[LLVMdev] instructions copy

[John Criswell]

Dear Yuxi,

I haven't used the clone() method of the Instruction class, but if I had 
to guess, the problem is that you're not changing the operands of the 
new instructions to reference the new instructions.  When you clone an 
instruction, the operands of the new instruction are identical to the 
operands of the old instruction.

In your example, if you clone the store, the store is still referencing 
%1 from the original LoadInst in the original basic block.  You need to 
change the new store's operand to be the new LoadInst that you created 
in your new BasicBlock.

You may also want to look at the llvm::CloneBasicBlock() function.  This 
utility function clones basic blocks; you can take a look at what it 
does and see how it works.

Regards,

John Criswell

On 7/11/15 6:13 PM, Yuxi Chen wrote:
> Hi,
>
> I want to copy some dependent statements, like a = b, b = c, from one 
> basicblock to another basicblocks.
> Because of SSA, a = b, will be like %1 = load %b, store %1, %a.
> If I just use clone() method in Instruction class, it will be like 
> <badref> = load %b, store <badref>, %a.
> If I need remap the virtual registers, this map just will affect the 
> whole module? And how to use it? I am a bit confused.
>
> Any suggestion will be appreciated.
>
> Best,
> Yuxi
> Uchicago
>
>
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-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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