return;
   if (OpdExtractor) {
     // For big-endian PowerPC64 ELF, symbols in the .opd section refer to
@@ -109,15 +109,12 @@
       SymbolAddress = OpdExtractor->getAddress(&OpdOffset32);
   }
   uint64_t SymbolSize;
-  // Getting symbol size is linear for Mach-O files, so assume that symbol
-  // occupies the memory range up to the following symbol.
-  if (isa<MachOObjectFile>(Module))
+  // Onyl ELF has a size for every symbol so assume that symbol occupies the
+  // memory range up to the following symbol.
+  if (auto *E = dyn_cast<ELFObjectFileBase>(Module))
+    SymbolSize = E->getSymbolSize(Symbol);
+  else
     SymbolSize = 0;
-  else {
-    SymbolSize = Symbol.getSize();
-    if (SymbolSize == UnknownAddressOrSize)
-      return;
-  }
   StringRef SymbolName;
   if (error(Symbol.getName(SymbolName)))
     return;