From f3a55d3f06a21af06a267b3f9da8bd4df3d4aa82 Mon Sep 17 00:00:00 2001 From: Eddie Hung Date: Tue, 10 Sep 2019 14:11:56 -0700 Subject: [PATCH] Add comment for why opt_expr is necessary --- techlibs/xilinx/synth_xilinx.cc | 2 ++ 1 file changed, 2 insertions(+) diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc index 2cf0bd4f9..c99b77905 100644 --- a/techlibs/xilinx/synth_xilinx.cc +++ b/techlibs/xilinx/synth_xilinx.cc @@ -325,6 +325,8 @@ struct SynthXilinxPass : public ScriptPass if (!nodsp || help_mode) { // NB: Xilinx multipliers are signed only run("techmap -map +/mul2dsp.v -map +/xilinx/dsp_map.v -D DSP_A_MAXWIDTH=25 -D DSP_A_MAXWIDTH_PARTIAL=18 -D DSP_B_MAXWIDTH=18 -D DSP_SIGNEDONLY=1 -D DSP_NAME=$__MUL25X18", "(skip if '-nodsp')"); + // Necessary for optimising away $shl cells, as well as $add cells + // that have inputs with 1'b0 LSBs run("opt_expr -fine", " (skip if '-nodsp')"); run("wreduce", " (skip if '-nodsp')"); run("xilinx_dsp", " (skip if '-nodsp')"); -- 2.30.2