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2f0f10cb87
The input to a shift operation is padded. This reduced the final number of MUX cells but during techmap it can create huge temporary multiplexers in the log shifter. This significantly increases runtime and resources. A limit is added with a warning when it is used.
99 lines
3.4 KiB
C++
99 lines
3.4 KiB
C++
/*
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* yosys -- Yosys Open SYnthesis Suite
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*
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* Copyright (C) 2012 Claire Xenia Wolf <claire@yosyshq.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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*/
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#include "kernel/yosys.h"
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#include "kernel/sigtools.h"
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USING_YOSYS_NAMESPACE
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PRIVATE_NAMESPACE_BEGIN
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bool did_something;
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// scratchpad configurations for pmgen
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int shiftadd_max_ratio;
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#include "passes/pmgen/peepopt_pm.h"
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struct PeepoptPass : public Pass {
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PeepoptPass() : Pass("peepopt", "collection of peephole optimizers") { }
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void help() override
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{
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// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
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log("\n");
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log(" peepopt [options] [selection]\n");
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log("\n");
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log("This pass applies a collection of peephole optimizers to the current design.\n");
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log("\n");
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log("This pass employs the following rules:\n");
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log("\n");
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log(" * muldiv - Replace (A*B)/B with A\n");
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log("\n");
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log(" * shiftmul - Replace A>>(B*C) with A'>>(B<<K) where C and K are constants\n");
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log(" and A' is derived from A by appropriately inserting padding\n");
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log(" into the signal. (right variant)\n");
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log("\n");
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log(" Analogously, replace A<<(B*C) with appropriate selection of\n");
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log(" output bits from A<<(B<<K). (left variant)\n");
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log("\n");
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log(" * shiftadd - Replace A>>(B+D) with (A'>>D)>>(B) where D is constant and\n");
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log(" A' is derived from A by padding or cutting inaccessible bits.\n");
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log(" Scratchpad: 'peepopt.shiftadd.max_data_multiple' (default: 2)\n");
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log(" limits the amount of padding to a multiple of the data, \n");
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log(" to avoid high resource usage from large temporary MUX trees.\n");
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log("\n");
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}
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void execute(std::vector<std::string> args, RTLIL::Design *design) override
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{
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log_header(design, "Executing PEEPOPT pass (run peephole optimizers).\n");
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size_t argidx;
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for (argidx = 1; argidx < args.size(); argidx++)
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{
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break;
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}
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extra_args(args, argidx, design);
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// limit the padding from shiftadd to a multiple of the input data
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// during techmap it creates (#data + #padding) * log(shift) $_MUX_ cells
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// 2x implies there is a constant shift larger than the input-data which should be extremely rare
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shiftadd_max_ratio = design->scratchpad_get_int("peepopt.shiftadd.max_data_multiple", 2);
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for (auto module : design->selected_modules())
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{
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did_something = true;
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while (did_something)
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{
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did_something = false;
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peepopt_pm pm(module);
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pm.setup(module->selected_cells());
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pm.run_shiftadd();
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pm.run_shiftmul_right();
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pm.run_shiftmul_left();
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pm.run_muldiv();
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}
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}
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}
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} PeepoptPass;
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PRIVATE_NAMESPACE_END
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