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Consistent $mux undef handling

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* Change simlib's $mux cell to use the ternary operator as $_MUX_
  already does
* Stop opt_expr -keepdc from changing S=x to S=0
* Change const eval of $mux and $pmux to match the updated simlib
  (fixes sim)
* The sat behavior of $mux already matches the updated simlib

The verilog frontend uses $mux for the ternary operators and this
changes all interpreations of the $mux cell (that I found) to match the
verilog simulation behavior for the ternary operator. For 'if' and
'case' expressions the frontend may also use $mux but uses $eqx if the
verilog simulation behavior is requested with the '-ifx' option.

For $pmux there is a remaining mismatch between the sat behavior and the
simlib behavior. Resolving this requires more discussion, as the $pmux
cell does not directly correspond to a specific verilog construct.
This commit is contained in:
Jannis Harder 2022-10-21 15:41:20 +02:00
parent 4f4cff0080
commit c77b7343d0
5 changed files with 38 additions and 15 deletions
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2
kernel/rtlil.h
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@ -500,6 +500,8 @@ namespace RTLIL
RTLIL::Const const_pos (const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len);
RTLIL::Const const_neg (const RTLIL::Const &arg1, const RTLIL::Const &arg2, bool signed1, bool signed2, int result_len);
RTLIL::Const const_mux (const RTLIL::Const &arg1, const RTLIL::Const &arg2, const RTLIL::Const &arg3);
RTLIL::Const const_pmux (const RTLIL::Const &arg1, const RTLIL::Const &arg2, const RTLIL::Const &arg3);
RTLIL::Const const_bmux (const RTLIL::Const &arg1, const RTLIL::Const &arg2);
RTLIL::Const const_demux (const RTLIL::Const &arg1, const RTLIL::Const &arg2);