diff options
| -rw-r--r-- | ice40/pack.cc | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/ice40/pack.cc b/ice40/pack.cc index 242f8ceb..536b1b16 100644 --- a/ice40/pack.cc +++ b/ice40/pack.cc @@ -1181,20 +1181,26 @@ static void pack_special(Context *ctx) log_info(" PLL '%s' has LOCK output, need to pass all outputs via LUT\n", ci->name.c_str(ctx)); bool found_lut = false; bool all_luts = true; + bool found_carry = false; unsigned int lut_count = 0; for (const auto &user : port.net->users) { NPNR_ASSERT(user.cell != nullptr); if (user.cell->type == ctx->id("ICESTORM_LC")) { - found_lut = true; - lut_count++; + if (bool_or_default(user.cell->params, ctx->id("CARRY_ENABLE"), false)) { + found_carry = true; + all_luts = false; + } else { + found_lut = true; + lut_count++; + } } else { all_luts = false; } } - if (found_lut && all_luts) { + if (found_lut && all_luts && lut_count < 8) { // Every user is a LUT, carry on now. - } else if (found_lut && !all_luts && lut_count < 8) { + } else if (found_lut && !all_luts && !found_carry && lut_count < 8) { // Strategy: create a pass-through LUT, move all non-LUT users behind it. log_info(" LUT strategy for %s: move non-LUT users to new LUT\n", port.name.c_str(ctx)); auto pt = spliceLUT(ctx, packed.get(), port.name, true); |