On 10/08/2016 09:33 AM, Eduardo Lima Mitev wrote:
> On 10/08/2016 02:12 AM, Ian Romanick wrote:
>> From: Ian Romanick <ian.d.roman...@intel.com>
>>
>> This was found partially by inspection and partially by hitting a
>> problem while working on nir_op_pack_int64_2x32_split. The code
>> previously would 'continue' if (instr->src[i].src.is_ssa), but the code
>> immediately following in the loop treats instr->src[i] as an SSA value.
>>
>> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
>> Cc: mesa-sta...@lists.freedesktop.org
>> Cc: Iago Toral Quiroga <ito...@igalia.com>
>> ---
>> src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> index 4e68ffb..2cbcab1 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> @@ -1208,7 +1208,7 @@ fs_visitor::nir_emit_alu(const fs_builder &bld,
>> nir_alu_instr *instr)
>> * the unpack operation.
>> */
>> for (int i = 0; i < 2; i++) {
>> - if (instr->src[i].src.is_ssa)
>> + if (!instr->src[i].src.is_ssa)
>> continue;
>>
>
> Good catch!
But maybe not. Re-running this through the CI shows about 1,000 test
regressions due to assertion failures. I looked at the rest of the
loop, and I'm really not sure how this works:
for (int i = 0; i < 2; i++) {
if (instr->src[i].src.is_ssa)
continue;
const nir_instr *parent_instr = instr->src[i].src.ssa->parent_instr;
We skip this if the source is SSA, but then we use it as SSA.
if (parent_instr->type == nir_instr_type_alu)
continue;
const nir_alu_instr *alu_parent = nir_instr_as_alu(parent_instr);
We skip this if the parent is ALU, but then we use it as ALU. The
assertion failure occurs inside nir_instr_as_alu.
if (alu_parent->op == nir_op_unpack_double_2x32_split_x ||
alu_parent->op == nir_op_unpack_double_2x32_split_y)
continue;
if (!alu_parent->src[0].src.is_ssa)
continue;
op[i] = get_nir_src(alu_parent->src[0].src);
op[i] = offset(retype(op[i], BRW_REGISTER_TYPE_DF), bld,
alu_parent->src[0].swizzle[channel]);
if (alu_parent->op == nir_op_unpack_double_2x32_split_y)
op[i] = subscript(op[i], BRW_REGISTER_TYPE_UD, 1);
else
op[i] = subscript(op[i], BRW_REGISTER_TYPE_UD, 0);
}
Were you guys ever able to make this optimization trigger? I suspect
that the very first continue always occurs, so none of this actually
happens. Either way, it seems like this optimization should happen in
nir_opt_algebraic instead.
This has come up because I need to do something similar for int64. All
of the lowering passes for int64 will generate a lot of
unpack(pack(...)) type sequences. I'm doing the lowering in GLSL IR,
so I've also done the algebraic optimization in GLSL IR.
> Both patches are:
>
> Reviewed-by: Eduardo Lima Mitev <el...@igalia.com>
>
>> const nir_instr *parent_instr =
>> instr->src[i].src.ssa->parent_instr;
>>
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