freedreno/ir3: add Sethi–Ullman numbering pass

Signed-off-by: Rob Clark <[email protected]>

1 files changed, 111 insertions, 0 deletions

diff --git a/src/freedreno/ir3/ir3_sun.c b/src/freedreno/ir3/ir3_sun.c
new file mode 100644
index 00000000000..7fea9a073e5
--- /dev/null
+++ b/src/freedreno/ir3/ir3_sun.c
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2018 Rob Clark <[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.
+ *
+ * Authors:
+ *    Rob Clark <[email protected]>
+ */
+
+
+#include "util/u_math.h"
+
+#include "ir3.h"
+
+/*
+ * A simple pass to do Sethi–Ullman numbering, as described in "Generalizations
+ * of the Sethi-Ullman algorithm for register allocation"[1].  This is used by
+ * the scheduler pass.
+ *
+ * TODO this could probably be more clever about flow control, ie. if a src
+ * is computed in multiple paths into a block, I think we should only have to
+ * consider the worst-case.
+ *
+ * [1] https://pdfs.semanticscholar.org/ae53/6010b214612c2571f483354c264b0b39c545.pdf
+ */
+
+static unsigned
+number_instr(struct ir3_instruction *instr)
+{
+	if (ir3_instr_check_mark(instr))
+		return instr->sun;
+
+	struct ir3_instruction *src;
+	const unsigned n = __ssa_src_cnt(instr);
+	unsigned a[n];
+	unsigned b[n];
+	unsigned i = 0;
+
+	/* TODO I think including false-deps in the calculation is the right
+	 * thing to do:
+	 */
+	foreach_ssa_src_n(src, n, instr) {
+		if (__is_false_dep(instr, n))
+			continue;
+		if (src->block != instr->block) {
+			a[i] = 1;
+		} else {
+			a[i] = number_instr(src);
+		}
+		b[i] = dest_regs(src);
+		i++;
+	}
+
+	/*
+	 * Rπ = max(aπ(1), bπ(1) + max(aπ(2), bπ(2) + max(..., bπ(k−1) + max(aπ(k), bπ(k)))...):
+	 */
+	unsigned last_r = 0;
+
+	for (int k = i - 1; k >= 0; k--) {
+		unsigned r = MAX2(a[k], b[k] + last_r);
+
+		if (k > 0)
+			r += b[k-1];
+
+		last_r = r;
+	}
+
+	last_r = MAX2(last_r, dest_regs(instr));
+
+	instr->sun = last_r;
+
+	return instr->sun;
+}
+
+void
+ir3_sun(struct ir3 *ir)
+{
+	unsigned max = 0;
+
+	ir3_clear_mark(ir);
+
+	for (unsigned i = 0; i < ir->noutputs; i++)
+		if (ir->outputs[i])
+			max = MAX2(max, number_instr(ir->outputs[i]));
+
+	list_for_each_entry (struct ir3_block, block, &ir->block_list, node) {
+		for (unsigned i = 0; i < block->keeps_count; i++)
+			max = MAX2(max, number_instr(block->keeps[i]));
+		if (block->condition)
+			max = MAX2(max, number_instr(block->condition));
+	}
+
+	ir->max_sun = max;
+}