[Mesa-dev] [PATCH 1/3] nir/register: Add a parent_instr field

Eric Anholt eric at anholt.net
Tue Feb 17 15:44:21 PST 2015

Connor Abbott <cwabbott0 at gmail.com> writes:

> On Tue, Feb 17, 2015 at 3:52 PM, Eric Anholt <eric at anholt.net> wrote:
>> Matt Turner <mattst88 at gmail.com> writes:
>>> From: Jason Ekstrand <jason at jlekstrand.net>
>>> This adds a parent_instr field similar to the one for ssa_def.  The
>>> difference here is that the parent_instr field on a nir_register can be
>>> NULL if the register does not have a unique definition or if that
>>> definition does not dominate all its uses.  We set this field in the
>>> out-of-SSA pass so that backends can get SSA-like information even after
>>> they have gone out of SSA.
>> This will be useful for me, too, for similar multi-step multiply code.
> Wait, I thought you were translating SSA NIR to your IR, no? If so,
> this isn't too useful.

I'm calling out-of-ssa in NIR currently, not that it's really required,
since my IR is trivially SSA due to lack of control flow and there are
no phi nodes in the NIR.  My theory is that I'll be able to extend NIR
to lower to the control flow primitives present in my hardware and
adreno (which is to say, like brc/brd on ivb, but without the hardware
per-channel execution masking), in which case I'll definitely be out of
SSA in NIR before going into vc4.
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