[LLVMdev] Remove identical or redundant basic blocks?

[Dale Johannesen]

The branch folding pass does this, but it operates later, on the  
target-dependent form in llc.

On May 8, 2010, at 8:48 AM, Heinz Riener wrote:

> Dear all,
>
> after optimizing a small LLVM example program (i.e., with opt -O3),  
> the
> resulting code contains several basic blocks, which I consider  
> identical
> or redundant.  For instance,
>
> return:                                           ; preds = %min.exit
>   ret i32 0
>
> bb15:                                             ; preds = %min.exit
>   ret i32 0
>
> or,
>
> bb7.i:                                            ; preds = %bb1.i
>   br label %bb3.i
>
> bb9.i:                                            ; preds = %bb1.i
>   br label %bb3.i
>
> I think it is safe to remove the blocks bb7.i, bb9.i, bb15 while
> replacing each jump to bb15 with return and jumps to bb7.i, bb9.i with
> bb3.i.
>
> Is there any opt pass I can apply to the code to merge or remove these
> blocks?
>
> Heinz
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