<div style="font-family:arial,helvetica,sans-serif;font-size:10pt">On 5 December 2012 16:29, Bill Wendling <span dir="ltr"><<a href="mailto:isanbard@gmail.com" target="_blank">isanbard@gmail.com</a>></span> wrote:<br>

<div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On Dec 5, 2012, at 4:23 PM, Nick Lewycky <<a href="mailto:nlewycky@google.com">nlewycky@google.com</a>> wrote:<br>


<br>
> On 28 November 2012 15:23, Bill Wendling <<a href="mailto:isanbard@gmail.com">isanbard@gmail.com</a>> wrote:<br>
> Author: void<br>
> Date: Wed Nov 28 17:23:48 2012<br>
> New Revision: 168829<br>
><br>
> URL: <a href="http://llvm.org/viewvc/llvm-project?rev=168829&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=168829&view=rev</a><br>
> Log:<br>
> When we delete a dead basic block, see if any of its successors are dead and<br>
> delete those as well.<br>
><br>
> Modified:<br>
>     llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp<br>
><br>
> Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp<br>
> URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=168829&r1=168828&r2=168829&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=168829&r1=168828&r2=168829&view=diff</a><br>


> ==============================================================================<br>
> --- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)<br>
> +++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Nov 28 17:23:48 2012<br>
> @@ -194,9 +194,19 @@<br>
>            WorkList.insert(*II);<br>
>      }<br>
><br>
> -    for (SmallPtrSet<BasicBlock*, 8>::iterator<br>
> -           I = WorkList.begin(), E = WorkList.end(); I != E; ++I)<br>
> -      DeleteDeadBlock(*I);<br>
> +    // Delete the dead blocks and any of their dead successors.<br>
> +    while (!WorkList.empty()) {<br>
> +      BasicBlock *BB = *WorkList.begin();<br>
> +      WorkList.erase(BB);<br>
> +      SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));<br>
> +<br>
> +      DeleteDeadBlock(BB);<br>
><br>
> I think you need to set MadeChange = true here. I think this bug could actually manifest because we use MadeChange later on to decide whether we need to recalculate the domtree.<br>
><br>
</div></div>Okay.<br>
<div class="im"><br>
> +<br>
> +      for (SmallVectorImpl<BasicBlock*>::iterator<br>
> +             II = Successors.begin(), IE = Successors.end(); II != IE; ++II)<br>
> +        if (pred_begin(*II) == pred_end(*II))<br>
><br>
> What if the block includes a branch to itself?<br>
><br>
</div>Won't the predecessor list be non-empty then?<br></blockquote><div><br></div><div>Right, and the block is dead and we want to delete it, but won't. This isn't a bug, just a missed optz'n.</div><div>

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