[LLVMdev] Instruciton replacement

Chris Lattner sabre at nondot.org
Wed Nov 27 23:48:01 PST 2002

> llvm is giving me some assertion errors when trying to replace an
> instruction, and I'm not quite sure of what to do. I have the
> following snippet of code:
>     AI = new AllocaInst(cast<AllocationInst>(*I)->getAllocatedType(),
> 			cast<AllocationInst>(*I)->getArraySize());
>     (*I)->replaceAllUsesWith(AI);

> This is probably because you removed an LLVM value (Instruction,
> BasicBlock, etc), but didn't delete it.  Please check your code for
> memory leaks. Assertion failed: slot != -1 && "Broken bytecode!", file
> WriteInst.cpp, line 191 If I uncomment the (delete(AI)) will report:
> While deleting: uint *% Use still stuck around after Def is destroyed:
> %reg112 = load uint* <badref> ; <uint> [#uses=1] Use still stuck around
> after Def is destroyed:  store uint 37337, uint* <badref> Assertion
> failed: Uses.begin() == Uses.end(), file Value.cpp, line 43 Abort

Actually, the problem is that you are making things point to the new
alloca instruction you created, but you are not inserting the alloca
instruction into the program anywhere.  To do this, you can use the extra
argument to the AllocaInst ctor, specifying the instruction that the
alloca should be inserted before.



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