--- /dev/null
+/*
+ * Copyright (C) 2021 Alyssa Rosenzweig <alyssa@rosenzweig.io>
+ *
+ * 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 "agx_compiler.h"
+#include "agx_builder.h"
+
+/* Trivial register allocator that never frees anything.
+ *
+ * TODO: Write a real register allocator.
+ * TODO: Handle phi nodes.
+ */
+
+void
+agx_ra(agx_context *ctx)
+{
+ unsigned *alloc = calloc(ctx->alloc, sizeof(unsigned));
+ unsigned usage = 6*2;
+
+ agx_foreach_instr_global_safe(ctx, ins) {
+ /* Lower away RA pseudo-instructions */
+ if (ins->op == AGX_OPCODE_P_COMBINE) {
+ /* TODO: Optimize out the moves! */
+ unsigned components = 0;
+
+ for (unsigned i = 0; i < 4; ++i) {
+ if (!agx_is_null(ins->src[i]))
+ components = i + 1;
+ }
+
+ unsigned size = ins->dest[0].size == AGX_SIZE_32 ? 2 : 1;
+ if (size == 2 && usage & 1) usage++;
+ unsigned base = usage;
+ assert(ins->dest[0].type == AGX_INDEX_NORMAL);
+ alloc[ins->dest[0].value] = base;
+ usage += (components * size);
+
+ /* Move the sources */
+ agx_builder b = agx_init_builder(ctx, agx_after_instr(ins));
+
+ for (unsigned i = 0; i < 4; ++i) {
+ if (agx_is_null(ins->src[i])) continue;
+ assert(ins->src[0].type == AGX_INDEX_NORMAL);
+ agx_mov_to(&b, agx_register(base + (i * size), ins->dest[0].size),
+ agx_register(alloc[ins->src[i].value], ins->src[0].size));
+ }
+
+ /* We've lowered away, delete the old */
+ agx_remove_instruction(ins);
+ continue;
+ } else if (ins->op == AGX_OPCODE_P_EXTRACT) {
+ assert(ins->dest[0].type == AGX_INDEX_NORMAL);
+ assert(ins->src[0].type == AGX_INDEX_NORMAL);
+ assert(ins->dest[0].size == ins->src[0].size);
+
+ unsigned size = ins->dest[0].size == AGX_SIZE_32 ? 2 : 1;
+ alloc[ins->dest[0].value] = alloc[ins->src[0].value] + (size * ins->imm);
+ agx_remove_instruction(ins);
+ continue;
+ }
+
+ agx_foreach_src(ins, s) {
+ if (ins->src[s].type == AGX_INDEX_NORMAL) {
+ unsigned v = alloc[ins->src[s].value];
+ ins->src[s] = agx_replace_index(ins->src[s], agx_register(v, ins->src[s].size));
+ }
+ }
+
+ agx_foreach_dest(ins, d) {
+ if (ins->dest[d].type == AGX_INDEX_NORMAL) {
+ unsigned size = ins->dest[d].size == AGX_SIZE_32 ? 2 : 1;
+ if (size == 2 && usage & 1) usage++;
+ unsigned v = usage;
+ unsigned comps = (ins->op == AGX_OPCODE_LD_VARY || ins->op == AGX_OPCODE_DEVICE_LOAD || ins->op == AGX_OPCODE_TEXTURE_SAMPLE) ? 4 : 1; // todo systematic
+ usage += comps * size;
+ alloc[ins->dest[d].value] = v;
+ ins->dest[d] = agx_replace_index(ins->dest[d], agx_register(v, ins->dest[d].size));
+ }
+ }
+ }
+
+ assert(usage < 256 && "dummy RA");
+ free(alloc);
+}