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`include "core/isa.sv"
`include "core/uarch.sv"
module core_decode_snd
(
input word insn,
input logic is_imm,
ror_if_imm,
shift_by_reg_if_reg,
output snd_decode decode,
output logic undefined
);
reg_num r, r_shift;
logic shift_by_reg, shl, shr, ror, put_carry, sign_extend;
logic[11:0] imm;
logic[5:0] shift_imm;
assign decode.r = r;
assign decode.r_shift = r_shift;
assign decode.shift_by_reg = shift_by_reg;
assign decode.is_imm = is_imm;
assign decode.shl = shl;
assign decode.shr = shr;
assign decode.ror = ror;
assign decode.put_carry = put_carry;
assign decode.sign_extend = sign_extend;
assign decode.imm = imm;
assign decode.shift_imm = shift_imm;
assign r = insn `FIELD_SND_RM;
assign r_shift = insn `FIELD_SND_RS;
assign imm = ror_if_imm ? {4'b0, insn `FIELD_SND_IMM8} : insn `FIELD_SND_IMM12;
assign shift_by_reg = ~is_imm & shift_by_reg_if_reg;
assign undefined = shift_by_reg & insn `FIELD_SND_ZEROIFREG;
logic[1:0] shift_op;
assign shift_op = insn `FIELD_SND_SHIFT;
always_comb begin
ror = is_imm;
shr = ~is_imm;
put_carry = 0;
sign_extend = 1'bx;
if(is_imm && !ror_if_imm)
shift_imm = 6'b0;
else if(is_imm && !ror_if_imm)
shift_imm = {1'b0, insn `FIELD_SND_ROR8, 1'b0};
else begin
shift_imm = {1'b0, insn `FIELD_SND_SHIFTIMM};
case(shift_op)
`SHIFT_LSL: shr = 0;
`SHIFT_LSR: sign_extend = 0;
`SHIFT_ASR: sign_extend = 1;
`SHIFT_ROR: ;
endcase
if(~shift_by_reg & (shift_imm == 0))
case(shift_op)
`SHIFT_LSL: ;
`SHIFT_LSR, `SHIFT_ASR:
shift_imm = 6'd32;
`SHIFT_ROR: begin
// RRX
shift_imm = 6'd1;
put_carry = 1;
sign_extend = 0;
end
endcase
else if(shift_op == `SHIFT_ROR)
ror = 1;
end
end
endmodule
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