When building a location list, the first debug value for a variable was
passed to DebugLocStream::ListBuilder. Later on, in ListBuilder()'s
destructor, initializeDbgValue() was called with the passed debug value,
setting the DbgVariable's MInsn pointer. A non-null MInsn says that the
variable is described by a single debug value through the variable's
scope, which is not the case when we have begun building a location
In DwarfCompileUnit::constructVariableDIEImpl(), the presence of a
location list index is checked before emitting a single location, so
setting MInsn for variables expressed by location lists did not have any
effect in practice. However, as it is unnecessary with the current code
base, remove that initialization.
I have verified that `llvm-dwarfdump -v' produces the same location
output with respectively without this patch when building a
RelWithDebInfo-profiled clang-tblgen binary.