Since libDemangling is included in the Swift standard library,
ODR violations can occur on platforms that allow statically
linking stdlib if Swift code is linked with other compiler
libraries that also transitively pull in libDemangling, and if
the stdlib version and compiler version do not match exactly
(even down to commit drift between releases). This lets the
runtime conditionally segregate its copies of the libDemangling
symbols from those in the compiler using an inline namespace
without affecting usage throughout source.
This adds a new copy of LLVMSupport into the runtime. This is the final
step before changing the inline namespace for the runtime support. This
will allow us to avoid the ODR violations from the header definitions of
LLVMSupport.
LLVMSupport forked at: 22492eead218ec91d349c8c50439880fbeacf2b7
Changes made to LLVMSupport from that revision:
process.inc forward declares `_beginthreadex` due to compilation issues due to custom flag handling
API changes required that we alter the `Deallocate` routine to account
for the alignment.
This is a temporary state, meant to simplify the process. We do not use
the entire LLVMSupport library and there is no value in keeping the
entire library. Subsequent commits will prune the library to the needs
for the runtime.
We'd like to be able to compare TypeRefs with pointer equality,
but we can't link LLVMSupport, so make a lightweight TypeRefID
like FoldingSetID, that only supports the input types necessary
to unique TypeRefs.
rdar://problem/25924875
