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Improve pmux2shift ctrl permutation finder 

Signed-off-by: Clifford Wolf <clifford@clifford.at>
This commit is contained in:
Clifford Wolf 2019-04-19 20:20:08 +02:00
parent 481f0015be
commit 177878cbb0
1 changed files with 114 additions and 27 deletions
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141
passes/opt/pmux2shiftx.cc
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@ -29,17 +29,29 @@ struct Pmux2ShiftxPass : public Pass {
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" pmux2shiftx [selection]\n");
log(" pmux2shiftx [options] [selection]\n");
log("\n");
log("This pass transforms $pmux cells to $shiftx cells.\n");
log("\n");
log(" -density non_offset_percentage offset_percentage\n");
log(" specifies the minimum density for non_offset- and for offset-mode\n");
log(" default values are 30 (non-offset) and 50 (offset)\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
{
int non_offset_percentage = 30;
int offset_percentage = 50;
log_header(design, "Executing PMUX2SHIFTX pass.\n");
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++) {
if (args[argidx] == "-density" && argidx+2 < args.size()) {
non_offset_percentage = atoi(args[++argidx].c_str());
offset_percentage = atoi(args[++argidx].c_str());
continue;
}
break;
}
extra_args(args, argidx, design);
@ -180,34 +192,108 @@ struct Pmux2ShiftxPass : public Pass {
// find the relevant choices
dict<Const, int> choices;
vector<int> onescnt(GetSize(sig));
for (int i : seldb.at(sig)) {
Const val = eqdb.at(S[i]).second;
choices[val] = i;
for (int k = 0; k < GetSize(val); k++)
if (val[k] == State::S1)
onescnt[k] |= 1;
else
onescnt[k] |= 2;
}
// TBD: also find choices that are using signals that are subsets of the bits in "sig"
// find the best permutation
vector<pair<int, int>> perm(GetSize(sig));
for (int i = 0; i < GetSize(onescnt); i++)
perm[i] = make_pair(onescnt[i], i);
// TBD: this is not the best permutation
std::sort(perm.rbegin(), perm.rend());
vector<int> perm_new_from_old(GetSize(sig));
Const perm_xormask(State::S0, GetSize(sig));
{
vector<int> values(GetSize(choices));
vector<bool> used_src_columns(GetSize(sig));
vector<vector<bool>> columns(GetSize(sig), vector<bool>(GetSize(values)));
for (int i = 0; i < GetSize(choices); i++) {
Const val = choices.element(i)->first;
for (int k = 0; k < GetSize(val); k++)
if (val[k] == State::S1)
columns[k][i] = true;
}
for (int dst_col = GetSize(sig)-1; dst_col >= 0; dst_col--)
{
int best_src_col = -1;
bool best_inv = false;
int best_maxval = 0;
int best_delta = 0;
// find best src colum for this dst column
for (int src_col = 0; src_col < GetSize(sig); src_col++)
{
if (used_src_columns[src_col])
continue;
int this_maxval = 0;
int this_minval = 1 << 30;
int this_inv_maxval = 0;
int this_inv_minval = 1 << 30;
for (int i = 0; i < GetSize(values); i++)
{
int val = values[i];
int inv_val = val;
if (columns[src_col][i])
val |= 1 << dst_col;
else
inv_val |= 1 << dst_col;
this_maxval = std::max(this_maxval, val);
this_minval = std::min(this_minval, val);
this_inv_maxval = std::max(this_inv_maxval, inv_val);
this_inv_minval = std::min(this_inv_minval, inv_val);
}
int this_delta = this_maxval - this_minval;
int this_inv_delta = this_maxval - this_minval;
bool this_inv = false;
if (this_delta != this_inv_delta)
this_inv = this_inv_delta < this_delta;
else if (this_maxval != this_inv_maxval)
this_inv = this_inv_maxval < this_maxval;
if (this_inv) {
this_delta = this_inv_delta;
this_maxval = this_inv_maxval;
this_minval = this_inv_minval;
}
bool this_is_better = false;
if (best_src_col < 0)
this_is_better = true;
else if (this_delta != best_delta)
this_is_better = this_delta < best_delta;
else if (this_maxval != best_maxval)
this_is_better = this_maxval < best_maxval;
else
this_is_better = sig[best_src_col] < sig[src_col];
if (this_is_better) {
best_src_col = src_col;
best_inv = this_inv;
best_maxval = this_maxval;
best_delta = this_delta;
}
}
used_src_columns[best_src_col] = true;
perm_new_from_old[dst_col] = best_src_col;
perm_xormask[dst_col] = best_inv ? State::S1 : State::S0;
}
}
// permutated sig
Const perm_xormask(State::S0, GetSize(sig));
SigSpec perm_sig(State::S0, GetSize(sig));
for (int i = 0; i < GetSize(sig); i++) {
if (perm[i].first == 1)
perm_xormask[i] = State::S1;
perm_sig[i] = sig[perm[i].second];
}
for (int i = 0; i < GetSize(sig); i++)
perm_sig[i] = sig[perm_new_from_old[i]];
log(" best permutation: %s\n", log_signal(perm_sig));
log(" best xor mask: %s\n", log_signal(perm_xormask));
@ -223,7 +309,7 @@ struct Pmux2ShiftxPass : public Pass {
Const new_c(State::S0, GetSize(old_c));
for (int i = 0; i < GetSize(old_c); i++)
new_c[i] = old_c[perm[i].second];
new_c[i] = old_c[perm_new_from_old[i]];
Const new_c_before_xor = new_c;
new_c = const_xor(new_c, perm_xormask, false, false, GetSize(new_c));
@ -236,18 +322,21 @@ struct Pmux2ShiftxPass : public Pass {
log(" %s -> %s -> %s\n", log_signal(old_c), log_signal(new_c_before_xor), log_signal(new_c));
}
int range_density = 100*GetSize(choices) / (max_choice-min_choice+1);
int absolute_density = 100*GetSize(choices) / (max_choice+1);
log(" choices: %d\n", GetSize(choices));
log(" min choice: %d\n", min_choice);
log(" max choice: %d\n", max_choice);
log(" range density: %d%%\n", 100*GetSize(choices)/(max_choice-min_choice+1));
log(" absolute density: %d%%\n", 100*GetSize(choices)/(max_choice+1));
log(" range density: %d%%\n", range_density);
log(" absolute density: %d%%\n", absolute_density);
bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (max_choice+1 == GetSize(choices));
log(" full case: %s\n", full_case ? "true" : "false");
// use arithmetic offset if density is less than 30%
// check density percentages
Const offset(State::S0, GetSize(sig));
if (3*GetSize(choices) < max_choice && 3*GetSize(choices) >= (max_choice-min_choice))
if (absolute_density < non_offset_percentage && range_density >= offset_percentage)
{
log(" using offset method.\n");
@ -259,10 +348,8 @@ struct Pmux2ShiftxPass : public Pass {
for (auto &it : perm_choices)
new_perm_choices[const_sub(it.first, offset, false, false, GetSize(sig))] = it.second;
perm_choices.swap(new_perm_choices);
}
// ignore cases with a absolute density of less than 30%
if (3*GetSize(choices) < max_choice) {
} else
if (absolute_density < non_offset_percentage) {
log(" insufficient density.\n");
seldb.erase(sig);
continue;