On 05/31/2018 10:34 AM, Ian Romanick wrote:
> There are GLSL IR lowering passes for a lot (all?) of this that I added
> when I did GL_MESA_shader_integer_functions. Is there a reason to not
> use those?
Which I now see that you mentioned in the commit messages. Still, just
curious...
> On 05/08/2018 01:13 PM, Eric Anholt wrote:
>> If you don't have HW to do bfi, then lowering bitfieldInsert to bfi makes
>> things harder than keeping the "bits" argument around.
>>
>> This still uses bfm, but I've added the obvious lowering of bfm if you
>> need it.
>> ---
>> src/compiler/nir/nir.h | 5 +++++
>> src/compiler/nir/nir_opt_algebraic.py | 14 ++++++++++++++
>> 2 files changed, 19 insertions(+)
>>
>> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
>> index a379928cdcd9..ed95dbf955d8 100644
>> --- a/src/compiler/nir/nir.h
>> +++ b/src/compiler/nir/nir.h
>> @@ -1880,7 +1880,12 @@ typedef struct nir_shader_compiler_options {
>> bool lower_fmod32;
>> bool lower_fmod64;
>> bool lower_bitfield_extract;
>> + /** Lowers bitfield_insert to bfi/bfm */
>> bool lower_bitfield_insert;
>> + /** Lowers bitfield_insert to bfm, compares, and shifts. */
>> + bool lower_bitfield_insert_to_shifts;
>> + /** Lowers bfm to shifts and subtracts. */
>> + bool lower_bfm;
>> bool lower_uadd_carry;
>> bool lower_usub_borrow;
>> /** lowers fneg and ineg to fsub and isub. */
>> diff --git a/src/compiler/nir/nir_opt_algebraic.py
>> b/src/compiler/nir/nir_opt_algebraic.py
>> index 96232f0e549c..2824dcebb81b 100644
>> --- a/src/compiler/nir/nir_opt_algebraic.py
>> +++ b/src/compiler/nir/nir_opt_algebraic.py
>> @@ -492,6 +492,20 @@ optimizations = [
>> ('bfi', ('bfm', 'bits', 'offset'), 'insert', 'base')),
>> 'options->lower_bitfield_insert'),
>>
>> + # Alternative lowering that doesn't rely on bfi.
>> + (('bitfield_insert', 'base', 'insert', 'offset', 'bits'),
>> + ('bcsel', ('ilt', 31, 'bits'),
>> + 'insert',
>> + ('ior',
>> + ('iand', 'base', ('inot', ('bfm', 'bits', 'offset'))),
>> + ('iand', ('ishl', 'insert', 'offset'), ('bfm', 'bits', 'offset')))),
>> + 'options->lower_bitfield_insert_to_shifts'),
>> +
>> + # bfm lowering -- note that the NIR opcode is undefined if either arg is
>> 32.
>> + (('bfm', 'bits', 'offset'),
>> + ('ishl', ('isub', ('ishl', 1, 'bits'), 1), 'offset'),
>> + 'options->lower_bfm'),
>> +
>> (('ibitfield_extract', 'value', 'offset', 'bits'),
>> ('bcsel', ('ilt', 31, 'bits'), 'value',
>> ('ibfe', 'value', 'offset', 'bits')),
>>
>
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