diff options
Diffstat (limited to 'techlibs')
| -rw-r--r-- | techlibs/common/simlib.v | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/techlibs/common/simlib.v b/techlibs/common/simlib.v index 09ffa9a68..61215f59e 100644 --- a/techlibs/common/simlib.v +++ b/techlibs/common/simlib.v @@ -492,8 +492,11 @@ generate end endgenerate +// this is 'x' if Y and CO should be all 'x', and '0' otherwise +wire y_co_undef = ^{A, A, B, B, CI, CI, BI, BI}; + assign X = AA ^ BB; -assign Y = AA + BB + CI; +assign Y = (AA + BB + CI) ^ {Y_WIDTH{y_co_undef}}; function get_carry; input a, b, c; @@ -502,9 +505,9 @@ endfunction genvar i; generate - assign CO[0] = get_carry(AA[0], BB[0], CI); + assign CO[0] = get_carry(AA[0], BB[0], CI) ^ y_co_undef; for (i = 1; i < Y_WIDTH; i = i+1) begin:BLOCK3 - assign CO[i] = get_carry(AA[i], BB[i], CO[i-1]); + assign CO[i] = get_carry(AA[i], BB[i], CO[i-1]) ^ y_co_undef; end endgenerate |