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25 * \file brw_lower_texture_gradients.cpp
29 #include "glsl/ir_builder.h"
30 #include "program/prog_instruction.h"
31 #include "brw_context.h"
33 using namespace ir_builder
;
35 class lower_texture_grad_visitor
: public ir_hierarchical_visitor
{
37 lower_texture_grad_visitor(bool has_sample_d_c
)
38 : has_sample_d_c(has_sample_d_c
)
43 ir_visitor_status
visit_leave(ir_texture
*ir
);
50 void emit(ir_variable
*, ir_rvalue
*);
54 * Emit a variable declaration and an assignment to initialize it.
57 lower_texture_grad_visitor::emit(ir_variable
*var
, ir_rvalue
*value
)
59 base_ir
->insert_before(var
);
60 base_ir
->insert_before(assign(var
, value
));
63 static const glsl_type
*
64 txs_type(const glsl_type
*type
)
67 switch (type
->sampler_dimensionality
) {
68 case GLSL_SAMPLER_DIM_1D
:
71 case GLSL_SAMPLER_DIM_2D
:
72 case GLSL_SAMPLER_DIM_RECT
:
73 case GLSL_SAMPLER_DIM_CUBE
:
76 case GLSL_SAMPLER_DIM_3D
:
80 unreachable("Should not get here: invalid sampler dimensionality");
83 if (type
->sampler_array
)
86 return glsl_type::get_instance(GLSL_TYPE_INT
, dims
, 1);
90 lower_texture_grad_visitor::visit_leave(ir_texture
*ir
)
92 /* Only lower textureGrad with cube maps or shadow samplers */
93 if (ir
->op
!= ir_txd
||
94 (ir
->sampler
->type
->sampler_dimensionality
!= GLSL_SAMPLER_DIM_CUBE
&&
95 !ir
->shadow_comparitor
))
96 return visit_continue
;
98 /* Lower textureGrad() with samplerCube* even if we have the sample_d_c
99 * message. GLSL provides gradients for the 'r' coordinate. Unfortunately:
101 * From the Ivybridge PRM, Volume 4, Part 1, sample_d message description:
102 * "The r coordinate contains the faceid, and the r gradients are ignored
105 bool need_lowering
= !has_sample_d_c
||
106 ir
->sampler
->type
->sampler_dimensionality
== GLSL_SAMPLER_DIM_CUBE
;
109 return visit_continue
;
111 void *mem_ctx
= ralloc_parent(ir
);
113 const glsl_type
*grad_type
= ir
->lod_info
.grad
.dPdx
->type
;
115 /* Use textureSize() to get the width and height of LOD 0; swizzle away
116 * the depth/number of array slices.
118 ir_texture
*txs
= new(mem_ctx
) ir_texture(ir_txs
);
119 txs
->set_sampler(ir
->sampler
->clone(mem_ctx
, NULL
),
120 txs_type(ir
->sampler
->type
));
121 txs
->lod_info
.lod
= new(mem_ctx
) ir_constant(0);
123 new(mem_ctx
) ir_variable(grad_type
, "size", ir_var_temporary
);
124 if (ir
->sampler
->type
->sampler_dimensionality
== GLSL_SAMPLER_DIM_CUBE
) {
125 base_ir
->insert_before(size
);
126 base_ir
->insert_before(assign(size
,
127 swizzle_for_size(expr(ir_unop_i2f
, txs
), 2),
129 base_ir
->insert_before(assign(size
, new(mem_ctx
) ir_constant(1.0f
), WRITEMASK_Z
));
131 emit(size
, expr(ir_unop_i2f
,
132 swizzle_for_size(txs
, grad_type
->vector_elements
)));
135 /* Scale the gradients by width and height. Effectively, the incoming
136 * gradients are s'(x,y), t'(x,y), and r'(x,y) from equation 3.19 in the
137 * GL 3.0 spec; we want u'(x,y), which is w_t * s'(x,y).
140 new(mem_ctx
) ir_variable(grad_type
, "dPdx", ir_var_temporary
);
141 emit(dPdx
, mul(size
, ir
->lod_info
.grad
.dPdx
));
144 new(mem_ctx
) ir_variable(grad_type
, "dPdy", ir_var_temporary
);
145 emit(dPdy
, mul(size
, ir
->lod_info
.grad
.dPdy
));
147 /* Calculate rho from equation 3.20 of the GL 3.0 specification. */
149 if (dPdx
->type
->is_scalar()) {
150 rho
= expr(ir_binop_max
, expr(ir_unop_abs
, dPdx
),
151 expr(ir_unop_abs
, dPdy
));
153 rho
= expr(ir_binop_max
, expr(ir_unop_sqrt
, dot(dPdx
, dPdx
)),
154 expr(ir_unop_sqrt
, dot(dPdy
, dPdy
)));
157 /* lambda_base = log2(rho). We're ignoring GL state biases for now.
159 * For cube maps the result of these formulas is giving us a value of rho
160 * that is twice the value we should use, so divide it by 2 or,
161 * alternatively, remove one unit from the result of the log2 computation.
164 if (ir
->sampler
->type
->sampler_dimensionality
== GLSL_SAMPLER_DIM_CUBE
) {
165 ir
->lod_info
.lod
= expr(ir_binop_add
,
166 expr(ir_unop_log2
, rho
),
167 new(mem_ctx
) ir_constant(-1.0f
));
169 ir
->lod_info
.lod
= expr(ir_unop_log2
, rho
);
173 return visit_continue
;
179 brw_lower_texture_gradients(struct brw_context
*brw
,
180 struct exec_list
*instructions
)
182 bool has_sample_d_c
= brw
->gen
>= 8 || brw
->is_haswell
;
183 lower_texture_grad_visitor
v(has_sample_d_c
);
185 visit_list_elements(&v
, instructions
);