Implement ALU shifter

1 files changed, 28 insertions, 5 deletions

diff --git a/rtl/core/alu/shifter.sv b/rtl/core/alu/shifter.sv
index 3effb2c..4385b41 100644
--- a/rtl/core/alu/shifter.sv
+++ b/rtl/core/alu/shifter.sv
@@ -1,12 +1,35 @@
-module alu_shl
+`include "core/uarch.sv"
+
+module core_alu_shifter
 #(parameter W=16)
 (
-	input  logic[W - 1:0] a,
-	                      b,
-	output logic[W - 1:0] q,
+	input  alu_control    ctrl,
+	input  logic[W - 1:0] base,
+	input  logic[7:0]     shift,
+	input  logic          c_in,
+
+	output logic[W - 1:0] b,
 	output logic          c
 );
 
-	assign {c, q} = {1'b0, a} << b;
+	logic [W - 1:0] b_no_c, b_shl, b_shr, b_ror;
+	logic [W:0] sign_mask;
+	logic c_shl, c_shr;
+
+	assign sign_mask = {(W + 1){ctrl.sign_extend & base[W - 1]}};
+	assign {c_shl, b_shl} = {c_in, base} << shift;
+	assign {b_shr, c_shr} = {base, c_in} >> shift | ~(sign_mask >> shift);
+	assign b_ror = b_shr | base << (W - shift);
+
+	assign b = {b_no_c[W - 1] | (ctrl.put_carry & c_in), b_no_c[W - 2:0]};
+	assign c = ctrl.shr | ctrl.ror ? c_shr : c_shl;
+
+	always_comb
+		if(ctrl.ror)
+			b = b_ror;
+		else if(ctrl.shr)
+			b = {b_shr[W - 1] | (ctrl.put_carry & c_in), b_shr[W - 2:0]};
+		else
+			b = b_shl;
 
 endmodule