1 files changed, 114 insertions, 0 deletions
diff --git a/src/panfrost/midgard/midgard_liveness.c b/src/panfrost/midgard/midgard_liveness.c
new file mode 100644
index 00000000000..a18d8b9f8ad
--- /dev/null
+++ b/src/panfrost/midgard/midgard_liveness.c
@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2018-2019 Alyssa Rosenzweig <[email protected]>
+ *
+ * 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.
+ */
+
+/* mir_is_live_after performs liveness analysis on the MIR, used primarily
+ * as part of register allocation. TODO: Algorithmic improvements for
+ * compiler performance (this is the worst algorithm possible -- see
+ * backlog with Connor on IRC) */
+
+#include "compiler.h"
+
+static bool
+midgard_is_live_in_instr(midgard_instruction *ins, int src)
+{
+        if (ins->compact_branch)
+                return false;
+
+        if (ins->ssa_args.src0 == src)
+                return true;
+
+        if (!ins->ssa_args.inline_constant && ins->ssa_args.src1 == src)
+                return true;
+
+        return false;
+}
+
+/* Determine if a variable is live in the successors of a block */
+static bool
+is_live_after_successors(compiler_context *ctx, midgard_block *bl, int src)
+{
+        for (unsigned i = 0; i < bl->nr_successors; ++i) {
+                midgard_block *succ = bl->successors[i];
+
+                /* If we already visited, the value we're seeking
+                 * isn't down this path (or we would have short
+                 * circuited */
+
+                if (succ->visited) continue;
+
+                /* Otherwise (it's visited *now*), check the block */
+
+                succ->visited = true;
+
+                mir_foreach_instr_in_block(succ, ins) {
+                        if (midgard_is_live_in_instr(ins, src))
+                                return true;
+                }
+
+                /* ...and also, check *its* successors */
+                if (is_live_after_successors(ctx, succ, src))
+                        return true;
+
+        }
+
+        /* Welp. We're really not live. */
+
+        return false;
+}
+
+bool
+mir_is_live_after(compiler_context *ctx, midgard_block *block, midgard_instruction *start, int src)
+{
+        /* Check the rest of the block for liveness */
+
+        mir_foreach_instr_in_block_from(block, ins, mir_next_op(start)) {
+                if (midgard_is_live_in_instr(ins, src))
+                        return true;
+        }
+
+        /* Check the rest of the blocks for liveness recursively */
+
+        bool succ = is_live_after_successors(ctx, block, src);
+
+        mir_foreach_block(ctx, block) {
+                block->visited = false;
+        }
+
+        return succ;
+}
+
+/* Just a quick check -- is it written more than once? (I.e. are we definitely
+ * not SSA?) */
+
+bool
+mir_has_multiple_writes(compiler_context *ctx, int dest)
+{
+        unsigned write_count = 0;
+
+        mir_foreach_instr_global(ctx, ins) {
+                if (ins->ssa_args.dest == dest)
+                        write_count++;
+        }
+
+        return write_count > 1;
+}