[Mesa-dev] [PATCH] nir/search: Save/restore the variables_seen bitmask when matching

Jason Ekstrand jason at jlekstrand.net
Fri May 8 15:25:41 PDT 2015


On Fri, May 8, 2015 at 3:20 PM, Ian Romanick <idr at freedesktop.org> wrote:
> On 05/08/2015 11:55 AM, Jason Ekstrand wrote:
>> On Fri, May 8, 2015 at 11:53 AM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>>> total instructions in shared programs: 7152330 -> 7137006 (-0.21%)
>>> instructions in affected programs:     1330548 -> 1315224 (-1.15%)
>>> helped:                                5797
>>> HURT:                                  76
>>
>> I'm doing some looking into the hurt programs.  It seems as if there
>> are some very strange interatctions between flrp and ffma.  I'm still
>> working out exactly how to fix it up.
>
> Yes, I noticed this too.  Did you see my reply to Ken earlier today?
> The problem I noticed /seems/ restricted to cases where the would-be
> interpolant is scalar but the other values are vector.

It would surprise me a lot of that mattered.  At the point where we do
opt_algebraic in NIR, we've already scalarized things.  That said,
there is a *lot* going on in an optimization loop so anything's
possible.
--Jason

>> --Jason
>>
>>> GAINED:                                0
>>> LOST:                                  8
>>> ---
>>>  src/glsl/nir/nir_search.c | 11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> diff --git a/src/glsl/nir/nir_search.c b/src/glsl/nir/nir_search.c
>>> index d86655b..4c83349 100644
>>> --- a/src/glsl/nir/nir_search.c
>>> +++ b/src/glsl/nir/nir_search.c
>>> @@ -199,6 +199,10 @@ match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
>>>        }
>>>     }
>>>
>>> +   /* Stash off the current variables_seen bitmask.  This way we can
>>> +    * restore it prior to matching in the commutative case below. */
>>> +   unsigned variables_seen_stash = state->variables_seen;
>>> +
>>>     bool matched = true;
>>>     for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
>>>        /* If the source is an explicitly sized source, then we need to reset
>>> @@ -221,6 +225,13 @@ match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
>>>
>>>     if (nir_op_infos[instr->op].algebraic_properties & NIR_OP_IS_COMMUTATIVE) {
>>>        assert(nir_op_infos[instr->op].num_inputs == 2);
>>> +
>>> +      /* Restore the variables_seen bitmask.  If we don't do this, then we
>>> +       * could end up with an erroneous failure due to variables found in the
>>> +       * first match attempt above not matching those in the second.
>>> +       */
>>> +      state->variables_seen = variables_seen_stash;
>>> +
>>>        if (!match_value(expr->srcs[0], instr, 1, num_components,
>>>                         swizzle, state))
>>>           return false;
>>> --
>>> 2.4.0
>>>
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>


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