How should _Decimal64 and _Decimal128 be aligned on stack?

[H.J. Lu]

On Sun, Mar 23, 2008 at 11:41:00PM +1100, Ben Elliston wrote:
> > DFP is beyond i386 psABI. Gcc aligns _Decimal32 to 4 byte, _Decimal64 to 8 bytes
> > and _Decimal128 to 16bytes. The question is what is the best alignment for them
> > when passing to a functions.
> 
> The original work I did for the x86-64 backend placed them at that
> alignment because that is the required alignment for loading those
> values into SSE registers.  Right?

That is a good question. For x86, _Decimal128 is passed on stack
and aligned at 4 byte. For x86-64, _Decimal128 is passed in SSE
registers. An implementation of _Decimal128 in 32bit may want
to use SSE registers.


H.J.