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YosysHQ / oss-cad-suite-build

Multi-platform nightly builds of open source digital design and verification tools
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Both GHDL and Yosys from oss-cad-suite execute much slower than from deprecated fpga-toolchain #18

Closed cpldcpu closed 2 years ago

cpldcpu commented 2 years ago

Previously I used GHDL and Yosys from the fpga-toolchain build and tried to switch to the oss-cad suite now. For some reason both GHDL and Yosys became much slower. Please see below for examples.

The designs I am typically working with are rather small. I am using WSL2 (ubuntu) on the same Windows 10 machine.

The fpga toolchain is activated via default path, while I use the 'environment' script to activate the oss-cad-build

The slow down does not really depend on the actual optimization steps I am performing. I also set up the oss-cad chain on another machine and it also seemed slower than expected.

GHDL

Nov-15 build from oss cad suite (GHDL 2.0.0-dev (1.0.0.r870.ge3c865e8.dirty) [Dunoon edition]) grafik fpga toolchain (GHDL 2.0.0-dev (tarball) [Dunoon edition] open-tool-forge.nightly-20210717) grafik

Yosys

Nov-15 build from oss cad suite grafik fpga toolchain grafik

Edit: The synthesis script actually also calls GHDL. When I remove the GHDL invocation, the execution time difference reduces to about 0.3s

Design is on this repo: https://github.com/cpldcpu/PCBFlow

cpldcpu commented 2 years ago

Ok, I found the solution: The Version in the OSS CAD suite is complied with LLVM, the other one I had uses mcode.

Closing.