Walter Bright wrote:
Frits van Bommel wrote:
His approach depends on DMD directly emitting x86 machine code, so it
can just emit 'RET' and be done with it.
LDC on the other hand needs to emit LLVM asm, which requires it to
specify an explicit return value. My approach is a way to extract that
return value from the inline asm, allowing it to emulate DMD behavior
within the LLVM IR.
Ok, so why not, for a function that returns an int, simply have the
compiler silently tack on the LLVM equivalent of "return EAX"?
Because LLVM doesn't allow specification of hardware registers in the
IR. Everything must be a virtual register. The way I proposed LDC
implement this is basically to tell the inline-asm IR "Put EAX in
%virtual-eax" and to then return that register.
It will in all likelyhood have the same effect though, assuming a tiny
bit of optimization and a minimally competent register allocator.
