From 0141d830f3326594f159c627dbbc284fdef27674 Mon Sep 17 00:00:00 2001
From: Kimplul <kimi.h.kuparinen@gmail.com>
Date: Sat, 15 Feb 2025 21:54:16 +0200
Subject: initial scheduler

---
 src/sched.sv | 109 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 src/sched.sv

(limited to 'src/sched.sv')

diff --git a/src/sched.sv b/src/sched.sv
new file mode 100644
index 0000000..c538dc2
--- /dev/null
+++ b/src/sched.sv
@@ -0,0 +1,109 @@
+`include "common.svh"
+
+module sched
+#(
+	parameter QUE_DEPTH,
+	parameter SLOT_COUNT,
+	parameter SLOT_DEPTH,
+	type port_t,
+	type mov_t,
+	type insn_t,
+	type slot_t
+)(
+	input insn_t[QUE_DEPTH-1:0] que_i,
+	output insn_t[QUE_DEPTH-1:0] que_o,
+	input slot_t[SLOT_COUNT-1:0] slots_i,
+	output slot_t[SLOT_COUNT-1:0] slots_o
+);
+
+/* check_* don't always use whole signal they're given, so I think it's best to
+ * just silence this */
+/* verilator lint_off UNUSEDSIGNAL */
+
+function automatic insn_t[QUE_DEPTH-1:0] next_insn(insn_t[QUE_DEPTH-1:0] que);
+	return que >> $bits(insn_t);
+endfunction
+
+/* check if a write is to the same destination port */
+function automatic logic check_dst(mov_t d1, mov_t[SLOT_DEPTH-1:0] d2);
+	logic[SLOT_DEPTH-1:0] dep = '0;
+	for (int i = 0; i < SLOT_DEPTH; ++i) begin
+		dep[i] = d1.dst != `NOP & d1.dst == d2[i].dst;
+	end
+	return dep != 0;
+endfunction
+
+/* check if any read is from an output port that's not free */
+function automatic logic check_overlap(mov_t d1, mov_t[SLOT_DEPTH-1:0] d2);
+	logic[SLOT_DEPTH-1:0] dep = '0;
+	for (int i = 0; i < SLOT_DEPTH; ++i) begin
+		dep[i] = d1.src != `NOP & d1.src == d2[i].dst;
+	end
+	return dep != 0;
+endfunction
+
+/* check if instruction depends on any existing slots */
+function automatic logic depends(insn_t i, slot_t[SLOT_COUNT-1:0] slots);
+	logic[SLOT_COUNT-1:0] dep = '0;
+	for (int ii = 0; ii < SLOT_COUNT; ++ii) begin
+		logic same_dst = check_dst(i.out, slots[ii].out);
+		logic overlap1 = check_overlap(i.in[0], slots[ii].out);
+		logic overlap2 = check_overlap(i.in[1], slots[ii].out);
+
+		logic same_src1 = i.in[0].dst != `NOP
+				& i.in[0].dst == slots[ii].in[0].dst;
+
+		/* op must have trigger so don't need to check against NOP */
+		logic same_src2 = i.in[1].dst == slots[ii].in[1].dst;
+
+		dep[ii] = same_dst | overlap1 | overlap2 | same_src1 | same_src2;
+	end
+	return dep != 0;
+endfunction
+
+function automatic logic is_noop(mov_t m);
+	return m.src == `NOP && m.dst == `NOP;
+endfunction
+
+function automatic mov_t[SLOT_DEPTH-1:0] place_out(int i, logic placed,
+	mov_t o, mov_t[SLOT_DEPTH-1:0] out);
+	if (i < SLOT_DEPTH) begin
+		logic ok = !placed & is_noop(out[i]);
+		out[i] = ok ? o : out[i];
+		return place_out(i + 1, ok ? 1 : placed, o, out);
+	end else begin
+		return out;
+	end
+endfunction
+
+/* place instruction into slot */
+function automatic slot_t place(insn_t i, slot_t src);
+	slot_t slot;
+	slot.op = i.op;
+	slot.in = i.in;
+	slot.out = place_out(0, 0, i.out, src.out);
+	return slot;
+endfunction
+
+typedef struct packed {
+	insn_t[QUE_DEPTH-1:0] que;
+	slot_t[SLOT_COUNT-1:0] slots;
+} stages_out_t;
+
+function automatic stages_out_t stages(int i,
+	insn_t[QUE_DEPTH-1:0] que, slot_t[SLOT_COUNT-1:0] slots);
+	if (i < SLOT_COUNT) begin
+		logic ok = !depends(que[0], slots);
+		slots[i] = ok ? place(que[0], slots[i]) : slots[i];
+		return stages(i + 1, ok ? next_insn(que) : que, slots);
+	end else begin
+		return {que, slots};
+	end
+endfunction
+
+always_comb begin
+	stages_out_t out = stages(0, que_i, slots_i);
+	que_o = out.que;
+	slots_o = out.slots;
+end
+endmodule
-- 
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