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Date: Thu, 09 Apr 2015 11:21:26 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 01/14] memory: Define API for
 MemoryRegionOps to take attrs and return status
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To: Peter Maydell <peter.maydell@linaro.org>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>, Patch Tracking <patches@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Greg Bellows <greg.bellows@linaro.org>, =?UTF-8?B?QWxleCBCZW5u?= =?UTF-8?B?w6ll?= <alex.bennee@linaro.org>, Richard Henderson <rth@twiddle.net>



On 09/04/2015 11:04, Peter Maydell wrote:
> We discussed this last time round, I think. Whether structs get
> passed in registers depends on the host CPU ABI/calling convention.

Because of C++, structs up to pointer size are in practice always passed
in registers.  64-bit structs may or may not.

The main advantage of structs is that it's impossible to mismatch the
parameter order.  That even trumps readability in my opinion.

I'm ambivalent, but I wouldn't mind at all using structs.

Paolo

>> > I find it more readable, you ca go:
>> >
>> > attrs.secure =3D 1;
>> > attrs.master_id =3D 0x77;
>> > if (!attrs.secure)
>> >
>> > instead of:
>> >
>> > attrs |=3D MEMTXATTRS_SECURE
>> > if (!(attrs & MEMTXATTRS_SECURE))
>> >
>> > etc...
>> >
>> > Or do you see any disadvantages with this?
> I prefer the traditional integer-and-bitops approach, then you
> know what you're getting everywhere...