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Legalizer for Part misses one branch #52

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rroohhh opened this issue Mar 26, 2019 · 1 comment
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Legalizer for Part misses one branch #52

rroohhh opened this issue Mar 26, 2019 · 1 comment
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bug
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0.1

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@rroohhh
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rroohhh commented Mar 26, 2019 •
edited

Shouldn't this line read:

raise LegalizeValue(value.offset, range(1 << len(value.offset)))

Currently this:

from nmigen import *
from nmigen.cli import main

m = Module()

p = Signal(4, reset=0b11)
a = Signal(1, reset = 1)

m.d.sync += p.part(a, 1).eq(0)

if __name__ == "__main__":
    main(m)

just generates one assignment:

/* Generated by Yosys 0.8+152 (git sha1 2a8e5bf9, gcc 8.2.0-r6 -fPIC -O3) */

(* top =  1  *)
(* generator = "nMigen" *)
module top(rst, clk, a);
  (* src = "cdc.py:6" *)
  reg [3:0] \$next\p ;
  (* src = "cdc.py:7" *)
  input a;
  (* src = "/home/robin/.local/lib/python3.7/site-packages/nmigen/hdl/ir.py:304" *)
  input clk;
  (* init = 4'h3 *)
  (* src = "cdc.py:6" *)
  reg [3:0] p = 4'h3;
  (* src = "/home/robin/.local/lib/python3.7/site-packages/nmigen/hdl/ir.py:304" *)
  input rst;
  always @(posedge clk)
      p <= \$next\p ;
  always @* begin
    \$next\p  = p;
    casez (a)
      1'hz:
          \$next\p [0] = 1'h0;
    endcase
    casez (rst)
      1'h1:
          \$next\p  = 4'h3;
    endcase
  end
endmodule

which does not seem equivalent to the described logic.
@rroohhh rroohhh mentioned this issue Mar 26, 2019
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@whitequark whitequark added the bug label Mar 27, 2019
@whitequark
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You're right! Good catch.

@whitequark whitequark added this to the 0.1 milestone Jun 28, 2019
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