llvm dev - Dec 2013 - [LLVMdev] [PATCH] Don't optimize out GDB JIT registrar

Hi,

We switched from compiling LLVM with gcc to clang (3.3) and it appears that
clang (correctly I think) optimizes away the GDBRegistrar's
__jit_debug_register_code() function that's used to trigger reading debug
info from JIT-ted code, breaking GDB support.

This patch forces it to leave the call using the method described here in
the 'noinline' section:

http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html

Cheers,
Andrew
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On Fri, Dec 20, 2013 at 11:18:46AM +0100, Andrew MacPherson
wrote:
> This patch forces it to leave the call using the method described here in
> the 'noinline' section:
Use asm volatile("":::"memory") to make sure that it
doesn't leave
trackes. The noinline can likely go in that case...

Joerg

Thanks Joerg.

I've made the change you suggested and verified that it still works. I
think the noinline is still required though as this function can be called
from a couple of places and gdb will want to set its breakpoint on the
single function address. Let me know if you think otherwise though.

Cheers,
Andrew


On Fri, Dec 20, 2013 at 11:52 AM, Joerg Sonnenberger <
joerg at britannica.bec.de> wrote:
> On Fri, Dec 20, 2013 at 11:18:46AM +0100, Andrew MacPherson wrote:
> > This patch forces it to leave the call using the method described here
in
> > the 'noinline' section:
>
> Use asm volatile("":::"memory") to make sure that it
doesn't leave
> trackes. The noinline can likely go in that case...
>
> Joerg
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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