[llvm] r297971 - Salvage debug info from instructions about to be deleted

[Adrian Prantl via llvm-commits]

Reverted in r297982.

-- adrian
> On Mar 16, 2017, at 1:18 PM, Evgenii Stepanov <eugeni.stepanov at gmail.com> wrote:
> 
> I can confirm the reverting this change helps. Would you mind doing
> that? It's pretty bad, check-msan just nearly killed my machine.
> 
> I'm working on a test case.
> 
> On Thu, Mar 16, 2017 at 1:15 PM, Adrian Prantl <aprantl at apple.com> wrote:
>> Is there a bot that catches this or otherwise any instructions to reproduce this?
>> 
>> thanks,
>> adrian
>> 
>>> On Mar 16, 2017, at 1:13 PM, Evgenii Stepanov <eugeni.stepanov at gmail.com> wrote:
>>> 
>>> Hi,
>>> 
>>> ninja check-msan on linux/x86_64 has started using unlimited memory
>>> and I suspect this change.
>>> One common allocation is
>>> 
>>> #9 0x00007f40f6cfae0d operator new(unsigned long)
>>> /build/gcc-4.8-mW1ufQ/gcc-4.8-4.8.4/build/x86_64-linux-gnu/libstdc++-v3/libsupc++/../../../../src/libstdc++-v3/libsupc++/new_op.cc:56:0
>>> #10 0x00000000017e3a8d llvm::DIExpression::getImpl(llvm::LLVMContext&,
>>> llvm::ArrayRef<unsigned long>, llvm::Metadata::StorageType, bool)
>>> (/code/build-llvm/bin/clang-5.0+0x17e3a8d)
>>> #11 0x0000000001dae195 prependDIExpr(llvm::DIBuilder&,
>>> llvm::DIExpression*, bool, long)
>>> (/code/build-llvm/bin/clang-5.0+0x1dae195)
>>> #12 0x0000000001db539b std::_Function_handler<void
>>> (llvm::DbgValueInst&),
>>> llvm::salvageDebugInfo(llvm::Instruction&)::$_2>::_M_invoke(std::_Any_data
>>> const&, llvm::DbgValueInst&)
>>> (/code/build-llvm/bin/clang-5.0+0x1db539b)
>>> #13 0x0000000001dade35 llvm::findDbgValues(llvm::Value*,
>>> std::function<void (llvm::DbgValueInst&)>)
>>> (/code/build-llvm/bin/clang-5.0+0x1dade35)
>>> #14 0x0000000001dae7f6 llvm::salvageDebugInfo(llvm::Instruction&)
>>> (/code/build-llvm/bin/clang-5.0+0x1dae7f6)
>>> #15 0x0000000001961964
>>> llvm::InstCombiner::eraseInstFromFunction(llvm::Instruction&)
>>> (/code/build-llvm/bin/clang-5.0+0x1961964)
>>> #16 0x000000000196deb5 llvm::InstCombiner::run()
>>> (/code/build-llvm/bin/clang-5.0+0x196deb5)
>>> 
>>> 
>>