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syn: Add combinational mapper unit tests
Assisted-by: Claude (various models) Signed-off-by: Martin Povišer <povik@cutebit.org>
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5 files changed

Lines changed: 393 additions & 1 deletion

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‎src/syn/include/syn/synthesis.h‎

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@@ -117,10 +117,15 @@ class Synthesis : public sta::dbStaState
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// Free-function entry points re-declared here so tests don't need to
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// pull in the private flow/ headers. The Synthesis methods of the same
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// names forward to these.
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void bitblast(Graph& g, bool blast_arith = true);
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void mapSequentials(Graph& g,
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sta::Network* network,
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utl::Logger* logger,
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const Synthesis& syn);
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void mapCombinationals(Graph& g,
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sta::Network* network,
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utl::Logger* logger,
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const Synthesis& syn);
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void abcRoundtrip(Graph& g, const std::string& commands, utl::Logger* logger);
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void livenessOpt(Graph& g,
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utl::Logger* logger,

‎src/syn/test/BUILD‎

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@@ -76,6 +76,22 @@ cc_test(
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],
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)
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cc_test(
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name = "cm_test",
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srcs = [
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"cm_test.cc",
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"equivalence_check.h",
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],
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data = ["cm_test_cells.lib"],
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features = ["-layering_check"],
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deps = [
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"//src/syn",
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"//src/syn/src/ir",
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"//src/tst",
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"@googletest//:gtest",
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],
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)
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cc_test(
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name = "abc_test",
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srcs = ["abc_test.cc"],

‎src/syn/test/CMakeLists.txt‎

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@@ -32,7 +32,7 @@ target_link_libraries(liveness_test GTest::gtest syn_flow syn_ir utl_lib)
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gtest_discover_tests(liveness_test WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
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add_dependencies(build_and_test liveness_test)
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foreach(_t abc_test sm_test)
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foreach(_t abc_test sm_test cm_test)
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add_executable(${_t} ${_t}.cc)
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target_link_libraries(${_t} ${_syn_test_libs} syn_lib syn_flow syn_ir tst)
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gtest_discover_tests(${_t} WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})

‎src/syn/test/cm_test.cc‎

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@@ -0,0 +1,246 @@
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// SPDX-License-Identifier: BSD-3-Clause
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// Copyright (c) 2026, The OpenROAD Authors
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#include <memory>
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#include <sstream>
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#include <string>
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#include <string_view>
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#include "equivalence_check.h"
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#include "gtest/gtest.h"
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#include "syn/ir/Graph.h"
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#include "syn/ir/Instance.h"
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#include "syn/synthesis.h"
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#include "tst/fixture.h"
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// ABC ships its own main() that wins over gtest_main when linked in.
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// Provide our own to force the gtest entry point.
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int main(int argc, char** argv)
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{
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testing::InitGoogleTest(&argc, argv);
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return RUN_ALL_TESTS();
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}
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namespace syn {
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struct CmTestCase
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{
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std::string_view name;
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std::string_view ir;
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// Best observed post-mapping area + 20% headroom.
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float area_threshold;
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};
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// Net IDs 0/1/2 are the constant tie-off slots; instance IDs start at %3.
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static const CmTestCase kCmTestCases[] = {
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{.name = "SingleAnd",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = and %3 %4
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%6:0 = output "y" %5
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)",
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.area_threshold = 3.6f},
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{.name = "NandFromAndThenNot",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = and %3 %4
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%6:1 = not %5
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%7:0 = output "y" %6
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)",
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.area_threshold = 2.4f},
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{.name = "NorFromOrThenNot",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = or %3 %4
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%6:1 = not %5
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%7:0 = output "y" %6
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)",
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.area_threshold = 2.4f},
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{.name = "Andnot",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = andnot %3 %4
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%6:0 = output "y" %5
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)",
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.area_threshold = 3.6f},
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{.name = "AoiPattern",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = input "c"
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%6:1 = or %4 %5
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%7:1 = and %3 %6
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%8:1 = not %7
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%9:0 = output "y" %8
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)",
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.area_threshold = 4.8f},
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{.name = "OrOfAnds",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = input "c"
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%6:1 = input "d"
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%7:1 = and %3 %4
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%8:1 = and %5 %6
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%9:1 = or %7 %8
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%10:0 = output "y" %9
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)",
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.area_threshold = 7.2f},
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{.name = "SharedFanin",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = input "c"
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%6:1 = and %3 %4
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%7:1 = and %3 %5
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%8:0 = output "y1" %6
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%9:0 = output "y2" %7
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)",
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.area_threshold = 7.2f},
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{.name = "FourInputAndTree",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = input "c"
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%6:1 = input "d"
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%7:1 = and %3 %4
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%8:1 = and %5 %6
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%9:1 = and %7 %8
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%10:0 = output "y" %9
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)",
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.area_threshold = 7.2f},
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// y = (a & !s) | (b & s)
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{.name = "MuxFromAig",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = input "b"
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%5:1 = input "s"
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%6:1 = andnot %3 %5
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%7:1 = and %4 %5
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%8:1 = or %6 %7
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%9:0 = output "y" %8
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)",
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.area_threshold = 8.4f},
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{.name = "ConstantOutput",
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.ir = R"(
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%3:0 = output "y0" 0
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%4:0 = output "y1" 1
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)",
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.area_threshold = 2.4f},
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{.name = "InverterOnly",
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.ir = R"(
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%3:1 = input "a"
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%4:1 = not %3
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%5:0 = output "y" %4
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)",
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.area_threshold = 1.2f},
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// 12-bit adder: bitblast lowers `adc` to Han-Carlson AIG. Output is
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// the 12-bit sum, dropping the carry-out at bit 12.
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{.name = "Adder12",
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.ir = R"(
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%3:12 = input "a"
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%15:12 = input "b"
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%27:13 = adc %3:12 %15:12 0
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%40:0 = output "y" %27+0:12
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)",
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.area_threshold = 280.8f},
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// Truncated 6x6 unsigned multiplier (syn::Mul outputWidth = a.width()).
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// bitblast lowers it to a Wallace tree feeding a Han-Carlson adder.
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{.name = "Multiplier6",
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.ir = R"(
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%3:6 = input "a"
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%9:6 = input "b"
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%15:6 = mul %3:6 %9:6
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%21:0 = output "y" %15:6
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)",
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.area_threshold = 265.2f},
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};
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class CmTest : public tst::Fixture,
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public ::testing::WithParamInterface<CmTestCase>
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{
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protected:
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void SetUp() override
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{
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Fixture::SetUp();
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readLiberty(getFilePath("_main/src/syn/test/cm_test_cells.lib"));
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synthesis_ = std::make_unique<Synthesis>(getDb(),
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getSta(),
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/*resizer=*/nullptr,
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getLogger());
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}
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std::unique_ptr<Synthesis> synthesis_;
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};
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TEST_P(CmTest, MapsBelowAreaAndIsEquivalent)
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{
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const CmTestCase& tc = GetParam();
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// bitblast lowers xor/adc/mul/… to AIG; mapper only handles And/Andnot/Or.
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std::istringstream gold_is{std::string(tc.ir)};
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std::unique_ptr<Graph> gold = Graph::parse(gold_is);
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bitblast(*gold);
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gold->normalize();
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std::istringstream gate_is{std::string(tc.ir)};
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std::unique_ptr<Graph> gate = Graph::parse(gate_is);
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bitblast(*gate);
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mapCombinationals(*gate, getSta()->network(), getLogger(), *synthesis_);
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// Surviving instances must be Targets, plus IR scaffolding and the
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// naming-only Nots that cm.cc:integrate() leaves behind.
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float area = 0.0f;
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gate->forEachInstance([&](const Instance* inst) {
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if (inst->is<Input>() || inst->is<Output>() || inst->is<Name>()
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|| inst->is<Not>() || inst->is<TieLow>() || inst->is<TieHigh>()
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|| inst->is<TieX>()) {
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return;
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}
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if (!inst->is<Target>()) {
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std::ostringstream os;
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gate->dumpInstance(os, inst);
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ADD_FAILURE() << "Non-Target instance survived combinational mapping in "
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"case "
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<< tc.name << ": " << os.str();
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return;
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}
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if (auto* t = inst->try_as<Target>()) {
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area += t->cell()->area();
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}
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});
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EXPECT_LE(area, tc.area_threshold)
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<< "Mapped area " << area << " exceeds threshold " << tc.area_threshold
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<< " (best observed + 20% headroom) for case " << tc.name;
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EXPECT_TRUE(equivalenceCheck(
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*gold, *gate, /*inputsDefined=*/true, /*allowRefinement=*/false))
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<< "Combinational mapping changed the function for case " << tc.name;
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}
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INSTANTIATE_TEST_SUITE_P(Cm,
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CmTest,
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::testing::ValuesIn(kCmTestCases),
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[](const ::testing::TestParamInfo<CmTestCase>& info) {
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return std::string(info.param.name);
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});
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} // namespace syn

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