pan/bi: Add register allocator

We model the machine as vector (with restrictions) to natively handle
mixed types and I/O and other goodies. We use LCRA for the heavylifting.
This commit adds only the modeling to feed into LCRA and spit LCRA
solutions back; next commit will integrate it with the IR.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4158>

src/panfrost/bifrost/bi_ra.c

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2020 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 "compiler.h"
+#include "panfrost/util/lcra.h"
+#include "util/u_memory.h"
+
+static void
+bi_compute_interference(bi_context *ctx, struct lcra_state *l)
+{
+        bi_compute_liveness(ctx);
+
+        bi_foreach_block(ctx, _blk) {
+                bi_block *blk = (bi_block *) _blk;
+                uint16_t *live = mem_dup(_blk->live_out, l->node_count * sizeof(uint16_t));
+
+                bi_foreach_instr_in_block_rev(blk, ins) {
+                        /* Mark all registers live after the instruction as
+                         * interfering with the destination */
+
+                        if (ins->dest && (ins->dest < l->node_count)) {
+                                for (unsigned i = 1; i < l->node_count; ++i) {
+                                        if (live[i])
+                                                lcra_add_node_interference(l, ins->dest, ins->writemask, i, live[i]);
+                                }
+                        }
+
+                        /* Update live_in */
+                        bi_liveness_ins_update(live, ins, l->node_count);
+                }
+
+                free(live);
+        }
+}
+
+enum {
+        BI_REG_CLASS_WORK = 0,
+} bi_reg_class;
+
+static struct lcra_state *
+bi_allocate_registers(bi_context *ctx, bool *success)
+{
+        unsigned node_count = bi_max_temp(ctx);
+
+        struct lcra_state *l =
+                lcra_alloc_equations(node_count, 1, 8, 16, 1);
+
+        l->class_start[BI_REG_CLASS_WORK] = 0;
+        l->class_size[BI_REG_CLASS_WORK] = 64 * 4; /* R0 - R63, all 32-bit */
+
+        bi_foreach_instr_global(ctx, ins) {
+                unsigned dest = ins->dest;
+
+                if (!dest || (dest >= node_count))
+                        continue;
+
+                l->class[dest] = BI_REG_CLASS_WORK;
+                lcra_set_alignment(l, dest, 2); /* 2^2 = 4 */
+                lcra_restrict_range(l, dest, 4);
+        }
+
+        bi_compute_interference(ctx, l);
+
+        *success = lcra_solve(l);
+
+        return l;
+}
+
+void
+bi_register_allocate(bi_context *ctx)
+{
+        struct lcra_state *l = NULL;
+        bool success = false;
+
+        do {
+                if (l) {
+                        lcra_free(l);
+                        l = NULL;
+                }
+
+                bi_invalidate_liveness(ctx);
+                l = bi_allocate_registers(ctx, &success);
+
+                /* TODO: Spilling */
+                assert(success);
+        } while(!success);
+
+        lcra_free(l);
+}

src/panfrost/bifrost/bifrost_compile.c

@@ -863,6 +863,7 @@ bifrost_compile_shader_nir(nir_shader *nir, panfrost_program *program, unsigned
 
         bi_print_shader(ctx, stdout);
         bi_schedule(ctx);
+        bi_register_allocate(ctx);
 
         ralloc_free(ctx);
 }

src/panfrost/bifrost/compiler.h

@@ -387,7 +387,7 @@ static inline unsigned
 bi_max_temp(bi_context *ctx)
 {
         unsigned alloc = MAX2(ctx->impl->reg_alloc, ctx->impl->ssa_alloc);
-        return ((alloc + 1 + ctx->temp_alloc) << 1) | BIR_IS_REG;
+        return ((alloc + 2 + ctx->temp_alloc) << 1);
 }
 
 static inline unsigned
@@ -508,6 +508,7 @@ uint16_t bi_bytemask_of_read_components(bi_instruction *ins, unsigned node);
 
 bool bi_opt_dead_code_eliminate(bi_context *ctx, bi_block *block);
 void bi_schedule(bi_context *ctx);
+void bi_register_allocate(bi_context *ctx);
 
 /* Liveness */
 

src/panfrost/bifrost/meson.build

@@ -24,6 +24,7 @@ libpanfrost_bifrost_files = files(
   'bi_liveness.c',
   'bi_print.c',
   'bi_opt_dce.c',
+  'bi_ra.c',
   'bi_schedule.c',
   'bi_tables.c',
   'bir.c',