riscv/rocket-chip
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booth multiplier

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This commit is contained in:
Andrew Waterman 2011-12-20 03:49:07 -08:00
parent b5a8b6dc73
commit 733fc8e65e
2 changed files with 49 additions and 29 deletions
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1
rocket/src/main/scala/dpath.scala
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@ -292,6 +292,7 @@ class rocketDpath extends Component
io.ctrl.mul_rdy := mul.io.mul_rdy
io.ctrl.mul_result_val := mul.io.result_val;
mul.io.result_rdy := io.ctrl.mul_wb
io.ctrl.ex_waddr := ex_reg_waddr; // for load/use hazard detection & bypass control

77
rocket/src/main/scala/multiplier.scala
View File

@ -10,63 +10,82 @@ class ioMultiplier(width: Int) extends Bundle {
val mul_rdy = Bool('output);
val dw = UFix(1, 'input);
val mul_fn = UFix(2, 'input);
val mul_tag = UFix(5, 'input);
val mul_tag = UFix(CPU_TAG_BITS, 'input);
val in0 = Bits(width, 'input);
val in1 = Bits(width, 'input);
// responses
val result = Bits(width, 'output);
val result_tag = UFix(5, 'output);
val result_tag = UFix(CPU_TAG_BITS, 'output);
val result_val = Bool('output);
val result_rdy = Bool('input);
}
class rocketMultiplier extends Component {
val io = new ioMultiplier(64);
val width = 64 + 2
val cycles = width/2
val r_val = Reg(resetVal = Bool(false));
val r_dw = Reg(resetVal = UFix(0,1));
val r_fn = Reg(resetVal = UFix(0,3));
val r_tag = Reg(resetVal = UFix(0,5));
val r_lhs = Reg(resetVal = Bits(0,65));
val r_rhs = Reg(resetVal = Bits(0,65));
val r_dw = Reg { UFix() }
val r_fn = Reg { UFix() }
val r_tag = Reg { UFix() }
val r_lhs = Reg { Bits() }
val r_prod= Reg { Bits(width = width*2) }
val r_lsb = Reg { Bits() }
val r_cnt = Reg { UFix(width = log2up(cycles+1)) }
val lhs_msb = Mux(io.dw === DW_64, io.in0(63), io.in0(31)).toBool
val lhs_sign = ((io.mul_fn === MUL_HS) || (io.mul_fn === MUL_HSU)) && lhs_msb
val lhs_hi = Mux(io.dw === DW_64, io.in0(63,32), Fill(32, lhs_sign))
val lhs = Cat(lhs_sign, lhs_hi, io.in0(31,0))
val lhs_in = Cat(lhs_sign, lhs_hi, io.in0(31,0))
val rhs_msb = Mux(io.dw === DW_64, io.in1(63), io.in1(31)).toBool
val rhs_sign = (io.mul_fn === MUL_HS) && rhs_msb
val rhs_hi = Mux(io.dw === DW_64, io.in1(63,32), Fill(32, rhs_sign))
val rhs = Cat(rhs_sign, rhs_hi, io.in1(31,0))
val rhs_in = Cat(rhs_sign, rhs_sign, rhs_hi, io.in1(31,0))
r_val <== io.mul_val;
when (io.mul_val) {
when (io.mul_val && io.mul_rdy) {
r_val <== Bool(true)
r_cnt <== UFix(0, log2up(cycles+1))
r_dw <== io.dw
r_fn <== io.mul_fn;
r_tag <== io.mul_tag;
r_lhs <== lhs;
r_rhs <== rhs;
r_fn <== io.mul_fn
r_tag <== io.mul_tag
r_lhs <== lhs_in
r_prod<== rhs_in
r_lsb <== Bool(false)
}
when (io.result_val && io.result_rdy) {
r_val <== Bool(false)
}
val mul_result = r_lhs.toFix * r_rhs.toFix;
val mul_output64 = Mux(r_fn === MUL_LO, mul_result(63,0), mul_result(127,64))
val mul_output32 = Mux(r_fn === MUL_LO, mul_result(31,0), mul_result(63,31))
val lhs_sext = Cat(r_lhs(width-2), r_lhs(width-2), r_lhs).toUFix
val lhs_twice = Cat(r_lhs(width-2), r_lhs, Bits(0,1)).toUFix
val addend = Mux(r_prod(0) != r_lsb, lhs_sext,
Mux(r_prod(0) != r_prod(1), lhs_twice,
UFix(0)));
val sub = r_prod(1)
val adder_lhs = Cat(r_prod(width*2-1), r_prod(width*2-1,width)).toUFix
val adder_rhs = Mux(sub, ~addend, addend)
val adder_out = (adder_lhs + adder_rhs + sub.toUFix)(width,0)
when (r_val && (r_cnt != UFix(cycles))) {
r_lsb <== r_prod(1)
r_prod <== Cat(adder_out(width), adder_out, r_prod(width-1,2))
r_cnt <== r_cnt + UFix(1)
}
val mul_output64 = Mux(r_fn === MUL_LO, r_prod(63,0), r_prod(127,64))
val mul_output32 = Mux(r_fn === MUL_LO, r_prod(31,0), r_prod(63,31))
val mul_output32_ext = Cat(Fill(32, mul_output32(31)), mul_output32)
val mul_output = Mux(r_dw === DW_64, mul_output64, mul_output32_ext)
// just a hack for now, this should be a parameterized number of stages
val r_result = Reg(Reg(Reg(mul_output)));
val r_result_tag = Reg(Reg(Reg(r_tag)));
val r_result_val = Reg(Reg(Reg(r_val)));
io.mul_rdy := Bool(true)
io.result := r_result;
io.result_tag := r_result_tag;
io.result_val := r_result_val;
io.mul_rdy := !r_val
io.result := mul_output;
io.result_tag := r_tag;
io.result_val := r_val && (r_cnt === UFix(cycles))
}
}