Mesa (main): nir: add a pass to optimize "gl_FragDepth = gl_FragCoord.z" away
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gitlab-mirror at kemper.freedesktop.org
Wed Aug 11 09:23:19 UTC 2021
Module: Mesa
Branch: main
Commit: 7684d57a051fdeb7f4ecfc970fd51f0c3bb9dfad
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7684d57a051fdeb7f4ecfc970fd51f0c3bb9dfad
Author: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Date: Fri May 7 16:36:47 2021 +0200
nir: add a pass to optimize "gl_FragDepth = gl_FragCoord.z" away
gl_FragDepth default value is gl_FragCoord.z so if a shader does:
gl_FragDepth = gl_FragCoord.z
we can drop this assignment.
v2: use nir_ssa_scalar_resolved and don't do this is gl_FragDepth
is wrote multiple times (Jason)
v3: - move to its own pass (Jason)
- handle var = NULL (Rhys)
v4: refactoring (Jason)
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10697>
---
src/compiler/nir/meson.build | 1 +
src/compiler/nir/nir.h | 2 +
src/compiler/nir/nir_opt_fragdepth.c | 111 ++++++++++++++++++++++++++++++
src/mesa/state_tracker/st_glsl_to_nir.cpp | 1 +
4 files changed, 115 insertions(+)
diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
index cd588303672..339b37200e2 100644
--- a/src/compiler/nir/meson.build
+++ b/src/compiler/nir/meson.build
@@ -223,6 +223,7 @@ files_libnir = files(
'nir_opt_dead_cf.c',
'nir_opt_dead_write_vars.c',
'nir_opt_find_array_copies.c',
+ 'nir_opt_fragdepth.c',
'nir_opt_gcm.c',
'nir_opt_idiv_const.c',
'nir_opt_if.c',
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 006a25debc9..167806a32bb 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -5444,6 +5444,8 @@ bool nir_opt_deref(nir_shader *shader);
bool nir_opt_find_array_copies(nir_shader *shader);
+bool nir_opt_fragdepth(nir_shader *shader);
+
bool nir_opt_gcm(nir_shader *shader, bool value_number);
bool nir_opt_idiv_const(nir_shader *shader, unsigned min_bit_size);
diff --git a/src/compiler/nir/nir_opt_fragdepth.c b/src/compiler/nir/nir_opt_fragdepth.c
new file mode 100644
index 00000000000..96da27cf94e
--- /dev/null
+++ b/src/compiler/nir/nir_opt_fragdepth.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright © 2021 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/**
+ * This pass removes no-op assignment to gl_FragDepth.
+ *
+ * gl_FragDepth implicit value is gl_FragCoord.z, so if a shader only assign
+ * this value to gl_FragDepth, the store instruction is removed.
+ */
+
+static bool
+ssa_def_is_source_depth(nir_ssa_def *def)
+{
+ nir_ssa_scalar scalar = nir_ssa_scalar_resolved(def, 0);
+ nir_instr *instr = scalar.def->parent_instr;
+ if (instr->type != nir_instr_type_intrinsic)
+ return false;
+
+ nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+ if (intrin->intrinsic != nir_intrinsic_load_frag_coord)
+ return false;
+
+ /* Depth is gl_FragCoord.z */
+ return scalar.comp == 2;
+}
+
+bool
+nir_opt_fragdepth(nir_shader *shader)
+{
+ bool progress = false;
+ nir_intrinsic_instr *store_intrin = NULL;
+
+ if (shader->info.stage != MESA_SHADER_FRAGMENT)
+ goto end;
+
+ nir_function_impl *impl = nir_shader_get_entrypoint(shader);
+ nir_foreach_block(block, impl) {
+ nir_foreach_instr(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
+ continue;
+
+ nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+ if (intrin->intrinsic != nir_intrinsic_store_deref)
+ continue;
+
+ nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
+ if (!nir_deref_mode_is(deref, nir_var_shader_out))
+ continue;
+
+ nir_variable *var = nir_deref_instr_get_variable(deref);
+ if (var->data.location != FRAG_RESULT_DEPTH)
+ continue;
+
+ /* We found a write to gl_FragDepth */
+ if (store_intrin) {
+ /* This isn't the only write: give up on this optimization */
+ goto end;
+ } else {
+ if (ssa_def_is_source_depth(intrin->src[1].ssa)) {
+ /* We're writing gl_FragCoord.z in gl_FragDepth: remember
+ * intrin so we can try to remove it later. */
+ store_intrin = intrin;
+ } else {
+ /* We're writing something else: give up. */
+ goto end;
+ }
+ }
+ }
+ }
+
+ if (store_intrin) {
+ /* Found a single store to gl_FragDepth, and it writes gl_FragCoord.z to it.
+ * Remove it since that's the implicit value of gl_FragDepth.
+ */
+ nir_instr_remove(&store_intrin->instr);
+
+ nir_metadata_preserve(impl, nir_metadata_block_index |
+ nir_metadata_dominance |
+ nir_metadata_loop_analysis |
+ nir_metadata_instr_index);
+ progress = true;
+ }
+
+end:
+ if (!progress)
+ nir_shader_preserve_all_metadata(shader);
+ return progress;
+}
diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index caeb195518a..5f4419358aa 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -530,6 +530,7 @@ st_glsl_to_nir_post_opts(struct st_context *st, struct gl_program *prog,
NIR_PASS_V(nir, gl_nir_lower_atomics, shader_program, true);
NIR_PASS_V(nir, nir_opt_intrinsics);
+ NIR_PASS_V(nir, nir_opt_fragdepth);
/* Lower 64-bit ops. */
if (nir->options->lower_int64_options ||
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