[LLVMdev] "-march" trashing ARM triple

[David Meyer]

ARM subtarget features are determined by parsing the target tuple string
TT. (ParseARMTriple(StringRef TT) in ARMMCTargetDesc.cpp)

In llc, the -march setting overrides the architecture specified in
-mtriple. So when you invoke:

$ llc -march arm -mtriple armv7-none-linux ...

ParseARMTriple() will see TT == "arm-none-linux" instead of
"armv7-none-linux". As a result, the target features will be set
generically. (Note that using "-march armv7" is not valid.)

This is clearly wrong, but I'm not clear on where/how this should be fixed.
Does the -march substitution need to happen at all? Could it be disabled
only for ARM? Should TargetTriple or -march be made more precise?

Thanks,
- pdox
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