On 02/07/16 20:18, Walter F.J. Mueller wrote:
Hallo,
I've compared three ghdl setups
- ghdl 0.33 with llvm backend (from Pete Gavins .deb package)
- ghdl 0.33 with gcc backend (compiled from SourceForge source kit)
- ghdl 0.34dev with gcc backend (compiled from git master)
with two benchmark cases
- behavioral simulation (766 processes, many quite complex)
- post-synthesis functional simulation (6090 processes, mostly quite slim)
the code was generated by vivado with 'write_vhdl'
[...]
From this, certainly very slim base, I observe
1. gcc -O0 and llvm -O2 give similar compile and execution speed
2. gcc -O2 gives higher compile time, but also better execution speed
3. gcc -O2 clearly outperforms llvm -O2
Just a comment about that: in llvm, the tool (here ghdl) has to manually
register the optimization pass. This is currently not tuned in ghdl.
So, I suppose that 'just' adding more optimization pass and ordering
them properly for -O/-O2 in ghdl could improve the performance.
Tristan.
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