Add i686-unknown-uefi target

This adds a new rustc target-configuration called 'i686-unknown_uefi'.
This is similar to existing x86_64-unknown_uefi target.

The i686-unknown-uefi target can be used to build Intel Architecture
32bit UEFI application. The ABI defined in UEFI environment (aka IA32)
is similar to cdecl.

We choose i686-unknown-uefi-gnu instead of i686-unknown-uefi to avoid
the intrinsics generated by LLVM. The detail of root-cause and solution
analysis is added as comment in the code.
For x86_64-unknown-uefi, we cannot use -gnu, because the ABI between
MSVC and GNU is totally different, and UEFI chooses ABI similar to MSVC.
For i686-unknown-uefi, the UEFI chooses cdecl ABI, which is same as
MSVC and GNU. According to LLVM code, the only differences between MSVC
and GNU are fmodf(f32), longjmp() and TLS, which have no impact to UEFI.
As such, using i686-unknown-uefi-gnu is the simplest way to pass the build.

Adding the undefined symbols, such as _aulldiv() to rust compiler-builtins
is out of scope. But it may be considered later.

The scope of this patch is limited to support target-configuration.

No standard library support is added in this patch. Such work can be
done in future enhancement.

Cc: Josh Triplett <josh.triplett@intel.com>
Reviewed-by: Josh Triplett <josh.triplett@intel.com>

0 files changed, 0 insertions, 0 deletions