vc4: Enforce one-uniform-per-instruction after optimization.

This lets us more intelligently decide which uniform values should be put
into temporaries, by choosing the most reused values to push to temps
first.

total uniforms in shared programs: 13457 -> 13433 (-0.18%)
uniforms in affected programs:     1524 -> 1500 (-1.57%)
total instructions in shared programs: 40198 -> 40019 (-0.45%)
instructions in affected programs:     6027 -> 5848 (-2.97%)

I noticed this opportunity because with the NIR work, some programs were
happening to make different uniform copy propagation choices that
significantly increased instruction counts.

1 files changed, 176 insertions, 0 deletions

diff --git a/src/gallium/drivers/vc4/vc4_qir_lower_uniforms.c b/src/gallium/drivers/vc4/vc4_qir_lower_uniforms.c
new file mode 100644
index 00000000000..d527889e76f
--- /dev/null
+++ b/src/gallium/drivers/vc4/vc4_qir_lower_uniforms.c
@@ -0,0 +1,176 @@
+/*
+ * Copyright © 2014 Broadcom
+ *
+ * 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.
+ */
+
+/**
+ * @file vc4_opt_algebraic.c
+ *
+ * This is the optimization pass for miscellaneous changes to instructions
+ * where we can simplify the operation by some knowledge about the specific
+ * operations.
+ *
+ * Mostly this will be a matter of turning things into MOVs so that they can
+ * later be copy-propagated out.
+ */
+
+#include "vc4_qir.h"
+#include "util/hash_table.h"
+#include "util/u_math.h"
+
+static inline uint32_t
+index_hash(const void *key)
+{
+        return (uintptr_t)key;
+}
+
+static inline bool
+index_compare(const void *a, const void *b)
+{
+        return a == b;
+}
+
+static void
+add_uniform(struct hash_table *ht, struct qreg reg)
+{
+        struct hash_entry *entry;
+        void *key = (void *)(uintptr_t)reg.index;
+
+        entry = _mesa_hash_table_search(ht, key);
+        if (entry) {
+                entry->data++;
+        } else {
+                _mesa_hash_table_insert(ht, key, (void *)(uintptr_t)1);
+        }
+}
+
+static void
+remove_uniform(struct hash_table *ht, struct qreg reg)
+{
+        struct hash_entry *entry;
+        void *key = (void *)(uintptr_t)reg.index;
+
+        entry = _mesa_hash_table_search(ht, key);
+        assert(entry);
+        entry->data--;
+        if (entry->data == NULL)
+                _mesa_hash_table_remove(ht, entry);
+}
+
+static bool
+is_lowerable_uniform(struct qinst *inst, int i)
+{
+        if (inst->src[i].file != QFILE_UNIF)
+                return false;
+        if (qir_is_tex(inst))
+                return i != 1;
+        return true;
+}
+
+void
+qir_lower_uniforms(struct vc4_compile *c)
+{
+        struct simple_node *node;
+        struct hash_table *ht =
+                _mesa_hash_table_create(c, index_hash, index_compare);
+
+        /* Walk the instruction list, finding which instructions have more
+         * than one uniform referenced, and add those uniform values to the
+         * ht.
+         */
+        foreach(node, &c->instructions) {
+                struct qinst *inst = (struct qinst *)node;
+                uint32_t nsrc = qir_get_op_nsrc(inst->op);
+
+                uint32_t count = 0;
+                for (int i = 0; i < nsrc; i++) {
+                        if (inst->src[i].file == QFILE_UNIF)
+                                count++;
+                }
+
+                if (count <= 1)
+                        continue;
+
+                for (int i = 0; i < nsrc; i++) {
+                        if (is_lowerable_uniform(inst, i))
+                                add_uniform(ht, inst->src[i]);
+                }
+        }
+
+        while (ht->entries) {
+                /* Find the most commonly used uniform in instructions that
+                 * need a uniform lowered.
+                 */
+                uint32_t max_count = 0;
+                uint32_t max_index = 0;
+                struct hash_entry *entry;
+                hash_table_foreach(ht, entry) {
+                        uint32_t count = (uintptr_t)entry->data;
+                        uint32_t index = (uintptr_t)entry->key;
+                        if (count > max_count) {
+                                max_count = count;
+                                max_index = index;
+                        }
+                }
+
+                /* Now, find the instructions using this uniform and make them
+                 * reference a temp instead.
+                 */
+                struct qreg temp = qir_get_temp(c);
+                struct qreg unif = { QFILE_UNIF, max_index };
+                struct qinst *mov = qir_inst(QOP_MOV, temp, unif, c->undef);
+                insert_at_head(&c->instructions, &mov->link);
+                foreach(node, &c->instructions) {
+                        struct qinst *inst = (struct qinst *)node;
+                        uint32_t nsrc = qir_get_op_nsrc(inst->op);
+
+                        uint32_t count = 0;
+                        for (int i = 0; i < nsrc; i++) {
+                                if (inst->src[i].file == QFILE_UNIF)
+                                        count++;
+                        }
+
+                        if (count <= 1)
+                                continue;
+
+                        for (int i = 0; i < nsrc; i++) {
+                                if (is_lowerable_uniform(inst, i) &&
+                                    inst->src[i].index == max_index) {
+                                        inst->src[i] = temp;
+                                        remove_uniform(ht, unif);
+                                        count--;
+                                }
+                        }
+
+                        /* If the instruction doesn't need lowering any more,
+                         * then drop it from the list.
+                         */
+                        if (count <= 1) {
+                                for (int i = 0; i < nsrc; i++) {
+                                        if (is_lowerable_uniform(inst, i))
+                                                remove_uniform(ht, inst->src[i]);
+                                }
+                        }
+                }
+        }
+
+        _mesa_hash_table_destroy(ht, NULL);
+}