diff options
Diffstat (limited to 'ice40/arch.cc')
| -rw-r--r-- | ice40/arch.cc | 29 |
1 files changed, 26 insertions, 3 deletions
diff --git a/ice40/arch.cc b/ice40/arch.cc index b36c82d5..6746b302 100644 --- a/ice40/arch.cc +++ b/ice40/arch.cc @@ -923,9 +923,20 @@ std::vector<GraphicElement> Arch::getDecalGraphics(DecalId decal) const bool Arch::getCellDelay(const CellInfo *cell, IdString fromPort, IdString toPort, DelayQuad &delay) const { - if (cell->type == id_ICESTORM_LC && cell->lcInfo.dffEnable) { - if (toPort == id_O) - return false; + if (cell->type == id_ICESTORM_LC) { + if (toPort == id_O) { + if (cell->lcInfo.dffEnable) + return false; + // "false paths" + if (fromPort == id_I0 && ((cell->lcInfo.lutInputMask & 0x1U) == 0)) + return false; + if (fromPort == id_I1 && ((cell->lcInfo.lutInputMask & 0x2U) == 0)) + return false; + if (fromPort == id_I2 && ((cell->lcInfo.lutInputMask & 0x4U) == 0)) + return false; + if (fromPort == id_I3 && ((cell->lcInfo.lutInputMask & 0x8U) == 0)) + return false; + } } else if (cell->type == id_ICESTORM_RAM || cell->type == id_ICESTORM_SPRAM) { return false; } @@ -1231,6 +1242,18 @@ void Arch::assignCellInfo(CellInfo *cell) cell->lcInfo.inputCount++; if (cell->getPort(id_I3)) cell->lcInfo.inputCount++; + // Find don't care LUT inputs to mask for timing analysis + cell->lcInfo.lutInputMask = 0x0; + unsigned init = int_or_default(cell->params, id_LUT_INIT); + for (unsigned k = 0; k < 4; k++) { + for (unsigned i = 0; i < 16; i++) { + // If toggling the LUT input makes a difference it's not a don't care + if (((init >> i) & 0x1U) != ((init >> (i ^ (1U << k))) & 0x1U)) { + cell->lcInfo.lutInputMask |= (1U << k); + break; + } + } + } } else if (cell->type == id_SB_IO) { cell->ioInfo.lvds = str_or_default(cell->params, id_IO_STANDARD, "SB_LVCMOS") == "SB_LVDS_INPUT"; cell->ioInfo.global = bool_or_default(cell->attrs, id_GLOBAL); |