Our techmap rules for $shift and $shiftx cells contained a special path
that aimed to decompose the shift LSB-first instead of MSB-first in
select cases that come up in pmux lowering. This path was needlessly
overcomplicated and contained bugs.
Instead of doing that, just switch over the main path to iterate
LSB-first (except for the specially-handled MSB for signed shifts
and overflow handling). This also makes the code consistent with
shl/shr/sshl/sshr cells, which are already decomposed LSB-first.
Fixes#2346.
The main part is converting ice40_dsp to recognize the new FF types
created in opt_dff instead of trying to recognize the mux patterns on
its own.
The fsm call has been moved upwards because the passes cannot deal with
$dffe/$sdff*, and other optimizations don't help it much anyway.
The main part is converting xilinx_dsp to recognize the new FF types
created in opt_dff instead of trying to recognize the patterns on its
own.
The fsm call has been moved upwards because the passes cannot deal with
$dffe/$sdff*, and other optimizations don't help it much anyway.
The symbiflow-arch-defs tool chain no longer needs the EXPLICIT_CARRY
within yosys itself.
Signed-off-by: Keith Rothman <537074+litghost@users.noreply.github.com>
Of standard yosys cells, xilinx_srl only works on $_DFF_?_ and
$_DFFE_?P_, which get upgraded to $_SDFFE_?P?P_ by dfflegalize at the
point where xilinx_srl is called for non-abc9. Fix this by running
ff_map.v first, resulting in FDRE cells, which are handled correctly.
The new types include:
- FFs with async reset and enable (`$adffe`, `$_DFFE_[NP][NP][01][NP]_`)
- FFs with sync reset (`$sdff`, `$_SDFF_[NP][NP][01]_`)
- FFs with sync reset and enable, reset priority (`$sdffs`, `$_SDFFE_[NP][NP][01][NP]_`)
- FFs with sync reset and enable, enable priority (`$sdffce`, `$_SDFFCE_[NP][NP][01][NP]_`)
- FFs with async reset, set, and enable (`$dffsre`, `$_DFFSRE_[NP][NP][NP][NP]_`)
- latches with reset or set (`$adlatch`, `$_DLATCH_[NP][NP][01]_`)
The new FF types are not actually used anywhere yet (this is left
for future commits).
