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Add comments for xilinx_dsp

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This commit is contained in:
Eddie Hung 2019-10-04 12:40:34 -07:00
parent b47bb5c810
commit cf82b38478
3 changed files with 134 additions and 6 deletions
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14
passes/pmgen/xilinx_dsp.cc
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@ -608,8 +608,13 @@ struct XilinxDspPass : public Pass {
extra_args(args, argidx, design);
for (auto module : design->selected_modules()) {
// Experimental feature: pack $add/$sub cells with
// (* use_dsp48="simd" *) into DSP48E1's using its
// SIMD feature
xilinx_simd_pack(module, module->selected_cells());
// Match for all features ([ABDMP][12]?REG, pre-adder,
// (post-adder, pattern detector, etc.) except for CREG
{
xilinx_dsp_pm pm(module, module->selected_cells());
pm.run_xilinx_dsp_pack(xilinx_dsp_pack);
@ -618,14 +623,17 @@ struct XilinxDspPass : public Pass {
// is no guarantee that the cell ordering corresponds
// to the "expected" case (i.e. the order in which
// they appear in the source) thus the possiblity
// existed that a register got packed as CREG into a
// existed that a register got packed as a CREG into a
// downstream DSP that should have otherwise been a
// PREG of an upstream DSP that had not been pattern
// matched yet
// PREG of an upstream DSP that had not been visited
// yet
{
xilinx_dsp_CREG_pm pm(module, module->selected_cells());
pm.run_xilinx_dsp_packC(xilinx_dsp_packC);
}
// Lastly, identify and utilise PCOUT -> PCIN,
// ACOUT -> ACIN, and BCOUT-> BCIN dedicated cascade
// chains
{
xilinx_dsp_cascade_pm pm(module, module->selected_cells());
pm.run_xilinx_dsp_cascade();