Register decode output in a new porch stage

2 files changed, 100 insertions, 0 deletions

diff --git a/rtl/core/porch/conds.sv b/rtl/core/porch/conds.sv
new file mode 100644
index 0000000..b8db1e7
--- /dev/null
+++ b/rtl/core/porch/conds.sv
@@ -0,0 +1,47 @@
+`include "core/decode/isa.sv"
+`include "core/uarch.sv"
+
+module core_porch_conds
+(
+	input  word       insn,
+	input  psr_flags  flags,
+
+	output logic      execute,
+	                  conditional,
+	                  undefined
+);
+
+	always_comb begin
+		undefined = 0;
+		conditional = 1;
+
+		unique case(insn `FIELD_COND)
+			`COND_EQ: execute =  flags.z;
+			`COND_NE: execute = ~flags.z;
+			`COND_HS: execute =  flags.c;
+			`COND_LO: execute = ~flags.c;
+			`COND_MI: execute =  flags.n;
+			`COND_PL: execute = ~flags.n;
+			`COND_VS: execute =  flags.v;
+			`COND_VC: execute = ~flags.v;
+			`COND_HI: execute =  flags.c  & ~flags.z;
+			`COND_LS: execute = ~flags.c  |  flags.z;
+			`COND_GE: execute =  flags.n ~^  flags.v;
+			`COND_LT: execute =  flags.n  ^  flags.v;
+			`COND_GT: execute = ~flags.z  & (flags.n ~^ flags.v);
+			`COND_LE: execute =  flags.z  | (flags.n  ^ flags.v);
+
+			`COND_AL: begin
+				execute = 1;
+				conditional = 0;
+			end
+
+			`COND_UD: begin
+				execute = 1'bx;
+				conditional = 1'bx;
+				undefined = 1;
+			end
+		endcase
+	end
+
+endmodule
diff --git a/rtl/core/porch/porch.sv b/rtl/core/porch/porch.sv
new file mode 100644
index 0000000..6f5caf7
--- /dev/null
+++ b/rtl/core/porch/porch.sv
@@ -0,0 +1,53 @@
+`include "core/uarch.sv"
+
+module core_porch
+(
+	input  logic       clk,
+	                   flush,
+	                   stall,
+	input  psr_flags   flags,
+
+	input  word        fetch_insn,
+	input  ptr         fetch_insn_pc,
+	input  insn_decode fetch_dec,
+
+	output word        insn,
+	output ptr         insn_pc,
+	output insn_decode dec
+);
+
+	logic execute, conditional, undefined;
+	insn_decode nop, hold_dec;
+
+	core_porch_conds conds
+	(
+		.*
+	);
+
+	assign nop.ctrl.execute = 0;
+	assign nop.ctrl.undefined = 0;
+	assign nop.ctrl.conditional = 0;
+
+	always_comb begin
+		dec = hold_dec;
+		dec.ctrl.execute = !flush && dec.ctrl.execute && execute;
+		dec.ctrl.undefined = !flush && (dec.ctrl.undefined || undefined);
+		dec.ctrl.conditional = !flush && (dec.ctrl.conditional || conditional);
+	end
+
+	always @(posedge clk)
+		if(!stall) begin
+			insn <= fetch_insn;
+			hold_dec <= fetch_dec;
+
+			if(!flush)
+				insn_pc <= fetch_insn_pc;
+		end
+
+	initial begin
+		insn = `NOP;
+		insn_pc = 0;
+		hold_dec = nop;
+	end
+
+endmodule