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ecp5: Function to handle constant LUT inputs

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Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah 2018-07-17 21:51:24 +02:00
parent ddfc535df7
commit edf7bd09cf
1 changed files with 26 additions and 0 deletions
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26
ecp5/pack.cc
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@ -359,6 +359,32 @@ class Ecp5Packer
flush_cells();
}
void set_lut_input_constant(CellInfo *cell, IdString input, bool value)
{
int index = std::string("ABCD").find(input.str(ctx));
int init = int_or_default(cell->params, ctx->id("INIT"));
int new_init = 0;
for (int i = 0; i < 16; i++) {
if (((i >> index) & 0x1) != value) {
int other_i = (i & (~(1 << index))) | (value << index);
if ((init >> other_i) & 0x1)
new_init |= (1 << i);
} else {
if ((init >> i) & 0x1)
new_init |= (1 << i);
}
}
cell->params[ctx->id("INIT")] = std::to_string(init);
NetInfo *innet = cell->ports.at(input).net;
if (innet != nullptr) {
innet->users.erase(
std::remove_if(innet->users.begin(), innet->users.end(),
[cell, input](PortRef port) { return port.cell == cell && port.port == input; }),
innet->users.end());
}
cell->ports.at(input).net = nullptr;
}
public:
void pack()
{