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Message
From: Scott Furman<sfurman@r...>
Date: Mon Dec 22 22:36:28 CET 2003
Subject: [openrisc] Re: OpenRisc Digest, Vol 1, Issue 12
Heiko Panther wrote:> d) No one seemed to have any substantial reasons why the ABI
> shouldn't be changed. There were some concerns from Pablo Huerta,
> saying the ABI change wouldn't be the best solution. Scott said the
> calling conventions he's using for 64 bit values are more efficient
> than in the classic ABI.
In the existing 3.2 compiler, 64-bit values are passed to functions by
reference. That is, the calling function must store the argument in two
32-bit words on the stack and pass that stack address to the callee. In
the patch I submitted, 64-bit values are passed to callees as a register
pair. This both saves execution time and stack space.
I'm not sure the by-reference ABI was used, since the additional code to
pass 64-bit values as register pairs is very tiny.
-Scott
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