Teach DataLayout that zero-byte pointer sizes don't make sense.

Previously this would result in assertion failures or simply crashes
at various points in the optimizer when trying to create types of zero
bit width.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230936 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/DataLayout.cpp

@@ -259,6 +259,8 @@ void DataLayout::parseSpecifier(StringRef Desc) {
             "Missing size specification for pointer in datalayout string");
       Split = split(Rest, ':');
       unsigned PointerMemSize = inBytes(getInt(Tok));
+      if (!PointerMemSize)
+        report_fatal_error("Invalid pointer size of 0 bytes");
 
       // ABI alignment.
       if (Rest.empty())