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-rw-r--r--techlibs/xilinx/synth_xilinx.cc12
1 files changed, 8 insertions, 4 deletions
diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc
index 41429b338..4fe287744 100644
--- a/techlibs/xilinx/synth_xilinx.cc
+++ b/techlibs/xilinx/synth_xilinx.cc
@@ -342,10 +342,14 @@ struct SynthXilinxPass : public ScriptPass
if (check_label("map_dsp", "(skip if '-nodsp')")) {
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_A_MINWIDTH=2 -D DSP_B_MINWIDTH=2 " // Blocks Nx1 multipliers
- "-D DSP_Y_MINWIDTH=9 " // UG901 suggests small multiplies are those 4x4 and smaller
- "-D DSP_SIGNEDONLY=1 -D DSP_NAME=$__MUL25X18");
+ run("techmap -map +/mul2dsp.v -map +/xilinx/dsp_map.v -D DSP_A_MAXWIDTH=25 "
+ "-D DSP_A_MAXWIDTH_PARTIAL=18 -D DSP_B_MAXWIDTH=18 " // Partial multipliers are intentionally
+ // limited to 18x18 in order to take
+ // advantage of the (PCOUT << 17) -> PCIN
+ // dedicated cascade chain capability
+ "-D DSP_A_MINWIDTH=2 -D DSP_B_MINWIDTH=2 " // Blocks Nx1 multipliers
+ "-D DSP_Y_MINWIDTH=9 " // UG901 suggests small multiplies are those 4x4 and smaller
+ "-D DSP_SIGNEDONLY=1 -D DSP_NAME=$__MUL25X18");
run("select a:mul2dsp");
run("setattr -unset mul2dsp");
run("opt_expr -fine");