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panfrost: Avoid redundant shader executions with mask=0x0

Browse source 
Only works for a few Midgard GPUs, but hey.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5124>
This commit is contained in:
Alyssa Rosenzweig 2020-05-21 15:49:30 -04:00
parent 3e4e849e6a
commit 1085f74239
4 changed files with 54 additions and 1 deletions
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8
src/gallium/drivers/panfrost/pan_assemble.c
View file

@ -196,6 +196,14 @@ panfrost_shader_compile(struct panfrost_context *ctx,
state->writes_depth = true;
if (s->info.outputs_written & BITFIELD64_BIT(FRAG_RESULT_STENCIL))
state->writes_stencil = true;
/* List of reasons we need to execute frag shaders when things
* are masked off */
state->fs_sidefx =
s->info.writes_memory ||
s->info.fs.uses_discard ||
s->info.fs.uses_demote;
break;
case MESA_SHADER_COMPUTE:
/* TODO: images */

36
src/gallium/drivers/panfrost/pan_cmdstream.c
View file

@ -620,6 +620,27 @@ panfrost_frag_meta_zsa_update(struct panfrost_context *ctx,
fragmeta->unknown2_3 |= MALI_DEPTH_FUNC(panfrost_translate_compare_func(zfunc));
}
static bool
panfrost_fs_required(
struct panfrost_shader_state *fs,
struct panfrost_blend_final *blend,
unsigned rt_count)
{
/* If we generally have side effects */
if (fs->fs_sidefx)
return true;
/* If colour is written we need to execute */
for (unsigned i = 0; i < rt_count; ++i) {
if (!blend[i].no_colour)
return true;
}
/* If depth is written and not implied we need to execute.
* TODO: Predicate on Z/S writes being enabled */
return (fs->writes_depth || fs->writes_stencil);
}
static void
panfrost_frag_meta_blend_update(struct panfrost_context *ctx,
struct mali_shader_meta *fragmeta,
@ -642,6 +663,21 @@ panfrost_frag_meta_blend_update(struct panfrost_context *ctx,
blend[c] = panfrost_get_blend_for_context(ctx, c, &shader_bo,
&shader_offset);
/* Disable shader execution if we can */
if (dev->quirks & MIDGARD_SHADERLESS
&& !panfrost_fs_required(fs, blend, rt_count)) {
fragmeta->shader = 0;
fragmeta->attribute_count = 0;
fragmeta->varying_count = 0;
fragmeta->texture_count = 0;
fragmeta->sampler_count = 0;
/* This feature is not known to work on Bifrost */
fragmeta->midgard1.work_count = 1;
fragmeta->midgard1.uniform_count = 0;
fragmeta->midgard1.uniform_buffer_count = 0;
}
/* If there is a blend shader, work registers are shared. We impose 8
* work registers as a limit for blend shaders. Should be lower XXX */

4
src/gallium/drivers/panfrost/pan_context.h
View file

@ -195,6 +195,10 @@ struct panfrost_shader_state {
unsigned stack_size;
unsigned shared_size;
/* Does the fragment shader have side effects? In particular, if output
* is masked out, is it legal to skip shader execution? */
bool fs_sidefx;
/* For Bifrost - output type for each RT */
enum bifrost_shader_type blend_types[BIFROST_MAX_RENDER_TARGET_COUNT];

7
src/panfrost/include/panfrost-quirks.h
View file

@ -50,6 +50,11 @@
/* What it says on the tin */
#define HAS_SWIZZLES (1 << 4)
/* Support for setting shader to NULL for masking out colour (while allowing
* Z/S updates to proceed) */
#define MIDGARD_SHADERLESS (1 << 5)
/* Quirk collections common to particular uarchs */
#define MIDGARD_QUIRKS (MIDGARD_BROKEN_FP16 | HAS_SWIZZLES)
@ -74,7 +79,7 @@ panfrost_get_quirks(unsigned gpu_id)
case 0x750:
case 0x860:
case 0x880:
return MIDGARD_QUIRKS;
return MIDGARD_QUIRKS | MIDGARD_SHADERLESS;
case 0x6000: /* G71 */
return BIFROST_QUIRKS | HAS_SWIZZLES;