On 08/11/18 23:14, Jason Ekstrand wrote:
On Thu, Nov 8, 2018 at 7:22 AM Alejandro Piñeiro <[email protected]> wrote:
On OpenGL, a array of a simple type adds just one varying. So
gl_transform_feedback_varying_info struct defined at mtypes.h includes
the parameters Type (base_type) and Size (number of elements).
This commit checks this when the recursive add_var_xfb_outputs call
handles arrays, to ensure that just one is addded.
RFC: Until this point, all changes were reasonable, but this change is
(imho) ugly. My idea was introducing as less as possible changes on
the code, specially on its logic/flow. But this commit is almost a
hack. The ideal solution would be to change the focus of the recursive
function, focusing on varyings, and at each varying, recursively add
outputs. But that seems like an overkill for a pass that was
originally intended for consumers only caring about the outputs. So
perhaps ARB_gl_spirv should keep their own gathering pass, with
vayings and outputs, and let this one untouched for those that only
care on outputs.
---
src/compiler/nir/nir_gather_xfb_info.c | 52 ++++++++++++++++++++++++++++------
1 file changed, 43 insertions(+), 9 deletions(-)
diff --git a/src/compiler/nir/nir_gather_xfb_info.c
b/src/compiler/nir/nir_gather_xfb_info.c
index 948b802a815..cb0e2724cab 100644
--- a/src/compiler/nir/nir_gather_xfb_info.c
+++ b/src/compiler/nir/nir_gather_xfb_info.c
@@ -36,23 +36,59 @@ nir_gather_xfb_info_create(void *mem_ctx, uint16_t
output_count, uint16_t varyin
return xfb;
}
+static bool
+glsl_type_is_leaf(const struct glsl_type *type)
+{
+ if (glsl_type_is_struct(type) ||
+ (glsl_type_is_array(type) &&
+ (glsl_type_is_array(glsl_get_array_element(type)) ||
+ glsl_type_is_struct(glsl_get_array_element(type))))) {
I'm trying to understand exactly what this means. From what you wrote here
it looks like the following are all one varying:
float var[3];
vec2 var[3];
mat4 var[3];
Yes, GLSL returns one varying per each one (Size 3).
but the following are not
struct S {
float f;
vec4 v;
};
S var[3];
float var[3][5];
I guess that you are asking for thos two cases because this code is not
handling it properly. You are right. For the array of structs, our code is
crashing. For the array of arrays, it is enumerating four varyings. One
with three GL_FLOAT components, and three with five GL_FLOAT components,
instead of just three varyings with five components. In my defense, I
already mentioned that it was wip code, but preferred to agree on the way
to go before keep working on it.
For the GLSL case, the array of struct returns 6 varyings. And funny thing,
for the array of arrays, GLSL is handling the situation even worse. It
returns the following link error: "Failed to link: error: Transform
feedback varying var[0] undeclared." Just a quick skim on the spec, I
didn't see anything preventing using aoa with transform feedback varyings,
so I guess that this is a bug due all the rules OpenGL has in relation with
variable names.
Is this correct?
Yes. FWIW, I will give you another two examples, from the tests Im using as
reference.
## example 1 ##
struct Array {
float x2_out;
};
struct AoA {
Array x2_Array[2];
};
struct S {
float x1_out;
AoA x2_AoA[2];
float x3_out;
};
layout(xfb_offset = 0) out S s1;
layout(xfb_offset = 0, xfb_buffer = 2) out struct S2 {
float y1_out;
vec4 y2_out;
} s2;
GLSL returns the following varyings (on ARB_gl_spirv we target to get the
same, although without the names)
NumVarying=8, (Offset, Type, BufferIndex, Size, Name)
0:( 0, GL_FLOAT, 0, 1, s1.x1_out)
1:( 4, GL_FLOAT, 0, 1, s1.x2_AoA[0].x2_Array[0].x2_out)
2:( 8, GL_FLOAT, 0, 1, s1.x2_AoA[0].x2_Array[1].x2_out)
3:(12, GL_FLOAT, 0, 1, s1.x2_AoA[1].x2_Array[0].x2_out)
4:(16, GL_FLOAT, 0, 1, s1.x2_AoA[1].x2_Array[1].x2_out)
5:(20, GL_FLOAT, 0, 1, s1.x3_out)
6:( 0, GL_FLOAT, 1, 1, s2.y1_out)
7:( 4, GL_FLOAT_VEC4, 1, 1, s2.y2_out)
## example 2 ##
layout(xfb_offset = 0) out float x1_out;
layout(xfb_offset = 4) out float x2_out[2];
layout(xfb_offset = 12) out vec3 x3_out;
layout(xfb_buffer = 2) out;
layout(xfb_offset = 0, xfb_buffer = 2) out float y1_out;
layout(xfb_offset = 4) out vec4 y2_out
GLSL returns the following varyings (on ARB_gl_spirv we target to get the
same, although without the names)
NumVarying=5, (Offset, Type, BufferIndex, Size, Name)
0:( 0, GL_FLOAT, 0, 1, x1_out)
1:( 4, GL_FLOAT, 0, 2, x2_out)
2:(12, GL_FLOAT_VEC3, 0, 1, x3_out)
3:( 0, GL_FLOAT, 1, 1, y1_out)
4:( 4, GL_FLOAT_VEC4, 1, 1, y2_out)
+ return false;
+ } else {
+ return true;
+ }
+}
+
+static void
+add_var_xfb_varying(nir_xfb_info *xfb,
+ nir_variable *var,
+ unsigned offset,
+ const struct glsl_type *type)
+{
+ nir_xfb_varying_info *varying = &xfb->varyings[xfb->varying_count++];
+
+ varying->type = type;
+ varying->buffer = var->data.xfb_buffer;
+ varying->offset = offset;
+ xfb->buffers[var->data.xfb_buffer].varying_count++;
+}
+
static void
add_var_xfb_outputs(nir_xfb_info *xfb,
nir_variable *var,
unsigned *location,
unsigned *offset,
- const struct glsl_type *type)
+ const struct glsl_type *type,
+ bool varying_added)
{
if (glsl_type_is_array(type) || glsl_type_is_matrix(type)) {
unsigned length = glsl_get_length(type);
+ bool local_varying_added = varying_added;
+
const struct glsl_type *child_type = glsl_get_array_element(type);
+ if (glsl_type_is_leaf(child_type)) {
+
+ add_var_xfb_varying(xfb, var, *offset, type);
+ local_varying_added = true;
+ }
+
for (unsigned i = 0; i < length; i++)
- add_var_xfb_outputs(xfb, var, location, offset, child_type);
+ add_var_xfb_outputs(xfb, var, location, offset, child_type,
local_varying_added);
} else if (glsl_type_is_struct(type)) {
unsigned length = glsl_get_length(type);
for (unsigned i = 0; i < length; i++) {
const struct glsl_type *child_type = glsl_get_struct_field(type, i);
- add_var_xfb_outputs(xfb, var, location, offset, child_type);
+ add_var_xfb_outputs(xfb, var, location, offset, child_type,
varying_added);
}
} else {
assert(var->data.xfb_buffer < NIR_MAX_XFB_BUFFERS);
@@ -83,11 +119,9 @@ add_var_xfb_outputs(nir_xfb_info *xfb,
uint8_t comp_mask = ((1 << comp_slots) - 1) << var->data.location_frac;
unsigned location_frac = var->data.location_frac;
- nir_xfb_varying_info *varying = &xfb->varyings[xfb->varying_count++];
- varying->type = type;
- varying->buffer = var->data.xfb_buffer;
- varying->offset = *offset;
- xfb->buffers[var->data.xfb_buffer].varying_count++;
+ if (!varying_added) {
+ add_var_xfb_varying(xfb, var, *offset, type);
+ }
assert(attrib_slots <= 2);
for (unsigned s = 0; s < attrib_slots; s++) {
@@ -171,7 +205,7 @@ nir_gather_xfb_info(const nir_shader *shader, void
*mem_ctx)
unsigned location = var->data.location;
unsigned offset = var->data.offset;
- add_var_xfb_outputs(xfb, var, &location, &offset, var->type);
+ add_var_xfb_outputs(xfb, var, &location, &offset, var->type, false);
}
}
assert(xfb->output_count == num_outputs);
--
2.14.1
