On Sunday, 12 November 2017 at 11:01:39 UTC, Dibyendu Majumdar
wrote:
Hi,
I have recently started work on building a VM for Lua (actually
a derivative of Lua) in X86-64 assembly. I am using the dynasm
tool that is part of LuaJIT. I was wondering whether I could
also write this in D's inline assembly perhaps, but there is
one aspect that I am not sure how to do.
The assembly code uses static allocation of registers, but
because of the differences in how registers are used in Win64
versus Unix X64 - different registers are assigned depending on
the architecture. dynasm makes this easy to do using macros;
e.g. below.
|.if X64WIN
|.define CARG1, rcx // x64/WIN64 C call arguments.
|.define CARG2, rdx
|.define CARG3, r8
|.define CARG4, r9
|.else
|.define CARG1, rdi // x64/POSIX C call arguments.
|.define CARG2, rsi
|.define CARG3, rdx
|.define CARG4, rcx
|.endif
With above in place, the code can use the mnemonics to refer to
the registers rather than the registers themselves. This allows
the assembly code to be coded once for both architectures.
How would one do this in D inline assembly?
Thanks and Regards
Dibyendu
TBH I wonder if this is not worth a enhancement (or even a DIP)
to have in asm blocks a special alias syntax...
{
asm
{
version(...)
{
alias First = RDI;
alias Second = RSI;
// ...
}
else
{
alias First = RCX;
alias Second = RDX;
}
mov First, Second;
call aFunctionWithOneParam; // called with 2nd parent
param as 1st param
}
}
since the whole mixin solution make the custom asm unreadable
just because of this problem.
And Even maybe some special identifiers since extern(...) may
lead to problems...
