[llvm-commits] [llvm] r168829 - /llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp

[Bill Wendling]

There's no testcase that would work here. CGP is run way too late in the process, and dead blocks aren't passed into CodeGen. This is a pre-patch for future work, which should land soon.

-bw

On Nov 29, 2012, at 8:53 AM, Rafael Espíndola <rafael.espindola at gmail.com> wrote:

> testcase?
> 
> On 28 November 2012 18:23, Bill Wendling <isanbard at gmail.com> wrote:
>> Author: void
>> Date: Wed Nov 28 17:23:48 2012
>> New Revision: 168829
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=168829&view=rev
>> Log:
>> When we delete a dead basic block, see if any of its successors are dead and
>> delete those as well.
>> 
>> Modified:
>>    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
>> 
>> Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=168829&r1=168828&r2=168829&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Nov 28 17:23:48 2012
>> @@ -194,9 +194,19 @@
>>           WorkList.insert(*II);
>>     }
>> 
>> -    for (SmallPtrSet<BasicBlock*, 8>::iterator
>> -           I = WorkList.begin(), E = WorkList.end(); I != E; ++I)
>> -      DeleteDeadBlock(*I);
>> +    // Delete the dead blocks and any of their dead successors.
>> +    while (!WorkList.empty()) {
>> +      BasicBlock *BB = *WorkList.begin();
>> +      WorkList.erase(BB);
>> +      SmallVector<BasicBlock*, 2> Successors(succ_begin(BB), succ_end(BB));
>> +
>> +      DeleteDeadBlock(BB);
>> +
>> +      for (SmallVectorImpl<BasicBlock*>::iterator
>> +             II = Successors.begin(), IE = Successors.end(); II != IE; ++II)
>> +        if (pred_begin(*II) == pred_end(*II))
>> +          WorkList.insert(*II);
>> +    }
>> 
>>     // Merge pairs of basic blocks with unconditional branches, connected by
>>     // a single edge.
>> 
>> 
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