Re: [Qemu-devel] [PATCH] tcg: Fix complilation with TCG

From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Richard Henderson <richard.henderson@linaro.org>,
	Laurent Vivier <lvivier@redhat.com>, Peter Xu <peterx@redhat.com>,
	QEMU Developers <qemu-devel@nongnu.org>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	Juan Quintela <quintela@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] tcg: Fix complilation with TCG
Date: Fri, 24 Nov 2017 11:09:58 +0100	[thread overview]
Message-ID: <b4ce1a99-9be7-c7eb-1867-5c873623d2a7@redhat.com> (raw)
In-Reply-To: <CAFEAcA_H2pF6qsW_pC9u6nRS7xwU5SHN8L6Eo6e==3Y-tqRv4w@mail.gmail.com>

On 24/11/2017 11:07, Peter Maydell wrote:
> On 23 November 2017 at 22:08, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On 22/11/2017 13:14, Peter Maydell wrote:
>>>> We do this all of the time for more regular tests that are obviously
>>>> compile-time.  I am a really big fan of this, because it makes sure that the
>>>> (usually 32-bit) else branch continues to compile.
>>> I'm happy with code that is "we assume the compiler is going to
>>> be sensible here so we don't have to use #ifdefs in the name
>>> of performance". I just don't think we should write code that
>>> can't compile at all if the compiler happens to not identify
>>> the codepath as dead. There's no guarantee by the compiler
>>> that it's going to do that.
>> There's plenty of cases where "if (kvm_enabled())" code would fail to
>> link if the compiler didn't do that optimization.
>
> I think that's a step less weird than "assert(kvm_enabled())",
> but I tend to think of that kind of thing as "if the compiler
> ever did decide not to link it we'd add missing stub functions".

I'll take a look at moving all the notdirty_* stuff under #ifdef
CONFIG_TCG then, for now we can proceed with Juan's patch.

Thanks,

Paolo