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This is incorrect, the LLVM project has an official Fortran compiler in tree called flang: https://github.com/llvm/llvm-project/tree/master/flang https://github

This is incorrect, the LLVM project has an official Fortran compiler in tree called flang: https://github.com/llvm/llvm-project/tree/master/flang https://github.com/llvm/llvm-project/tree/master/flang It is quite hard to write portable Fortran code, but code that at least compiles with PGI should compile with that as well.

sitkack 6y ago
I wonder why this is allowed to persist? Have there been any studies across benchmark suites relative to compiler and platform? What was the spread? Was this general purpose, it works well enough speed or was this I need to get 1.75% better on task x or my super computer budget is blown? I find the whole Fortran ecosystem and lineage fascinating for some reason. Like an alternative universe where integers are only used for loop counters.
KenoFischer 6y ago
If you actually read the code, it turns out that said compiler is not yet capable of generating LLVM IR let alone binaries.
- fluffything 6y ago
  Wait what? We were using the old flang project just fine. I thought they just moved it in tree and keept developing it.
  - KenoFischer 6y ago
    There was old flang which was basically just the PGI compiler stripped of its backend and with a piece bolted on that converted the compiler's internal IR to LLVM by basically dumping out strings and then parsing them back in. Many people in the LLVM community thought that this was not a maintainable long term strategy for a Fortran frontend, and after much debate, the flang team decided to start over on Greenfield compiler called f18, which was to be architected more like clang. Then Chris released MLIR and said team decided to target that rather than LLVM directly. The only thing that was kept from old flang were some of the runtime libraries. f18 was recently merged into the llvm-project repository whereupon it was renamed flang. Old flang is dead, but the terminology is a bit confusing now. Additionally there are two external LLVM Fortran compiler efforts: lfortran out of the US national labs (which also paid PGI for flang) and fc, which I don't believe is currently open source, but is being developed by as compiler consulting shop on India called CompilerTree (not sure who's footing the bill for that one). Anyway, long story short, none of them seem to work. Old flang generates binaries, but is abandonware at this point, so not the correct foundation to build on. New flang doesn't even generate LLVM IR yet. FC doesn't seem public yet as I said. Lfortran may work, but the authors say it's very alpha and it certainly didn't work out of the box. I know some folks are looking into it to see what would be required.

sitkack 6y ago

I wonder why this is allowed to persist? Have there been any studies across benchmark suites relative to compiler and platform? What was the spread? Was this general purpose, it works well enough speed or was this I need to get 1.75% better on task x or my super computer budget is blown? I find the whole Fortran ecosystem and lineage fascinating for some reason. Like an alternative universe where integers are only used for loop counters.

KenoFischer 6y ago

If you actually read the code, it turns out that said compiler is not yet capable of generating LLVM IR let alone binaries.

fluffything 6y ago
Wait what? We were using the old flang project just fine. I thought they just moved it in tree and keept developing it.
- KenoFischer 6y ago
  There was old flang which was basically just the PGI compiler stripped of its backend and with a piece bolted on that converted the compiler's internal IR to LLVM by basically dumping out strings and then parsing them back in. Many people in the LLVM community thought that this was not a maintainable long term strategy for a Fortran frontend, and after much debate, the flang team decided to start over on Greenfield compiler called f18, which was to be architected more like clang. Then Chris released MLIR and said team decided to target that rather than LLVM directly. The only thing that was kept from old flang were some of the runtime libraries. f18 was recently merged into the llvm-project repository whereupon it was renamed flang. Old flang is dead, but the terminology is a bit confusing now. Additionally there are two external LLVM Fortran compiler efforts: lfortran out of the US national labs (which also paid PGI for flang) and fc, which I don't believe is currently open source, but is being developed by as compiler consulting shop on India called CompilerTree (not sure who's footing the bill for that one). Anyway, long story short, none of them seem to work. Old flang generates binaries, but is abandonware at this point, so not the correct foundation to build on. New flang doesn't even generate LLVM IR yet. FC doesn't seem public yet as I said. Lfortran may work, but the authors say it's very alpha and it certainly didn't work out of the box. I know some folks are looking into it to see what would be required.