llvm dev - Aug 2010 - [LLVMdev] JITing code with indirect branch in LLVM 2.7

I am trying to JIT some code containing an indirect branch (and the
corresponding  store i8* blockaddress(@label)). I am using LLVM 2.7
code base. I build the ExecutionEngine using EngineBuilder, and call
engine->getPointerToFunction(func). When I use
setOptLevel(llvm::CodeGenOpt::None), the JITing fails with the
following message :

JIT.h:131: virtual void*
llvm::JIT::getPointerToBasicBlock(llvm::BasicBlock*): Assertion `0 &&
"JIT does not support address-of-label yet!"' failed.

However, when I use setOptLevel(llvm::CodeGenOpt::Less) or higher
(Default, Aggressive), the assertion does not happen. However, when I
disassemble the JITed program, I see that the label getting stored is
wrong, it is not in the range of the function's code space. I am
wondering whether I am doing something wrong. Does the JIT mode not
support indirect branches?

Manjunath

Here's the bug about it:
http://llvm.org/bugs/show_bug.cgi?id=6744

There's a patch in progress there.

Reid

On Wed, Aug 4, 2010 at 2:40 PM, Manjunath Kudlur <keveman at gmail.com>
wrote:
> I am trying to JIT some code containing an indirect branch (and the
> corresponding  store i8* blockaddress(@label)). I am using LLVM 2.7
> code base. I build the ExecutionEngine using EngineBuilder, and call
> engine->getPointerToFunction(func). When I use
> setOptLevel(llvm::CodeGenOpt::None), the JITing fails with the
> following message :
>
> JIT.h:131: virtual void*
> llvm::JIT::getPointerToBasicBlock(llvm::BasicBlock*): Assertion `0
&&
> "JIT does not support address-of-label yet!"' failed.
>
> However, when I use setOptLevel(llvm::CodeGenOpt::Less) or higher
> (Default, Aggressive), the assertion does not happen. However, when I
> disassemble the JITed program, I see that the label getting stored is
> wrong, it is not in the range of the function's code space. I am
> wondering whether I am doing something wrong. Does the JIT mode not
> support indirect branches?
>
> Manjunath
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