[llvm] 0581c0b - Revert "[SCEV] Look through single value PHIs."

[Florian Hahn via llvm-commits]

> On Aug 13, 2020, at 07:19, Ali Tamur via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> 
> Author: Ali Tamur
> Date: 2020-08-12T23:13:24-07:00
> New Revision: 0581c0b0eeba03da590d1176a4580cf9b9e8d1e3
> 
> URL: https://github.com/llvm/llvm-project/commit/0581c0b0eeba03da590d1176a4580cf9b9e8d1e3
> DIFF: https://github.com/llvm/llvm-project/commit/0581c0b0eeba03da590d1176a4580cf9b9e8d1e3.diff
> 
> LOG: Revert "[SCEV] Look through single value PHIs."
> 
> This reverts commit e441b7a7a0a72c28daf5a8e594559c667e5b4534.
> 
> This patch causes a compile error in tensorflow opensource project. The stack trace looks like:
> 
> Point of crash:
> llvm/include/llvm/Analysis/LoopInfoImpl.h : line 35
> 
> (gdb) ptype *this
> type = const class llvm::LoopBase<llvm::BasicBlock, llvm::Loop> [with BlockT = llvm::BasicBlock, LoopT = llvm::Loop]
> 
> (gdb) p *this
> $1 = {ParentLoop = 0x0, SubLoops = std::vector of length 0, capacity 0, Blocks = std::vector of length 0, capacity 1,
>  DenseBlockSet = {<llvm::SmallPtrSetImpl<llvm::BasicBlock const*>> = {<llvm::SmallPtrSetImplBase> = {<llvm::DebugEpochBase> = {Epoch = 3}, SmallArray = 0x1b2bf6c8, CurArray = 0x1b2bf6c8,
>        CurArraySize = 8, NumNonEmpty = 0, NumTombstones = 0}, <No data fields>}, SmallStorage = {0xfffffffffffffffe, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}}, IsInvalid = true}
> 
> (gdb) p *this->DenseBlockSet->CurArray
> $2 = (const void *) 0xfffffffffffffffe
> 
> I will try to get a case from tensorflow or use creduce to get a small case.
> 

That would be great, thank you. Additionally, the full backtrace might also be helpful, as it is not clear which pass causes the crash.

Cheers,
Florian