maksfb
commented
5 years ago I don't have an experience with GHC, and I don't have an access to version 8.4.3. However, I tried 7.6.3 with the "Hello World" program, and although BOLT processes the binary, the resulting executable segfaults. It appears there are multiple custom control transfer tables that are embedded into the code, and they are unmarked in the symbol table. stg_ap_p_fast is once instance of a function that uses such tables. Again, I'm unfamiliar with GHC, and cannot know what is the purpose of this function.
In general, since GHC uses non-standard code sequences involving indirect jumps, it will require a special support in BOLT. How important is this for you? Do you have a large performance-critical application written in Haskell?
jberryman
I've just started experimenting with BOLT and was curious if it would work on a haskell binary. I'm building a hello world program with ghc 8.4.3, with
ghc --make hello.hs -o hello.Using this oneliner to do the perf/BOLT stuff, straight from README:
$ function bolt_stuff(){ perf record -e cycles:u -j any,u -o $1.data -- ./$1 ; perf2bolt -p $1.data -o perf.fdata $1 ; llvm-bolt $1 -o $1.bolt -data=perf.fdata -reorder-blocks=cache+ -reorder-functions=hfsort+ -split-functions=3 -split-all-cold -split-eh -dyno-stats }Getting this error from
llvm-boltI get basically identical errors when compiled with the LLVM backend (with
ghc --make -fllvm...).Let me know if I can help debug.