[LLVMdev] Debug information and JIT (original) (raw)

Paweł Bylica chfast at gmail.com
Fri Jul 27 08:41:56 PDT 2012

On Thu, Jul 26, 2012 at 5:25 PM, Duncan Sands <baldrick at free.fr> wrote:

Hi Paweł,

I have a problem that was reported some time ago but never received any solution. probably the reason that there is no action is surely that the old JIT implementation is being replaced with the new MCJIT implementation, so no-one feels very motivated to fix the old JIT since it is going away. Try passing -use-mcjit to lli. Ciao, Duncan.

Thanks for suggestion. Unfortunately, I can't check it now as MCJIT does not work with my project at the moment.

I have found a simple example in C that causes the crash:

int main() { goto L; L: int a = 0; return 0; }

What is compiled to:

define i32 @main() nounwind { entry: %retval = alloca i32, align 4 %a = alloca i32, align 4 store i32 0, i32* %retval br label %L, !dbg !12

L: ; preds = %entry call void @llvm.dbg.declare(metadata !{i32* %a}, metadata !14), !dbg !15 store i32 0, i32* %a, align 4, !dbg !16 ret i32 0, !dbg !17 }

The problem is with @llvm.dbg.declare which is the first instruction of the block. I reproduced the crash with lli on win32 and mingw32 but not on linux64.

See http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-November/036113.html http://llvm.org/bugs/showbug.cgi?id=6981

JIT emitter for X86 aborts when is asked to emit instruction for opcode 11 (DBGVALUE). That opcode comes from @llvm.dbg.declare intrinsic function. Should this intrinsic be removed in some earlier stage? -- Paweł Bylica

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