isSequential returns 0 for all cells in Nangate45

[mguthaus]

Describe the bug

If I call isSequential on a DFF_X1 master cell in Nangate45, it returns 0. It returns 1 on DFF cells in other technologies. Is it a problem with the lib parser?

Expected Behavior

Return 1 for DFF_X1 master cells.

Environment

[WARNING] Your current OpenROAD version is outdated.
It is recommened to pull the latest changes.
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kernel: Linux 6.0.12-76060012-generic
os: Pop!_OS 20.04 LTS
cmake version 3.29.6
-- The CXX compiler identification is GNU 9.4.0
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-- OpenROAD version: v2.0-18676-gc4ec647a4
-- System name: Linux
-- Compiler: GNU 9.4.0
-- Build type: RELEASE
-- Install prefix: /usr/local
-- C++ Standard: 17
-- C++ Standard Required: ON
-- C++ Extensions: OFF
-- The C compiler identification is GNU 9.4.0
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-- Looking for pthread_create in pthreads
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-- Found Threads: TRUE
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
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-- boost: 1.80.0
-- Found GTest: /home/mrg/class/cse122-222a-w25-playground/OpenROAD-flow-scripts/tools/install/OpenROAD/lib/cmake/GTest/GTestConfig.cmake (found version "1.14.0")
-- GTest: 1.14.0
-- Found Python3: /usr/include/python3.10 (found version "3.10.16") found components: Development Development.Module Development.Embed
-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.11")
-- spdlog: 1.15.0
-- Found BISON: /usr/bin/bison (found version "3.5.1")
-- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE)
-- STA version: 2.6.0
-- STA git sha: f71b38bbcecc8ddda3def4c24462522ff72f96ca
-- System name: Linux
-- Compiler: GNU 9.4.0
-- Build type: RELEASE
-- Build CXX_FLAGS: -O3 -DNDEBUG
-- Install prefix: /usr/local
-- Found FLEX: /usr/bin/flex (found version "2.6.4")
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- TCL readline library: /usr/lib/x86_64-linux-gnu/libtclreadline.so
-- TCL readline header: /usr/include/x86_64-linux-gnu/tclreadline.h
-- Check if compiler accepts -pthread
-- Check if compiler accepts -pthread - yes
-- CUDD library: /usr/local/lib/libcudd.a
-- CUDD header: /usr/local/include/cudd.h
-- SSTA: 0
-- Found SWIG: /usr/bin/swig4.0 (found suitable version "4.0.1", minimum required is "3.0")
-- STA executable: /home/mrg/class/cse122-222a-w25-playground/OpenROAD-flow-scripts/tools/OpenROAD/src/sta/app/sta
-- Found re2: /opt/or-tools/lib/cmake/re2/re2Config.cmake (found version "11.0.0")
-- Found Clp: /opt/or-tools/lib/cmake/Clp/ClpConfig.cmake (found version "1.17.7")
-- Found Cbc: /opt/or-tools/lib/cmake/Cbc/CbcConfig.cmake (found version "2.10.7")
-- Found SCIP: /opt/or-tools/lib/cmake/scip/scip-config.cmake (found version "9.0.0")
-- Found OpenMP_CXX: -fopenmp (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
-- Found OR-Tools: /opt/or-tools/lib/cmake/ortools (version: 9.11.4210)
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- Found OpenMP_C: -fopenmp (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
-- GUI is enabled
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0") found components: serialization
-- Could NOT find VTune (missing: VTune_LIBRARIES VTune_INCLUDE_DIRS)
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found suitable version "1.80.0", minimum required is "1.78")
-- TCL library: /usr/lib/x86_64-linux-gnu/libtcl.so
-- TCL header: /usr/include/tcl/tcl.h
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0") found components: serialization system thread
-- Found Boost: /usr/local/lib/cmake/Boost-1.80.0/BoostConfig.cmake (found version "1.80.0")
-- Found Eigen3: /usr/local/share/eigen3/cmake/Eigen3Config.cmake (found version "3.4.1")
-- TCL readline enabled
-- Tcl Extended disabled
-- Python3 enabled
-- Configuring done (9.2s)
-- Generating done (0.5s)
-- Build files have been written to: /tmp/tmp.enly1Gq9Bc

To Reproduce

Run make on the standard nangate45 gcd design. Then run this TCL script:

set TECH "nangate45"
set DESIGN "gcd"
set clk_pin "clk"

set VERILOG_FILE "results/$TECH/$DESIGN/base/6_final.v"
set ODB_FILE "results/$TECH/$DESIGN/base/6_final.odb"
set DEF_FILE "results/$TECH/$DESIGN/base/6_final.def"
set SDC_FILE "results/$TECH/$DESIGN/base/6_final.sdc"

set TECH_LEF "platforms/nangate45/lef/NangateOpenCellLibrary.tech.lef"
set SC_LEF "platforms/nangate45/lef/NangateOpenCellLibrary.macro.mod.lef"
set LIB_FILE "platforms/nangate45/lib/NangateOpenCellLibrary_typical.lib"

read_liberty $LIB_FILE

read_lef $TECH_LEF
read_lef $SC_LEF
read_def $DEF_FILE
read_sdc $SDC_FILE

set db [ord::get_db]
set block [ord::get_db_block]
set inst [$block findInst "ctrl.state.out\\\[0\\\]\$_DFF_P_"]
set inst_name [$inst getName]
set master [$inst getMaster]
set master_name [$master getName]
puts "$inst_name [$master getName] [$master isSequential]"

Relevant log output

OpenROAD v2.0-18676-gc4ec647a4
Features included (+) or not (-): +GPU +GUI +Python
This program is licensed under the BSD-3 license. See the LICENSE file for details.
Components of this program may be licensed under more restrictive licenses which must be honored.
[INFO ODB-0227] LEF file: platforms/nangate45/lef/NangateOpenCellLibrary.tech.lef, created 22 layers, 27 vias
[INFO ODB-0227] LEF file: platforms/nangate45/lef/NangateOpenCellLibrary.macro.mod.lef, created 135 library cells
[INFO ODB-0127] Reading DEF file: results/nangate45/gcd/base/6_final.def
[INFO ODB-0128] Design: gcd
[INFO ODB-0130]     Created 54 pins.
[INFO ODB-0131]     Created 859 components and 3523 component-terminals.
[INFO ODB-0132]     Created 2 special nets and 1718 connections.
[INFO ODB-0133]     Created 682 nets and 1802 connections.
[INFO ODB-0134] Finished DEF file: results/nangate45/gcd/base/6_final.def
ctrl.state.out\[0\]$_DFF_P_ DFF_X1 0

Screenshots

No response

Additional Context

No response

[maliberty]

I assume you are talking about dbMaster::isSequential. It is a leftover from the original contribution of OpenDB. It is not populated as it makes more sense to use sta for this. We could try to copy over the state but they you are left with questions like is an ICG a sequential? It has a statetable but its not what people usually think of. Sta has the full Liberty details.

[QuantamHD]

@maliberty Should we stub isSequential function with an implementation that pull from STA, and just remove the odb impl? Or just remove the function all together?

[QuantamHD]

Looks like it's used in a few places. Maybe some dead code around levelizing in dbBlock and also in dft.

[maliberty]

Looks like dbMTerm::create sets isSequential if you create a clock mterm. Its a pretty weak method but I suppose it would work on some pdks. The levelizing stuff is unused afaik.