LDC2 win64 calling convention

[kinke]

On Wednesday, 28 November 2018 at 18:56:14 UTC, realhet wrote:
> 1. Is there register parameters? (I think no)

Of course, e.g., POD structs of power-of-2 sizes <= 8 bytes and 
integral scalars as well as float/double/vectors. The stack isn't 
used at all, aggregates > 8 bytes are passed by ref (caller makes 
a copy on its stack and passes a pointer to it to the callee); 
that seems not to be mentioned at all in the Wiki article.

> 2. What are the volatile regs? RAX, RCX, RDX, XMM6..XMM15?

See Microsoft's docs.

> 3. Is the stack pointer aligned to 16?

It is IIRC.

> 4. Is there a 32 byte shadow area on the stack?

Yes, IIRC.

---

LDC conforms to the regular Win64 ABI (incl. __vectorcall 
extension for vectors). The biggest difference is that 
`extern(D)` (as opposed to `extern(C)` or `extern(C++)`) reverses 
the arguments - `foo(1, 2, 3, 4)` becomes `foo(4, 3, 2, 1)`, so 
not the first 4 args are passed in registers if possible, but the 
last ones (incl. special cases wrt. struct-return + `this` 
pointers). Other than that, there are just very few special cases 
for delegates and dynamic arrays, which only apply to `extern(D)`.