--- /dev/null
+/*
+ * Copyright © 2019 Collabora, Ltd.
+ *
+ * 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.
+ *
+ * Authors (Collabora):
+ * Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/*
+ * Lowers SSBOs to globals, for hardware that lack native SSBO support. When
+ * lowering, *_ssbo_* instructions will become *_global_* instructions,
+ * augmented with load_ssbo_address.
+ *
+ * DOES NOT PERFORM BOUNDS CHECKING. DO NOT USE IN PRODUCTION ON UNTRUSTED
+ * CONTEXTS INCLUDING WEBGL 2.
+ */
+
+static nir_intrinsic_op
+lower_ssbo_op(nir_intrinsic_op op)
+{
+ switch (op) {
+ case nir_intrinsic_load_ssbo:
+ return nir_intrinsic_load_global;
+
+ case nir_intrinsic_store_ssbo:
+ return nir_intrinsic_store_global;
+
+ default:
+ unreachable("Invalid SSBO op");
+ }
+}
+
+/* Like SSBO property sysvals, though SSBO index may be indirect. C.f.
+ * nir_load_system_value */
+
+static inline nir_ssa_def *
+nir_load_ssbo_prop(nir_builder *b, nir_intrinsic_op op,
+ nir_src *idx, unsigned bitsize)
+{
+ nir_intrinsic_instr *load = nir_intrinsic_instr_create(b->shader, op);
+ load->num_components = 1;
+ nir_src_copy(&load->src[0], idx, load);
+ nir_ssa_dest_init(&load->instr, &load->dest, 1, bitsize, NULL);
+ nir_builder_instr_insert(b, &load->instr);
+ return &load->dest.ssa;
+}
+
+#define nir_ssbo_prop(b, prop, index, bitsize) \
+ nir_load_ssbo_prop(b, nir_intrinsic_##prop, index, bitsize)
+
+static nir_ssa_def *
+lower_ssbo_instr(nir_builder *b, nir_intrinsic_instr *intr)
+{
+ nir_intrinsic_op op = lower_ssbo_op(intr->intrinsic);
+ bool is_store = op == nir_intrinsic_store_global;
+
+ /* We have to calculate the address:
+ *
+ * &(SSBO[offset]) = &SSBO + offset
+ */
+
+ nir_src index = intr->src[is_store ? 1 : 0];
+ nir_src *offset_src = nir_get_io_offset_src(intr);
+ nir_ssa_def *offset = nir_ssa_for_src(b, *offset_src, 1);
+
+ nir_ssa_def *address =
+ nir_iadd(b,
+ nir_ssbo_prop(b, load_ssbo_address, &index, 64),
+ nir_u2u64(b, offset));
+
+ /* Create the replacement intrinsic */
+
+ nir_intrinsic_instr *global =
+ nir_intrinsic_instr_create(b->shader, op);
+
+ global->num_components = intr->num_components;
+ global->src[is_store ? 1 : 0] = nir_src_for_ssa(address);
+
+ if (is_store) {
+ nir_src_copy(&global->src[0], &intr->src[0], global);
+ nir_intrinsic_set_write_mask(global, nir_intrinsic_write_mask(intr));
+ } else {
+ nir_ssa_dest_init(&global->instr, &global->dest,
+ intr->dest.ssa.num_components,
+ intr->dest.ssa.bit_size, NULL);
+ }
+
+ nir_builder_instr_insert(b, &global->instr);
+ return is_store ? NULL : &global->dest.ssa;
+}
+
+static bool
+should_lower_ssbo_instr(const nir_instr *instr)
+{
+ if (instr->type != nir_instr_type_intrinsic)
+ return false;
+
+ const nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+
+ switch (intr->intrinsic) {
+ case nir_intrinsic_load_ssbo:
+ case nir_intrinsic_store_ssbo:
+ return true;
+ default:
+ return false;
+ }
+
+ return false;
+}
+
+bool
+nir_lower_ssbo(nir_shader *shader)
+{
+ bool progress = false;
+
+ nir_foreach_function(function, shader) {
+ nir_function_impl *impl = function->impl;
+ nir_builder b;
+ nir_builder_init(&b, impl);
+
+ nir_foreach_block(block, impl) {
+ nir_foreach_instr_safe(instr, block) {
+ if (!should_lower_ssbo_instr(instr)) continue;
+ progress = true;
+ b.cursor = nir_before_instr(instr);
+
+ nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+ nir_ssa_def *replace = lower_ssbo_instr(&b, intr);
+
+ if (replace) {
+ nir_ssa_def_rewrite_uses(&intr->dest.ssa,
+ nir_src_for_ssa(replace));
+ }
+
+ nir_instr_remove(instr);
+ }
+ }
+ }
+
+ return progress;
+}
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