sample_d is slower than the lowered version on gen7. For gen7, this improves
Xonotic benchmark with Ultimate effects by as much as 25%:
before the change: 40.06 fps
after the change: 51.10 fps
after the change with INTEL_DEBUG=no16: 44.46 fps
As sample_d is not allowed in SIMD16 mode, I firstly thought the difference
was from SIMD8 versus SIMD16. If that was the case, we would want to apply
brw_lower_texture_gradients() only on fragment shaders in SIMD16 mode.
But, as the numbers show, there is still 10% improvement when SIMD16 is forced
off after the change. Thus textureGrad() is lowered unconditionally for now.
Due to this and that I haven't tried it on Haswell, this is still RFC.
No piglit regressions.
Signed-off-by: Chia-I Wu <olva...@gmail.com>
---
.../dri/i965/brw_lower_texture_gradients.cpp | 54 ++++++++++++++--------
1 file changed, 36 insertions(+), 18 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
b/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
index 1589a20..f3fcb56 100644
--- a/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
+++ b/src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp
@@ -34,8 +34,8 @@ using namespace ir_builder;
class lower_texture_grad_visitor : public ir_hierarchical_visitor {
public:
- lower_texture_grad_visitor(bool has_sample_d_c)
- : has_sample_d_c(has_sample_d_c)
+ lower_texture_grad_visitor(bool has_sample_d, bool has_sample_d_c)
+ : has_sample_d(has_sample_d), has_sample_d_c(has_sample_d_c)
{
progress = false;
}
@@ -44,6 +44,7 @@ public:
bool progress;
+ bool has_sample_d;
bool has_sample_d_c;
private:
@@ -90,22 +91,33 @@ txs_type(const glsl_type *type)
ir_visitor_status
lower_texture_grad_visitor::visit_leave(ir_texture *ir)
{
- /* Only lower textureGrad with shadow samplers */
- if (ir->op != ir_txd || !ir->shadow_comparitor)
+ if (ir->op != ir_txd)
return visit_continue;
- /* Lower textureGrad() with samplerCubeShadow even if we have the sample_d_c
- * message. GLSL provides gradients for the 'r' coordinate. Unfortunately:
- *
- * From the Ivybridge PRM, Volume 4, Part 1, sample_d message description:
- * "The r coordinate contains the faceid, and the r gradients are ignored
- * by hardware."
- *
- * We likely need to do a similar treatment for samplerCube and
- * samplerCubeArray, but we have insufficient testing for that at the
moment.
- */
- bool need_lowering = !has_sample_d_c ||
- ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE;
+ bool need_lowering = false;
+
+ if (ir->shadow_comparitor) {
+ /* Lower textureGrad() with samplerCubeShadow even if we have the
+ * sample_d_c message. GLSL provides gradients for the 'r' coordinate.
+ * Unfortunately:
+ *
+ * From the Ivybridge PRM, Volume 4, Part 1, sample_d message
+ * description: "The r coordinate contains the faceid, and the r
+ * gradients are ignored by hardware."
+ */
+ if (ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE)
+ need_lowering = true;
+ else if (!has_sample_d_c)
+ need_lowering = true;
+ }
+ else {
+ /* We likely need to do a similar treatment for samplerCube and
+ * samplerCubeArray, but we have insufficient testing for that at the
+ * moment.
+ */
+ if (!has_sample_d)
+ need_lowering = true;
+ }
if (!need_lowering)
return visit_continue;
@@ -154,7 +166,9 @@ lower_texture_grad_visitor::visit_leave(ir_texture *ir)
expr(ir_unop_sqrt, dot(dPdy, dPdy)));
}
- /* lambda_base = log2(rho). We're ignoring GL state biases for now. */
+ /* lambda_base = log2(rho). It will be biased and clamped by values
+ * defined in SAMPLER_STATE to get the final lambda.
+ */
ir->op = ir_txl;
ir->lod_info.lod = expr(ir_unop_log2, rho);
@@ -168,8 +182,12 @@ bool
brw_lower_texture_gradients(struct brw_context *brw,
struct exec_list *instructions)
{
+ /* sample_d is slower than the lowered version on gen7, and is not allowed
+ * in SIMD16 mode. Treating it as unsupported improves the performance.
+ */
+ bool has_sample_d = brw->gen != 7;
bool has_sample_d_c = brw->gen >= 8 || brw->is_haswell;
- lower_texture_grad_visitor v(has_sample_d_c);
+ lower_texture_grad_visitor v(has_sample_d, has_sample_d_c);
visit_list_elements(&v, instructions);
--
1.8.3.1
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
