Jonas Maebe escreveu:
On 16 Nov 2008, at 14:52, Florian Klaempfl wrote:
Luiz Americo Pereira Camara schrieb:
Maybe the documentation
(http://www.freepascal.org/docs-html/ref/refsu50.html#x126-13300011.4.4)
can be modified to clarify this since the statement:
"A constant argument is passed by reference if its size is larger
than a pointer."
leads to the conclusion that double types (8 bytes) would be passed
as reference in 32bit code.
Well, the bigger problem is that this is target dependent.
And calling convention dependent. In most cases, how exactly constant
and value parameters are handled by the compiler is a private
implementation detail. You cannot count on how it is exactly implemented.
Ok. I was not counting in implementation details.
My point was that this could be a missing optimization opportunity: pass
by reference a 8 bytes parameter when the pointer size is 4. I also
tested with TPoint (8 bytes) and it's passed by reference unlike double
(also 8 bytes) that is passed by value always.
Probably i'm missing some information why double is treated differently
of a record of same size. I don't have compiler knowledge. All my
conclusions came from the documentation.
Luiz
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