On Fri, Aug 28, 2015 at 10:49 AM, Connor Abbott <cwabbo...@gmail.com> wrote:
>
> On Aug 27, 2015 11:45 AM, "Jason Ekstrand" <ja...@jlekstrand.net> wrote:
>>
>> On Tue, Aug 25, 2015 at 1:24 PM, Kenneth Graunke <kenn...@whitecape.org>
>> wrote:
>> > This is a lot more reasonable than returning an offset from NULL.
>> >
>> > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
>> > ---
>> > src/glsl/nir/nir.h | 4 ++--
>> > 1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
>> > index 40871f7..12ddeb2 100644
>> > --- a/src/glsl/nir/nir.h
>> > +++ b/src/glsl/nir/nir.h
>> > @@ -1219,14 +1219,14 @@ static inline nir_instr *
>> > nir_block_first_instr(nir_block *block)
>> > {
>> > struct exec_node *head = exec_list_get_head(&block->instr_list);
>> > - return exec_node_data(nir_instr, head, node);
>> > + return head ? exec_node_data(nir_instr, head, node) : NULL;
>>
>> node is the first element of nir_instr so this is a no-op. Perhaps we
>> should instead just add a
>>
>> STATIC_ASSERT(offsetof(nir_instr, node) == 0)
>>
>> and a comment.
>
> I don't think that's really necessary, unless we want to really
> micro-optimize this function... I'd rather we have the obviously-correct
> thing that expresses what we actually want to do (get at the parent struct,
> or return NULL if it doesn't exist). We can do this if the compiler isn't
> smart enough and it actually does hurt, but given that we're probably
> cache-miss limited already, I would very much doubt that the extra few
> instructions are worth it.
Sure, I don't care that much about it.
--Jason
>>
>> > }
>> >
>> > static inline nir_instr *
>> > nir_block_last_instr(nir_block *block)
>> > {
>> > struct exec_node *tail = exec_list_get_tail(&block->instr_list);
>> > - return exec_node_data(nir_instr, tail, node);
>> > + return tail ? exec_node_data(nir_instr, tail, node) : NULL;
>> > }
>> >
>> > #define nir_foreach_instr(block, instr) \
>> > --
>> > 2.5.0
>> >
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