[LLVMdev] big bitcode files producing bad ARM asm

Alexander MacDonald alexmac at adobe.com
Mon Apr 25 20:17:33 PDT 2011

On 25 Apr 2011, at 18:20, Jakob Stoklund Olesen wrote:
> On Apr 25, 2011, at 6:01 PM, Alexander MacDonald wrote:
>> I have a rather large bitcode file which when run through "llc -march arm -O0" produces an asm file of about 500Mb. Trying to assemble this file with the ios assembler on osx gives me lots of "branch out of range" errors thanks to jump instructions overflowing the +/-32Mb relative jump limit.
>> I've tried running llc with the hidden "-arm-long-calls" option, which solves the problem but forces everything to be an indirect branch. That feels a bit like overkill, does anybody have a suggestion for what the right solution might be?
> I don't think any other solutions are currently supported.
> One problem is that the linker can move functions around as it pleases, so there is no way of knowing which functions are going to be far away.

But the linker will fix branches that become "long-calls" after it's shuffled things around right? so it would still be reasonable to try to get LLVM to at least codegen a single object file correctly, assuming that the codegen phase has some knowledge of roughly how big the branches will have to be when it is generating the asm, which on second thought it probably doesn't unless it knows the size of all functions before writing out the asm (I'm not too familiar with the codegen phase).

More information about the llvm-dev mailing list