drt: pin access issues with EOL rules

[antonblanchard]

Describe the bug

I'm looking at an asap7 test where we get stuck quite a while because of EOL violations between M2 tracks connecting to two pins in a standard cell. Only M1 and M2 are visible here, and you can see the yellow box showing the DRC issue between the two pins. M2 has an EOLKEEPOUT rule:

 PROPERTY LEF58_EOLKEEPOUT "EOLKEEPOUT 0.025 EXTENSION 0.0 0.0125 0.031 CORNERONLY ; " ;

I notice a number of things:

• Pin access could do a better job of picking the initial APs:

There is quite a lot of space, but we've clustered them all together, almost guaranteeing an EOL violation. I know we turn off some of the rules during pin access, eg gcWorker.setIgnoreLongSideEOL();, and maybe this is contributing to it.

• gc seems to consider the complete keepout area:

  frCoord forward = constraint->getForwardExt();
  frCoord backward = constraint->getBackwardExt();
  frCoord side = constraint->getSideExt();

But rp (and so fixed cost/routing costs) only consider forward and side:

      eolSpace = std::max(eolSpace, con->getForwardExt());
      eolWithin = std::max(eolWithin, con->getSideExt());

Not an issue here, but might be nice to fix.

• Is there a better way to represent EOL CORNERONLY rules in fixed/routing costs? We place a planar cost, but since it's a CORNERONLY rule, then only a wire terminating on that grid point should be penalized (assuming I understand the rule correctly). A wire passing through should not have the cost applied:

Expected Behavior

We don't get stuck for multiple iterations creating the same DRC issue.

Environment

os: Fedora Linux 37 (Workstation Edition)
cmake version 3.26.2
-- The CXX compiler identification is GNU 12.2.1
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-- OpenROAD version: v2.0-7708-g4b1ea0d24
-- System name: Linux
-- Compiler: GNU 12.2.1
-- Build type: RELEASE
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--CMake Warning at src/CMakeLists.txt:226 (message):
  spdlog: SPDLOG_FMT_EXTERNAL=ON


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-- Found SWIG: /usr/bin/swig (found suitable version "4.0.2", minimum required is "3.0")  
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-- STA version: 2.4.0
-- STA git sha: 8de844d9d85b1eaa1bdf78d9b0e1dc8008e5183c
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-- TCL library: /usr/lib64/libtcl.so
-- TCL header: /usr/include/tcl.h
-- SSTA: 0
-- STA executable: /home/anton_unencrypted/OpenROAD/src/sta/app/sta
-- GPU is not enabled
-- Found Protobuf: /usr/lib64/libprotobuf.so (found version "3.19.6") 
-- Found re2: /usr/lib64/cmake/re2/re2Config.cmake (found version "9.0.0") 
-- Found Clp: /usr/local/lib64/cmake/Clp/ClpConfig.cmake (found version "1.17.7") 
-- Found Cbc: /usr/local/lib64/cmake/Cbc/CbcConfig.cmake (found version "2.10.7") 
-- Found Eigen3: /usr/share/cmake/eigen3/Eigen3Config.cmake (found version "3.4.0") 
-- Found SCIP: /usr/local/lib/cmake/scip/scip-config.cmake (found version "8.0.1") 
-- GUI is enabled
-- Found Boost: /usr/lib64/cmake/Boost-1.78.0/BoostConfig.cmake (found version "1.78.0") found components: serialization 
-- Found OpenMP_CXX: -fopenmp (found version "4.5") 
-- Found OpenMP: TRUE (found version "4.5")  
-- Could NOT find VTune (missing: VTune_LIBRARIES VTune_INCLUDE_DIRS) 
-- Found Boost: /usr/lib64/cmake/Boost-1.78.0/BoostConfig.cmake (found suitable version "1.78.0", minimum required is "1.78")  
-- Found Boost: /usr/lib64/cmake/Boost-1.78.0/BoostConfig.cmake (found version "1.78.0") found components: serialization system thread 
-- Found Boost: /usr/lib64/cmake/Boost-1.78.0/BoostConfig.cmake (found version "1.78.0")  
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To Reproduce

Test case is at https://ozlabs.org/~anton/junk/astar-eol-drc.tar.gz

Relevant log output

No response

Screenshots

No response

Additional Context

No response

[antonblanchard]

This is the eventual solution: