Supports dynamic VC runtime. It implements atexits handling which is required to load msvcrt.lib successfully. (the object file containing atexit symbol somehow resolves to static vc runtim symbols) It also default to dynamic vc runtime which tends to be more robust.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D132525
Mingw headers are all lowercase, and can be used for cross compilation
from case sensitive file systems.
The official Windows SDK headers aren't self-consistent wrt upper/lower
case, so those headers can't be used on case sensitive systems without
a layer providing case insensitivity anyway.
This matches other includes of windows.h throughout the codebase.
Initial platform support for COFF/x86_64.
Completed features:
* Statically linked orc runtime.
* Full linking/initialization of static/dynamic vc runtimes and microsoft stl libraries.
* SEH exception handling.
* Full static initializers support
* dlfns
* JIT side symbol lookup/dispatch
Things to note:
* It uses vc runtime libraries found in vc toolchain installations.
* Bootstrapping state is separated because when statically linking orc runtime it needs microsoft stl functions to initialize the orc runtime, but static initializers need to be ran in order to fully initialize stl libraries.
* Process symbols can't be used blidnly on msvc platform; otherwise duplicate definition error gets generated. If process symbols are used, it's destined to get out-of-reach error at some point.
* Atexit currently not handled -- will be handled in the follow-up patches.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D130479
Lang Hames