large Windows mingw64 project in C99 --- need ABI compatible D compiler

[NonNull via Digitalmars-d-learn]

Hello,

I have a large project written in C99 handed to me that 32-bit 
builds in Windows with the mingw32 compiler that comes with 
msys2. I'm working on 64-bit Windows 10.

Need to solve some nasty problems and move the build to 64 bits 
using the mingw64 compiler that comes with msys2.

Want to use D to improve some parts of this monster. But am 
confused about ABI issues.

Which D compiler should be used to be ABI compatible with 
mingw32? And which to be ABI compatible with mingw64?

The most important is the D compiler that is ABI compatible with 
the 64-bit mingw compiler because that is where this project is 
going.

How can I use D in this situation, where I need it to work 
directly with C data? building DLLs is not going to work here for 
that reason.