llvm - llc: unsupported relocation on symbol -


problem

llc giving me following error:

llvm error: unsupported relocation on symbol

detailed compilation flow

i implementing llvm frontend middle-level ir (mir) of compiler, , after convert various methods many bitcode files, link them (llvm-link), optimize them (opt), convert them machine code (llc), make them shared library (clang it's linker wrapper), , dynamically load them. llc step fails of methods compiling!

step 1: llvm-link: merge many bitcode files

i may have many functions calling each other, llvm-link different bitcode files might interact each other. step has no issues. example:

llvm-link function1.bc function2.bc -o lnk.bc

step 2: opt: run optimization passes

for using following:

opt -o3 lnk.bc -o opt.bc

this step proceeds no issues, that's 1 causes problem! also, it's necessary because in future need step pass passes, e.g. loop-unroll

step 3: llc: generate machine code (pic)

i using following command:

llc -march=thumb -arm-reserve-r9 -mcpu=cortex-a9 -filetype=obj -relocation-model pic opt.bc -o obj.o

i have kept arch specific flags i've set in case contribute issue. using position independent code because on next step building shared object. command fails error i've written on top of answer.

step 4: clang: generate shared object

for cases step 3 fails, step isn't reached. if llc succeeds, step succeed too!

additional information

configuration

the following run on llvm3.6, runs on arm device.

things i've noticed

  • if omit -o3 (or other level) opt step, llc work.
  • if don't, , instead omit them llc, llc still fail. makes me think opt -o<level> causing issue.
  • if use llc directly work, won't able run specific passes opt allows me, not option me.
  • i've faced issue only 2 functions i've compiled far (from original mir), use loops. others produce working code!
  • if don't use pic model @ llc, can generate obj.o, i'll have problems creating .so it!

questions

  1. why happening??!!

  2. why opt has -relocation-model option? isn't supposed llc thing? i've tried setting both @ opt , llc pic, still fails.

  3. i using clang because has wrapper linker the .so. there way step llvm tool instead?

first of all, not use neither llc nor opt. these developer-side tools should never used in production environment. instead of this, implement own proper optimization , codegeneration runtime via llvm libraries.

as particular bug - thumb codegenerator might contain bugs. please reduce problem , report it. or don't use thumb mode @ :)


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