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Himbaechel xilinx : DSP packing : Emit a non-fatal error message

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Adrien Prost-Boucle 2024-09-24 10:01:29 +02:00 committed by myrtle
parent 2031a067a0
commit 9da05b6001
2 changed files with 23 additions and 10 deletions
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2
himbaechel/uarch/xilinx/pack.h
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@ -210,7 +210,7 @@ struct XC7Packer : public XilinxPacker
void pack_dsps(); void pack_dsps();
private: private:
void walk_dsp(CellInfo *root, CellInfo *ci, int constr_z); unsigned walk_dsp(CellInfo *root, CellInfo *ci, int constr_z);
void check_valid_pad(CellInfo *ci, std::string type); void check_valid_pad(CellInfo *ci, std::string type);
}; };

31
himbaechel/uarch/xilinx/pack_dsp_xc7.cc
View File

@ -39,9 +39,11 @@ static bool is_cascade_output(const PortInfo& port, const Context *ctx)
return boost::starts_with(str, "ACOUT") || boost::starts_with(str, "BCOUT") || boost::starts_with(str, "PCOUT"); return boost::starts_with(str, "ACOUT") || boost::starts_with(str, "BCOUT") || boost::starts_with(str, "PCOUT");
} }
void XC7Packer::walk_dsp(CellInfo *root, CellInfo *current_cell, int constr_z) // Return : the number of DSP marked as cascaded
unsigned XC7Packer::walk_dsp(CellInfo *root, CellInfo *current_cell, int constr_z)
{ {
CellInfo *cascaded_cell = nullptr; CellInfo *cascaded_cell = nullptr;
unsigned num_casc = 0;
auto check_illegal_fanout = [&] (NetInfo *ni, std::string port) { auto check_illegal_fanout = [&] (NetInfo *ni, std::string port) {
if (ni->users.entries() > 1) if (ni->users.entries() > 1)
@ -75,21 +77,28 @@ void XC7Packer::walk_dsp(CellInfo *root, CellInfo *current_cell, int constr_z)
if (cascaded_cell != nullptr) { if (cascaded_cell != nullptr) {
auto is_lower_bel = constr_z == BEL_LOWER_DSP; auto is_lower_bel = constr_z == BEL_LOWER_DSP;
// Creating placement clusters is currently disabled, because the current constraints
// on Y coordinates don't always correspond to placement possibilities, which makes placer crash
// Explanation : the current offset +/-5 applies to DSP tiles, not to DSP slices
// But two cascaded DSPs can be placed in one tile, which does not correspond to a +/-5 offset
#if 0
cascaded_cell->cluster = root->name; cascaded_cell->cluster = root->name;
root->constr_children.push_back(cascaded_cell); root->constr_children.push_back(cascaded_cell);
cascaded_cell->constr_x = 0; cascaded_cell->constr_x = 0;
// the connected cell has to be above the current cell, // the connected cell has to be above the current cell,
// otherwise it cannot be routed, because the cascading ports // otherwise it cannot be routed, because the cascading ports
// are only connected to the DSP above // are only connected to the DSP above
// FIXME The offset +/-5 applies to DSP tiles, not to DSP slices
// So two cascaded DSPs can be placed in one tile, which does not correspond to a +/-5 offset
auto previous_y = (current_cell == root) ? 0 : current_cell->constr_y; auto previous_y = (current_cell == root) ? 0 : current_cell->constr_y;
cascaded_cell->constr_y = previous_y + (is_lower_bel ? -5 : 0); cascaded_cell->constr_y = previous_y + (is_lower_bel ? -5 : 0);
cascaded_cell->constr_z = constr_z; cascaded_cell->constr_z = constr_z;
cascaded_cell->constr_abs_z = true; cascaded_cell->constr_abs_z = true;
#endif
walk_dsp(root, cascaded_cell, is_lower_bel ? BEL_UPPER_DSP : BEL_LOWER_DSP); num_casc += 1;
num_casc += walk_dsp(root, cascaded_cell, is_lower_bel ? BEL_UPPER_DSP : BEL_LOWER_DSP);
} }
return num_casc;
} }
void XC7Packer::pack_dsps() void XC7Packer::pack_dsps()
@ -102,6 +111,7 @@ void XC7Packer::pack_dsps()
std::vector<CellInfo *> all_dsps; std::vector<CellInfo *> all_dsps;
// Clean connections of DSPs
for (auto &cell : ctx->cells) { for (auto &cell : ctx->cells) {
CellInfo *ci = cell.second.get(); CellInfo *ci = cell.second.get();
@ -155,6 +165,7 @@ void XC7Packer::pack_dsps()
} }
} }
// Find the roots of cascaded DSP
std::vector<CellInfo *> dsp_roots; std::vector<CellInfo *> dsp_roots;
for (auto ci : all_dsps) { for (auto ci : all_dsps) {
bool cascade_input_used = false; bool cascade_input_used = false;
@ -171,15 +182,17 @@ void XC7Packer::pack_dsps()
} }
} }
// Creating placement clusters is currently disabled, because the current constraints // Create clusters of cascaded DSPs
// on Y coordinates don't always correspond to placement possibilities, which makes placer crash unsigned num_casc = 0;
#if 0
for (auto root : dsp_roots) { for (auto root : dsp_roots) {
root->constr_abs_z = true; root->constr_abs_z = true;
root->constr_z = BEL_LOWER_DSP; root->constr_z = BEL_LOWER_DSP;
walk_dsp(root, root, BEL_UPPER_DSP); num_casc += walk_dsp(root, root, BEL_UPPER_DSP);
}
if(num_casc > 0) {
log_info("Found %u cascaded DSP from %u roots\n", num_casc, (unsigned)dsp_roots.size());
log_nonfatal_error("Cascaded DSP are currently not supported by the placer, the design will probably not be functional\n");
} }
#endif
} }
NEXTPNR_NAMESPACE_END NEXTPNR_NAMESPACE_END