The collection of library function names in TargetLibraryInfo faces
similar challenges as RuntimeLibCalls in the IR component. The number of
function names is large, there are numerous customizations based on the
triple (including alternate names), and there is a lot of replicated
data in the signature table.
The ultimate goal would be to capture all lbrary function related
information in a .td file. This PR brings the current .def file to
TableGen, almost as a 1:1 replacement. However, there are some
improvements which are not possible in the current implementation:
- the function names are now stored as a long string together with an
offset table.
- the table of signatures is now deduplicated, using an offset table for
access.
The size of the object file decreases about 34kB with these changes. The
hash table of all function names is still constructed dynamically. A
static table like for RuntimeLibCalls is the next logical step.
The main motivation for this change is that I have to add a large number
of custom names for z/OS (like in RuntimeLibCalls.td), and the current
infrastructur does not support this very well.
Make `AppendZero` a class member instead of an argument to
`GetOrAddStringOffset` to reflect the intended usage that for a given
`StringToOffsetTable`, all strings must use the same value of
`AppendZero`.
Modify `EmitStringTableDef` to drop the `Indent` argument as its always
set to `""`, and to fail if it's called for a table with
non-null-terminated strings.
This mainly transitions the LLVM intrinsic string table from character
emission to string literal emission, which I confirmed happens for me
locally.
I moved the guts of StringToOffsetTable to a cpp file so I could move
the `EmitLongStrLiterals` cl::opt global to a non-vague linkage home in
the `TableGen` library. I had to add missing FormatVariadic.h includes
to account for moving other includes to a cpp file.
