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cyclonev: First (untested) pass at ALM validity checking

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Signed-off-by: gatecat <gatecat@ds0.me>
This commit is contained in:
gatecat 2021-05-04 21:23:11 +01:00
parent 1cd22b81da
commit fbdcfa9c42
2 changed files with 135 additions and 40 deletions
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6
cyclonev/arch.cc
View File

@ -210,7 +210,8 @@ std::vector<IdString> Arch::getBelPins(BelId bel) const
return pins;
}
bool Arch::isValidBelForCellType(IdString cell_type, BelId bel) const {
bool Arch::isValidBelForCellType(IdString cell_type, BelId bel) const
{
// Any combinational cell type can - theoretically - be placed at a combinational ALM bel
// The precise legality mechanics will be dealt with in isBelLocationValid.
IdString bel_type = getBelType(bel);
@ -220,7 +221,8 @@ bool Arch::isValidBelForCellType(IdString cell_type, BelId bel) const {
return bel_type == cell_type;
}
BelBucketId Arch::getBelBucketForCellType(IdString cell_type) const {
BelBucketId Arch::getBelBucketForCellType(IdString cell_type) const
{
if (is_comb_cell(cell_type))
return id_MISTRAL_COMB;
else

97
cyclonev/lab.cc
View File

@ -190,7 +190,8 @@ void Arch::create_lab(int x, int y)
// Cell handling and annotation functions
namespace {
ControlSig get_ctrlsig(const CellInfo *cell, IdString port) {
ControlSig get_ctrlsig(const CellInfo *cell, IdString port)
{
ControlSig result;
result.net = get_net_or_empty(cell, port);
if (cell->pin_data.count(port))
@ -199,7 +200,7 @@ namespace {
result.inverted = false;
return result;
}
}
} // namespace
bool Arch::is_comb_cell(IdString cell_type) const
{
@ -284,4 +285,96 @@ void Arch::assign_ff_info(CellInfo *cell) const
cell->ffInfo.datain = get_net_or_empty(cell, id_DATAIN);
}
// Validity checking functions
bool Arch::is_alm_legal(uint32_t lab, uint8_t alm) const
{
auto &alm_data = labs.at(lab).alms.at(alm);
// Get cells into an array for fast access
std::array<const CellInfo *, 2> luts{getBoundBelCell(alm_data.lut_bels[0]), getBoundBelCell(alm_data.lut_bels[1])};
std::array<const 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])};
int used_lut_bits = 0;
int total_lut_inputs = 0;
// TODO: for more complex modes like extended/arithmetic, it might not always be possible for any LUT input to map
// to any of the ALM half inputs particularly shared and extended mode will need more thought and probably for this
// to be revisited
for (int i = 0; i < 2; i++) {
if (!luts[i])
continue;
total_lut_inputs += luts[i]->combInfo.lut_input_count;
used_lut_bits += luts[i]->combInfo.lut_bits_count;
}
// An ALM only has 64 bits of storage. In theory some of these cases might be legal because of overlap between the
// two functions, but the current placer is unlikely to stumble upon these cases frequently without anything to
// guide it, and the cost of checking them here almost certainly outweighs any marginal benefit in supporting them,
// at least for now.
if (used_lut_bits > 64)
return false;
if (total_lut_inputs > 8) {
NPNR_ASSERT(luts[0] && luts[1]); // something has gone badly wrong if this fails!
// Make sure that LUT inputs are not overprovisioned
int shared_lut_inputs = 0;
// Even though this N^2 search looks inefficient, it's unlikely a set lookup or similar is going to be much
// better given the low N.
for (int i = 0; i < luts[1]->combInfo.lut_input_count; i++) {
const NetInfo *sig = luts[1]->combInfo.lut_in[i];
for (int j = 0; j < luts[0]->combInfo.lut_input_count; j++) {
if (sig == luts[0]->combInfo.lut_in[j]) {
++shared_lut_inputs;
break;
}
}
}
if ((total_lut_inputs - shared_lut_inputs) > 8)
return false;
}
// For each ALM half; check FF control set sharing and input routeability
for (int i = 0; i < 2; i++) {
// There are two ways to route from the fabric into FF data - either routing through a LUT or using the E/F
// signals and SLOAD=1 (*PKREF*)
bool route_thru_lut_avail = !luts[i] && (total_lut_inputs < 8) && (used_lut_bits < 64);
// E/F is available if the LUT is using less than 6 inputs - TODO: is this correct considering all possible LUT
// sharing
bool ef_available = (!luts[i] || luts[i]->combInfo.lut_input_count < 6);
// Control set checking
bool found_ff = false;
FFControlSet ctrlset;
for (int j = 0; j < 2; j++) {
const CellInfo *ff = ffs[i * 2 + j];
if (!ff)
continue;
if (found_ff) {
// Two FFs in the same half with an incompatible control set
if (ctrlset != ff->ffInfo.ctrlset)
return false;
} else {
ctrlset = ff->ffInfo.ctrlset;
}
// SDATA must use the E/F input
// TODO: rare case of two FFs with the same SDATA in the same ALM half
if (ff->ffInfo.sdata) {
if (!ef_available)
return false;
ef_available = false;
}
// Find a way of routing the input through fabric, if it's not driven by the LUT
if (ff->ffInfo.datain && (!luts[i] || (ff->ffInfo.datain != luts[i]->combInfo.comb_out))) {
if (route_thru_lut_avail)
route_thru_lut_avail = false;
else if (ef_available)
ef_available = false;
else
return false;
}
found_ff = true;
}
}
return true;
}
NEXTPNR_NAMESPACE_END