pan/mdg: Lower stores from helpers

Required for correct behaviour of SSBOs in fragment shaders on Midgard.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8774>

4 files changed, 96 insertions, 0 deletions

diff --git a/src/panfrost/midgard/meson.build b/src/panfrost/midgard/meson.build
index 49c3034c87f..446ad527b8e 100644
--- a/src/panfrost/midgard/meson.build
+++ b/src/panfrost/midgard/meson.build
@@ -35,6 +35,7 @@ libpanfrost_midgard_files = files(
   'mir_promote_uniforms.c',
   'mir_squeeze.c',
   'midgard_nir_lower_image_bitsize.c',
+  'midgard_nir_lower_helper_writes.c',
   'midgard_opt_copy_prop.c',
   'midgard_opt_dce.c',
   'midgard_opt_perspective.c',
diff --git a/src/panfrost/midgard/midgard_compile.c b/src/panfrost/midgard/midgard_compile.c
index d0d5ec74d6b..d706e9371d4 100644
--- a/src/panfrost/midgard/midgard_compile.c
+++ b/src/panfrost/midgard/midgard_compile.c
@@ -317,6 +317,7 @@ optimise_nir(nir_shader *nir, unsigned quirks, bool is_blend)
 
         /* Midgard image ops coordinates are 16-bit instead of 32-bit */
         NIR_PASS(progress, nir, midgard_nir_lower_image_bitsize);
+        NIR_PASS(progress, nir, midgard_nir_lower_helper_writes);
 
         NIR_PASS(progress, nir, midgard_nir_lower_algebraic_early);
 
diff --git a/src/panfrost/midgard/midgard_nir.h b/src/panfrost/midgard/midgard_nir.h
index e8f692b4504..25f3668969b 100644
--- a/src/panfrost/midgard/midgard_nir.h
+++ b/src/panfrost/midgard/midgard_nir.h
@@ -6,3 +6,4 @@ bool midgard_nir_lower_algebraic_late(nir_shader *shader);
 bool midgard_nir_scale_trig(nir_shader *shader);
 bool midgard_nir_cancel_inot(nir_shader *shader);
 bool midgard_nir_lower_image_bitsize(nir_shader *shader);
+bool midgard_nir_lower_helper_writes(nir_shader *shader);
diff --git a/src/panfrost/midgard/midgard_nir_lower_helper_writes.c b/src/panfrost/midgard/midgard_nir_lower_helper_writes.c
new file mode 100644
index 00000000000..51c4b7db5b6
--- /dev/null
+++ b/src/panfrost/midgard/midgard_nir_lower_helper_writes.c
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2020-2021 Collabora, Ltd.
+ * Copyright © 2020 Valve Corporation
+ *
+ * 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 "compiler/nir/nir.h"
+#include "compiler/nir/nir_builder.h"
+#include "midgard_nir.h"
+
+static bool
+nir_lower_helper_writes(nir_builder *b, nir_instr *instr, UNUSED void *data)
+{
+        if (instr->type != nir_instr_type_intrinsic)
+                return false;
+
+        nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+        switch (intr->intrinsic) {
+        case nir_intrinsic_global_atomic_add:
+        case nir_intrinsic_global_atomic_and:
+        case nir_intrinsic_global_atomic_comp_swap:
+        case nir_intrinsic_global_atomic_exchange:
+        case nir_intrinsic_global_atomic_fadd:
+        case nir_intrinsic_global_atomic_fcomp_swap:
+        case nir_intrinsic_global_atomic_fmax:
+        case nir_intrinsic_global_atomic_fmin:
+        case nir_intrinsic_global_atomic_imax:
+        case nir_intrinsic_global_atomic_imin:
+        case nir_intrinsic_global_atomic_or:
+        case nir_intrinsic_global_atomic_umax:
+        case nir_intrinsic_global_atomic_umin:
+        case nir_intrinsic_global_atomic_xor:
+        case nir_intrinsic_image_atomic_add:
+        case nir_intrinsic_image_atomic_and:
+        case nir_intrinsic_image_atomic_comp_swap:
+        case nir_intrinsic_image_atomic_dec_wrap:
+        case nir_intrinsic_image_atomic_exchange:
+        case nir_intrinsic_image_atomic_fadd:
+        case nir_intrinsic_image_atomic_imax:
+        case nir_intrinsic_image_atomic_imin:
+        case nir_intrinsic_image_atomic_inc_wrap:
+        case nir_intrinsic_image_atomic_or:
+        case nir_intrinsic_image_atomic_umax:
+        case nir_intrinsic_image_atomic_umin:
+        case nir_intrinsic_image_atomic_xor:
+        case nir_intrinsic_image_store:
+        case nir_intrinsic_store_global:
+                break;
+        default:
+                return false;
+        }
+
+        b->cursor = nir_before_instr(instr);
+
+        nir_ssa_def *helper = nir_load_helper_invocation(b, 1);
+        nir_push_if(b, nir_inot(b, helper));
+        nir_instr_remove(instr);
+        nir_builder_instr_insert(b, instr);
+        nir_pop_if(b, NULL);
+
+        return true;
+}
+
+bool
+midgard_nir_lower_helper_writes(nir_shader *shader)
+{
+        if (shader->info.stage != MESA_SHADER_FRAGMENT)
+                return false;
+
+        return nir_shader_instructions_pass(shader,
+                        nir_lower_helper_writes,
+                        nir_metadata_none,
+                        NULL);
+}