148 lines
5.1 KiB
Scala
148 lines
5.1 KiB
Scala
package Top {
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import Chisel._
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import Node._;
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import Constants._;
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class ioDivider(width: Int) extends Bundle {
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// requests
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val div_val = Bool('input);
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val div_rdy = Bool('output);
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val div_fn = UFix(4, 'input);
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val div_waddr = UFix(5, 'input);
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val dpath_rs1 = Bits(width, 'input);
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val dpath_rs2 = Bits(width, 'input);
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// responses
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val div_result_bits = Bits(width, 'output);
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val div_result_tag = UFix(5, 'output);
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val div_result_val = Bool('output);
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val div_result_rdy = Bool('input);
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}
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// class ioDivider extends Bundle {
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// // requests
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// val req_val = Bool('input);
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// val req_rdy = Bool('output);
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// val req_fn = UFix(3, 'input);
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// val req_tag = UFix(5, 'input);
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// val req_rs1 = Bits(64, 'input);
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// val req_rs2 = Bits(64, 'input);
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// // responses
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// val resp_val = Bool('output);
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// val resp_data = Bits(64, 'output);
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// val resp_tag = UFix(5, 'output);
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// }
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class rocketDivider(width : Int) extends Component {
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val io = new ioDivider(width);
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val s_ready :: s_neg_inputs :: s_busy :: s_neg_outputs :: s_done :: Nil = Enum(5) { UFix() };
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val state = Reg(resetVal = s_ready);
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val count_bits = java.math.BigInteger.valueOf(width).bitLength();
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val count = Reg(resetVal = UFix(0, count_bits));
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val divby0 = Reg(resetVal = Bool(false));
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val neg_quo = Reg(resetVal = Bool(false));
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val neg_rem = Reg(resetVal = Bool(false));
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val reg_waddr = Reg(resetVal = UFix(0, 5));
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val rem = Reg(resetVal = Bool(false));
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val half = Reg(resetVal = Bool(false));
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val tc = Reg(resetVal = Bool(false));
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val divisor = Reg(resetVal = UFix(0, width));
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val remainder = Reg(resetVal = UFix(0, 2*width+1));
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val subtractor = remainder(2*width, width).toUFix - divisor;
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val v_tc = ((io.div_fn === DIV_64D) || (io.div_fn === DIV_64R)) ||
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((io.div_fn === DIV_32D) || (io.div_fn === DIV_32R));
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val v_rem = ((io.div_fn === DIV_32R) || (io.div_fn === DIV_32RU)) ||
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((io.div_fn === DIV_64R) || (io.div_fn === DIV_64RU));
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val v_half = ((io.div_fn === DIV_32R) || (io.div_fn === DIV_32RU)) ||
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((io.div_fn === DIV_32D) || (io.div_fn === DIV_32DU));
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// state machine
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switch (state) {
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is (s_ready) {
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when (!io.div_val) { state <== s_ready; }
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when (v_tc) { state <== s_neg_inputs };
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otherwise { state <== s_busy; }
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}
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is (s_neg_inputs) { state <== s_busy; }
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is (s_busy) {
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when (count != UFix(width)) { state <== s_busy; }
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when (!(neg_quo || neg_rem)) { state <== s_done; }
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otherwise { state <== s_neg_outputs; }
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}
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is (s_neg_outputs) { state <== s_done; }
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is (s_done) {
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when (io.div_result_rdy) { state <== s_ready; }
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}
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}
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// if we're doing 32-bit unsigned division, then we don't want the 32-bit
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// inputs to be sign-extended.
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val in_lhs = Mux((v_half && !v_tc),
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Cat(Fill(width/2, UFix(0,1)), io.dpath_rs1(width/2-1, 0)),
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io.dpath_rs1).toUFix;
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val in_rhs = Mux((v_half && !v_tc),
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Cat(Fill(width/2, UFix(0,1)), io.dpath_rs2(width/2-1, 0)),
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io.dpath_rs2).toUFix;
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when ((state === s_ready) && io.div_val) {
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count <== UFix(0, count_bits);
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half <== v_half;
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neg_quo <== Bool(false);
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neg_rem <== Bool(false);
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rem <== v_rem;
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tc <== v_tc;
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reg_waddr <== io.div_waddr;
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divby0 <== Bool(true);
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divisor <== in_rhs;
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remainder <== Cat(Fill(width+1, UFix(0,1)), in_lhs).toUFix;
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}
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when (state === s_neg_inputs) {
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neg_rem <== remainder(width-1).toBool;
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neg_quo <== (remainder(width-1) != divisor(width-1));
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when (remainder(width-1).toBool) {
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remainder <== Cat(remainder(2*width, width), -remainder(width-1,0)).toUFix;
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}
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when (divisor(width-1).toBool) {
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divisor <== subtractor(width-1,0);
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}
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}
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when (state === s_neg_outputs) {
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when (neg_rem && neg_quo && !divby0) {
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remainder <== Cat(-remainder(2*width, width+1), remainder(width), -remainder(width-1,0)).toUFix;
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}
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when (neg_quo && !divby0) {
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remainder <== Cat(remainder(2*width, width), -remainder(width-1,0)).toUFix;
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}
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when (neg_rem) {
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remainder <== Cat(-remainder(2*width, width+1), remainder(width,0)).toUFix;
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}
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when (divisor(width-1).toBool) {
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divisor <== subtractor(width-1,0);
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}
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}
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when (state === s_busy) {
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count <== count + UFix(1);
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divby0 <== divby0 && !subtractor(width).toBool;
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remainder <== Mux(subtractor(width).toBool,
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Cat(remainder(2*width-1, width), remainder(width-1,0), ~subtractor(width)),
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Cat(subtractor(width-1, 0), remainder(width-1,0), ~subtractor(width))).toUFix;
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}
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val result = Mux(rem, remainder(2*width, width+1), remainder(width-1,0));
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io.div_result_bits := Mux(half, Cat(Fill(width/2, result(width/2-1)), result(width/2-1,0)), result);
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io.div_rdy := (state === s_ready);
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io.div_result_tag := reg_waddr;
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io.div_result_val := (state === s_done);
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}
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}
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