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ice40: Bitstream gen for LUT permutation

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Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah 2018-08-04 18:08:07 +02:00
parent 8aaf845670
commit 67347573c2
1 changed files with 78 additions and 8 deletions
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86
ice40/bitstream.cc
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@ -229,6 +229,24 @@ static BelPin get_one_bel_pin(const Context *ctx, WireId wire)
return *pins.begin();
}
// Permute LUT init value given map (LUT input -> ext input)
unsigned permute_lut(unsigned orig_init, const std::unordered_map<int, int> &input_permute) {
unsigned new_init = 0;
for (int i = 0; i < 16; i++) {
int permute_address = 0;
for (int j = 0; j < 4; j++) {
if ((i >> j) & 0x1)
permute_address |= (1 << input_permute.at(j));
}
if ((orig_init >> i) & 0x1) {
new_init |= (1 << permute_address);
}
}
return new_init;
}
void write_asc(const Context *ctx, std::ostream &out)
{
@ -282,22 +300,33 @@ void write_asc(const Context *ctx, std::ostream &out)
BelId sw_bel;
sw_bel.index = sw_bel_idx;
NPNR_ASSERT(ctx->getBelType(sw_bel) == TYPE_ICESTORM_LC);
BelPin input = get_one_bel_pin(ctx, ctx->getPipSrcWire(pip));
if (ci.wire_data[ctx->getPipDstWire(pip).index].type == WireInfoPOD::WIRE_TYPE_LUTFF_IN_LUT)
continue; // Permutation pips
BelPin output = get_one_bel_pin(ctx, ctx->getPipDstWire(pip));
NPNR_ASSERT(input.bel == sw_bel);
NPNR_ASSERT(output.bel == sw_bel && output.pin == PIN_O);
unsigned lut_init;
switch (input.pin) {
case PIN_I0:
WireId permWire;
for (auto permPip : ctx->getPipsUphill(ctx->getPipSrcWire(pip))) {
if (ctx->getBoundPipNet(permPip) != IdString()) {
permWire = ctx->getPipSrcWire(permPip);
}
}
NPNR_ASSERT(permWire != WireId());
std::string dName = ci.wire_data[permWire.index].name.get();
switch (dName.back()) {
case '0':
lut_init = 2;
break;
case PIN_I1:
case '1':
lut_init = 4;
break;
case PIN_I2:
case '2':
lut_init = 16;
break;
case PIN_I3:
case '3':
lut_init = 256;
break;
default:
@ -345,8 +374,49 @@ void write_asc(const Context *ctx, std::ostream &out)
bool set_noreset = get_param_or_def(cell.second.get(), ctx->id("SET_NORESET"));
bool carry_enable = get_param_or_def(cell.second.get(), ctx->id("CARRY_ENABLE"));
std::vector<bool> lc(20, false);
// From arachne-pnr
// Discover permutation
std::unordered_map<int, int> input_perm;
std::set<int> unused;
for (int i = 0; i < 4; i++)
unused.insert(i);
for (int i = 0; i < 4; i++) {
WireId lut_wire = ctx->getBelPinWire(bel, PortPin(PIN_I0+i));
for (auto pip : ctx->getPipsUphill(lut_wire)) {
if (ctx->getBoundPipNet(pip) != IdString()) {
std::string name = ci.wire_data[ctx->getPipSrcWire(pip).index].name.get();
switch(name.back()) {
case '0':
input_perm[i] = 0;
unused.erase(0);
break;
case '1':
input_perm[i] = 1;
unused.erase(1);
break;
case '2':
input_perm[i] = 2;
unused.erase(2);
break;
case '3':
input_perm[i] = 3;
unused.erase(3);
break;
default:
NPNR_ASSERT_FALSE("failed to determine LUT permutation");
}
break;
}
}
}
for (int i = 0; i < 4; i++) {
if (!input_perm.count(i)) {
NPNR_ASSERT(!unused.empty());
input_perm[i] = *(unused.begin());
unused.erase(input_perm[i]);
}
}
lut_init = permute_lut(lut_init, input_perm);
for (int i = 0; i < 16; i++) {
if ((lut_init >> i) & 0x1)
lc.at(lut_perm.at(i)) = true;