caiyu/nextpnr
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

mistral: Write arith mode to bitstream (not yet functional)

Browse Source 
Signed-off-by: gatecat <gatecat@ds0.me>
This commit is contained in:
gatecat 2021-05-12 20:41:52 +01:00
parent d39e67da7e
commit 2f2fde7e6c
2 changed files with 18 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
mistral/bitstream.cc
View File

@ -222,6 +222,9 @@ struct MistralBitgen
cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF0, alm, CycloneV::NLUT); cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF0, alm, CycloneV::NLUT);
cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF1, alm, CycloneV::NLUT); cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF1, alm, CycloneV::NLUT);
cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF1L, alm, CycloneV::NLUT); cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::BDFF1L, alm, CycloneV::NLUT);
if ((luts[0] && luts[0]->combInfo.is_carry) || (luts[1] && luts[1]->combInfo.is_carry))
cv->bmux_m_set(CycloneV::LAB, pos, CycloneV::ARITH_SEL, alm, CycloneV::ADDER);
} }
void write_labs() void write_labs()

17
mistral/lab.cc
View File

@ -366,21 +366,34 @@ bool Arch::is_alm_legal(uint32_t lab, uint8_t alm) const
return false; return false;
} }
// Never allow two disjoint carry chains to accidentally stack bool carry_mode = false;
for (int i = 0; i < 2; i++) { for (int i = 0; i < 2; i++) {
if (!luts[i]) if (!luts[i])
continue; continue;
if (!luts[i]->combInfo.is_carry)
continue;
carry_mode = true;
// Never allow two disjoint carry chains to accidentally stack
if (luts[i]->combInfo.carry_start && carry_used(this, alm_data.lut_bels[i], id_CI)) if (luts[i]->combInfo.carry_start && carry_used(this, alm_data.lut_bels[i], id_CI))
return false; return false;
if (luts[i]->combInfo.carry_end && carry_used(this, alm_data.lut_bels[i], id_CO)) if (luts[i]->combInfo.carry_end && carry_used(this, alm_data.lut_bels[i], id_CO))
return false; return false;
} }
for (int i = 0; i < 2; i++) {
if (!luts[i])
continue;
// No mixing of carry and non-carry
if (luts[i]->combInfo.is_carry != carry_mode)
return false;
}
// For each ALM half; check FF control set sharing and input routeability // For each ALM half; check FF control set sharing and input routeability
for (int i = 0; i < 2; i++) { for (int i = 0; i < 2; i++) {
// There are two ways to route from the fabric into FF data - either routing through a LUT or using the E/F // There are two ways to route from the fabric into FF data - either routing through a LUT or using the E/F
// signals and SLOAD=1 (*PKREF*) // signals and SLOAD=1 (*PKREF*)
bool route_thru_lut_avail = !luts[i] && (total_lut_inputs < 8) && (used_lut_bits < 64); bool route_thru_lut_avail = !luts[i] && !carry_mode && (total_lut_inputs < 8) && (used_lut_bits < 64);
// E/F is available if this LUT is using 3 or fewer inputs - this is conservative and sharing can probably // E/F is available if this LUT is using 3 or fewer inputs - this is conservative and sharing can probably
// improve this situation // improve this situation
bool ef_available = (!luts[i] || luts[i]->combInfo.used_lut_input_count <= 3); bool ef_available = (!luts[i] || luts[i]->combInfo.used_lut_input_count <= 3);