llvm --enable-tbaa forces LLVM to be 2.9 or above

[pmonday]

I compiled the latest master against LLVM 2.8. The compile worked initially, but when using the ghc-stage2 compiler against new code with the fllvm option, all programs fail to compile with: opt: Unknown command line argument '--enable-tbaa=true'. Try: 'opt -help'

This is the result of the following flags being added to: ghc/compiler/main/DriverPipeline.hs

tbaa | dopt Opt_LlvmTBAA dflags = "--enable-tbaa=true"

| otherwise = "--enable-tbaa=false"

--enable-tbaa is available on opt version 2.9 and above only.

It would be helpful if the ./configure script verified that the opt (and possibly llc) versions were 2.9 or above.

[dterei]

Yes this is a known issue. I'm experimenting with some features in the backend that require 2.9 but will get around to making this a runtime detected feature sometime soon.

[dterei]

Fixed in 878371810de61632d58962608fb3db588d9c2fbd.