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glsl: Pack flat "varyings" of mixed types together.

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This patch enhances the varying packing code so that flat varyings of
uint, int, and float types can be packed together.

We accomplish this in lower_packed_varyings.cpp by making the type of
all flat varyings ivec4, and then using information-preserving type
conversions (e.g. ir_unop_bitcast_f2i) to convert all other types to
ints.

The varying_matches::compute_packing_class() function is updated to
reflect the fact that varying packing no longer needs to segregate
varyings of different base types.

Fixes piglit test varying-packing-mixed-types.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

v2: Split lower_packed_varyings_visitor::bitwise_assign into
pack/unpack variants.
This commit is contained in:
Paul Berry
2012-12-18 16:37:52 -08:00
parent 18720555dd
commit c35abcd1b0
2 changed files with 101 additions and 14 deletions
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20
src/glsl/link_varyings.cpp
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@@ -777,17 +777,25 @@ varying_matches::store_locations(unsigned producer_base,
unsigned
varying_matches::compute_packing_class(ir_variable *var)
{
/* In this initial implementation we conservatively assume that variables
* can only be packed if their base type (float/int/uint/bool) matches and
* their interpolation and centroid qualifiers match.
/* Without help from the back-end, there is no way to pack together
* variables with different interpolation types, because
* lower_packed_varyings must choose exactly one interpolation type for
* each packed varying it creates.
*
* TODO: relax these restrictions when the driver back-end permits.
* However, we can safely pack together floats, ints, and uints, because:
*
* - varyings of base type "int" and "uint" must use the "flat"
* interpolation type, which can only occur in GLSL 1.30 and above.
*
* - On platforms that support GLSL 1.30 and above, lower_packed_varyings
* can store flat floats as ints without losing any information (using
* the ir_unop_bitcast_* opcodes).
*
* Therefore, the packing class depends only on the interpolation type.
*/
unsigned packing_class = var->centroid ? 1 : 0;
packing_class *= 4;
packing_class += var->interpolation;
packing_class *= GLSL_TYPE_ERROR;
packing_class += var->type->get_scalar_type()->base_type;
return packing_class;
}