From e9c2c1b7175604acd4285800c441c4bd1d676f9d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marcelina=20Ko=C5=9Bcielnicka?= Date: Mon, 6 Jul 2020 22:52:05 +0200 Subject: 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. --- passes/techmap/dfflegalize.cc | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'passes/techmap') 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 -- cgit v1.2.3