[Mesa-dev] [PATCH 15/21] nir: Add a function for comparing cursors

[Connor Abbott]

On Tue, Mar 8, 2016 at 1:34 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>
>
> On Wed, Feb 24, 2016 at 10:45 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>>
>> On Sat, Feb 13, 2016 at 9:14 PM, Jason Ekstrand <jason at jlekstrand.net>
>> wrote:
>> > ---
>> >  src/compiler/nir/nir.c | 63
>> > ++++++++++++++++++++++++++++++++++++++++++++++++++
>> >  src/compiler/nir/nir.h |  2 ++
>> >  2 files changed, 65 insertions(+)
>> >
>> > diff --git a/src/compiler/nir/nir.c b/src/compiler/nir/nir.c
>> > index cd78475..468065a 100644
>> > --- a/src/compiler/nir/nir.c
>> > +++ b/src/compiler/nir/nir.c
>> > @@ -716,6 +716,69 @@ nir_cf_node_get_function(nir_cf_node *node)
>> >     return nir_cf_node_as_function(node);
>> >  }
>> >
>> > +/* Reduces a cursor by trying to convert everything to after and trying
>> > to
>> > + * go up to block granularity when possible.
>> > + */
>> > +static nir_cursor
>> > +reduce_cursor(nir_cursor cursor)
>> > +{
>> > +   switch (cursor.option) {
>> > +   case nir_cursor_before_block:
>> > +      if (exec_list_is_empty(&cursor.block->instr_list)) {
>> > +         /* Empty block.  After is as good as before. */
>> > +         cursor.option = nir_cursor_after_block;
>> > +      } else {
>> > +         /* Try to switch to after the previous block if there is one.
>> > +          * (This isn't likely, but it can happen.)
>> > +          */
>> > +         nir_cf_node *prev_node =
>> > nir_cf_node_prev(&cursor.block->cf_node);
>> > +         if (prev_node && prev_node->type == nir_cf_node_block) {
>>
>> How can the current node and the previous node both be blocks? It's an
>> invariant of the control-flow modification code that no two blocks
>> ever wind up next to each other.
>
>
> I can replace it with an assert if you'd like.

Ok... I was mostly confused about the comment saying "This isn't
likely, but it can happen." We already check this in the validator,
but go ahead and add an assert if you want. With this removed, this
gets my r-b.

> --Jason
>
>>
>>
>> > +            cursor.block = nir_cf_node_as_block(prev_node);
>> > +            cursor.option = nir_cursor_after_block;
>> > +         }
>> > +      }
>> > +      return cursor;
>> > +
>> > +   case nir_cursor_after_block:
>> > +      return cursor;
>> > +
>> > +   case nir_cursor_before_instr: {
>> > +      nir_instr *prev_instr = nir_instr_prev(cursor.instr);
>> > +      if (prev_instr) {
>> > +         /* Before this instruction is after the previous */
>> > +         cursor.instr = prev_instr;
>> > +         cursor.option = nir_cursor_after_instr;
>> > +      } else {
>> > +         /* No previous instruction.  Switch to before block */
>> > +         cursor.block = cursor.instr->block;
>> > +         cursor.option = nir_cursor_before_block;
>> > +      }
>> > +      return reduce_cursor(cursor);
>> > +   }
>> > +
>> > +   case nir_cursor_after_instr:
>> > +      if (nir_instr_next(cursor.instr) == NULL) {
>> > +         /* This is the last instruction, switch to after block */
>> > +         cursor.option = nir_cursor_after_block;
>> > +         cursor.block = cursor.instr->block;
>> > +      }
>> > +      return cursor;
>> > +
>> > +   default:
>> > +      unreachable("Inavlid cursor option");
>> > +   }
>> > +}
>> > +
>> > +bool
>> > +nir_cursors_equal(nir_cursor a, nir_cursor b)
>> > +{
>> > +   /* Reduced cursors should be unique */
>> > +   a = reduce_cursor(a);
>> > +   b = reduce_cursor(b);
>> > +
>> > +   return a.block == b.block && a.option == b.option;
>> > +}
>> > +
>> >  static bool
>> >  add_use_cb(nir_src *src, void *state)
>> >  {
>> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
>> > index 4c6c22f..c856b83 100644
>> > --- a/src/compiler/nir/nir.h
>> > +++ b/src/compiler/nir/nir.h
>> > @@ -1803,6 +1803,8 @@ typedef struct {
>> >     };
>> >  } nir_cursor;
>> >
>> > +bool nir_cursors_equal(nir_cursor a, nir_cursor b);
>> > +
>> >  static inline nir_cursor
>> >  nir_before_block(nir_block *block)
>> >  {
>> > --
>> > 2.5.0.400.gff86faf
>> >
>> > _______________________________________________
>> > mesa-dev mailing list
>> > mesa-dev at lists.freedesktop.org
>> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
>