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mistral: Don't allow route-through LUTs in carry-mode ALMs

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Signed-off-by: gatecat <gatecat@ds0.me>
This commit is contained in:
gatecat 2023-05-17 10:00:09 +02:00 committed by myrtle
parent bc7b8b63ed
commit 98121308e0
2 changed files with 10 additions and 4 deletions
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1
mistral/arch.h
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@ -48,6 +48,7 @@ struct ALMInfo
std::array<BelId, 4> ff_bels;
bool l6_mode = false;
bool carry_mode = false;
// Which CLK/ENA and ACLR is chosen for each half
std::array<int, 2> clk_ena_idx, aclr_idx;

13
mistral/lab.cc
View File

@ -425,7 +425,7 @@ bool Arch::is_alm_legal(uint32_t lab, uint8_t alm) const
return false;
}
bool carry_mode = false;
bool carry_mode = (luts[0] && luts[0]->combInfo.is_carry) || (luts[1] && luts[1]->combInfo.is_carry);
// No mixing of carry and non-carry
if (luts[0] && luts[1] && luts[0]->combInfo.is_carry != luts[1]->combInfo.is_carry)
@ -811,6 +811,7 @@ void Arch::reassign_alm_inputs(uint32_t lab, uint8_t alm)
// This function should also insert route-through LUTs to legalise flipflop inputs as needed.
auto &alm_data = labs.at(lab).alms.at(alm);
alm_data.l6_mode = false;
alm_data.carry_mode = false;
std::array<CellInfo *, 2> luts{getBoundBelCell(alm_data.lut_bels[0]), getBoundBelCell(alm_data.lut_bels[1])};
std::array<CellInfo *, 4> ffs{getBoundBelCell(alm_data.ff_bels[0]), getBoundBelCell(alm_data.ff_bels[1]),
getBoundBelCell(alm_data.ff_bels[2]), getBoundBelCell(alm_data.ff_bels[3])};
@ -820,6 +821,8 @@ void Arch::reassign_alm_inputs(uint32_t lab, uint8_t alm)
// Currently we treat LUT6s and MLABs as a special case, as they never share inputs or have fixed mappings
if (!luts[i])
continue;
if (luts[i]->combInfo.is_carry)
alm_data.carry_mode = true;
if (luts[i]->type == id_MISTRAL_ALUT6) {
alm_data.l6_mode = true;
NPNR_ASSERT(luts[1 - i] == nullptr); // only allow one LUT6 per ALM and no other LUTs
@ -916,7 +919,7 @@ void Arch::reassign_alm_inputs(uint32_t lab, uint8_t alm)
continue;
for (int j = 0; j < 2; j++) {
CellInfo *ff = ffs[i * 2 + j];
if (!ff || !ff->ffInfo.datain || alm_data.l6_mode)
if (!ff || !ff->ffInfo.datain || alm_data.l6_mode || alm_data.carry_mode)
continue;
CellInfo *rt_lut = createCell(idf("%s$ROUTETHRU", nameOf(ff)), id_MISTRAL_BUF);
rt_lut->addInput(id_A);
@ -1045,10 +1048,12 @@ uint64_t Arch::compute_lut_mask(uint32_t lab, uint8_t alm)
}
}
CellPinState state = lut->get_pin_state(log_pin);
if (state == PIN_0)
if (state == PIN_0) {
continue;
else if (state == PIN_1)
} else if (state == PIN_1) {
index |= (1 << init_idx);
continue;
}
// Ignore if no associated physical pin
if (lut->getPort(log_pin) == nullptr || lut->pin_data.at(log_pin).bel_pins.empty())
continue;