[llvm] r351520 - Re-enable terminator folding in LoopSimplifyCFG: underlying bugs fixed

[Jordan Rupprecht via llvm-commits]

Here's the creduce + stack trace w/ a debug build:

$ cat /tmp/repro.c
int a, b, *c, d, e;
void f() {
  int g;
  for (;;) {
    for (; e; e = b) {
      c = g;
      for (; c; c = d)
        if (a) break;
      if (c) break;
    }
  }
}

$ clang -O1 -fexperimental-new-pass-manager -mllvm
-enable-loop-simplifycfg-term-folding -c /tmp/repro.c
clang-9:
~/src/llvm-project/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp:63: void
llvm::DeleteDeadBlocks(SmallVectorImpl<llvm::BasicBlock *> &,
llvm::DomTreeUpdater *): Assertion
`Dead.count(Pred) && "All predecessors must be dead!"' failed.
...
 #9 0x00007f448da1723b
llvm::DeleteDeadBlocks(llvm::SmallVectorImpl<llvm::BasicBlock*>&,
llvm::DomTreeUpdater*) ~/src
/llvm-project/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp:62:
5
#10 0x00007f448e5c67ab (anonymous
namespace)::ConstantTerminatorFoldingImpl::deleteDeadLoopBlocks()
~/src/llvm-project/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp:415:5

On Tue, Jan 22, 2019 at 9:43 AM Jordan Rupprecht <rupprecht at google.com>
wrote:

> It looks like this is still causing crashes, so I've temporarily reverted
> this as https://reviews.llvm.org/rL351845. I hope to have a repro later
> today.
>
> On Thu, Jan 17, 2019 at 9:01 PM Max Kazantsev via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: mkazantsev
>> Date: Thu Jan 17 20:57:32 2019
>> New Revision: 351520
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=351520&view=rev
>> Log:
>> Re-enable terminator folding in LoopSimplifyCFG: underlying bugs fixed
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=351520&r1=351519&r2=351520&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Thu Jan 17
>> 20:57:32 2019
>> @@ -42,7 +42,7 @@ using namespace llvm;
>>  #define DEBUG_TYPE "loop-simplifycfg"
>>
>>  static cl::opt<bool>
>> EnableTermFolding("enable-loop-simplifycfg-term-folding",
>> -                                       cl::init(false));
>> +                                       cl::init(true));
>>
>>  STATISTIC(NumTerminatorsFolded,
>>            "Number of terminators folded to unconditional branches");
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>
>
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