[LLVMdev] Target specific info available to Clang (and others) (original) (raw)

Renato Golin renato.golin at linaro.org
Thu Oct 23 06:50:56 PDT 2014

So,

In order to fix bug PR20787 (common parsing infrastructure for FPU options between LLVM and tools), I need to create a parser in LLVM that has all targets' information (types of fpus, cpus, archs, etc) but that can also be visible by external tools.

Until now, all that information has been hidden from view by creating them with TableGen and leave them only visible to the target files. That makes a lot of sense, but I need some of that exposed.

Including generated files from LLVM works ok, but Clang can't see them. If I enable Clang to see them (by adding the include dir on the path), there will be nothing to stop people from including more than they should.

The kind of information I want to expose are the enums that identify features, mainly VFP/NEON/Crypto etc. This is in ARMGenSubtargetInfo.inc under GET_SUBTARGETINFO_ENUM.

One way I could think of, but it's controversial, is to generate two files: ARMGenSubtargetInfo.inc and ARMGenSubtargetInfoPublic.inc, the former in the current directory, the latter in a shared include path for all tools. That way, not only LLVM, but also Clang, llc, lld etc would be able to use the same parsing mechanism and understand the generated data (enums, structures) in the exact same way.

Attached are two pseudo-patches that illustrate the problem. The Clang patch shows how much more powerful could such infrastructure become. The patch doesn't compile on Clang because Clang cannot see ARMGenSubtargetInfo.inc.

References:

http://llvm.org/bugs/show_bug.cgi?id=20787 http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-August/038699.html http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140811/231052.html

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