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| author | Marcelina Kościelnicka <mwk@0x04.net> | 2020-07-06 22:52:05 +0200 |
|---|---|---|
| committer | Marcelina Kościelnicka <mwk@0x04.net> | 2020-07-09 18:11:32 +0200 |
| commit | e9c2c1b7175604acd4285800c441c4bd1d676f9d (patch) | |
| tree | df38b8d83094977f6adff764cfd166210da639ad /passes | |
| parent | 000fd08198487cd1d36e65e4470f4b0269c23a2b (diff) | |
| download | yosys-e9c2c1b7175604acd4285800c441c4bd1d676f9d.tar.gz yosys-e9c2c1b7175604acd4285800c441c4bd1d676f9d.tar.bz2 yosys-e9c2c1b7175604acd4285800c441c4bd1d676f9d.zip | |
dfflegalize: Add special support for const-D latches.
Those can be created by `opt_dff` when optimizing `$adff` with const
clock, or with D == Q. Make dfflegalize do the opposite transform
when such dlatches would be otherwise unimplementable.
Diffstat (limited to 'passes')
| -rw-r--r-- | passes/techmap/dfflegalize.cc | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/passes/techmap/dfflegalize.cc b/passes/techmap/dfflegalize.cc index eb35d778a..c0f112836 100644 --- a/passes/techmap/dfflegalize.cc +++ b/passes/techmap/dfflegalize.cc @@ -659,6 +659,24 @@ flip_dqisr:; // This init value is not supported at all... if (supported_dlatch & flip_initmask(initmask)) goto flip_dqi; + + if ((sig_d == State::S0 && (supported_adff0 & initmask)) || + (sig_d == State::S1 && (supported_adff1 & initmask)) || + (sig_d == State::S0 && (supported_adff1 & flip_initmask(initmask))) || + (sig_d == State::S1 && (supported_adff0 & flip_initmask(initmask))) + ) { + // Special case: const-D dlatch can be converted into adff with const clock. + ff_type = (sig_d == State::S0) ? FF_ADFF0 : FF_ADFF1; + if (ff_neg & NEG_E) { + ff_neg &= ~NEG_E; + ff_neg |= NEG_R; + } + sig_r = sig_e; + sig_d = State::Sx; + sig_c = State::S1; + continue; + } + if (!supported_dlatch) reason = "dlatch are not supported"; else |