diff options
Diffstat (limited to 'techlibs/xilinx/synth_xilinx.cc')
| -rw-r--r-- | techlibs/xilinx/synth_xilinx.cc | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc index 01e75b50e..5bfbd1583 100644 --- a/techlibs/xilinx/synth_xilinx.cc +++ b/techlibs/xilinx/synth_xilinx.cc @@ -284,8 +284,12 @@ struct SynthXilinxPass : public ScriptPass run("techmap -map +/cmp2lut.v -D LUT_WIDTH=6"); + // The actual behaviour of the Xilinx DSP is a signed 25x18 multiply + // Due to current limitations of mul2dsp, we are actually mapping as a 24x17 + // unsigned multiply with MSBs set to 1'b0 + if (!nodsp || help_mode) - run("techmap -map +/mul2dsp.v -D DSP_A_MAXWIDTH=25 -D DSP_B_MAXWIDTH=18 -D DSP_NAME=$__MUL25X18"); + run("techmap -map +/mul2dsp.v -D DSP_A_MAXWIDTH=24 -D DSP_B_MAXWIDTH=17 -D DSP_NAME=$__MUL25X18"); run("alumacc"); run("share"); |