[llvm] r312165 - Refactor DIBuilder::createFragmentExpression into a static DIExpression member

[Adrian Prantl via llvm-commits]

> On Oct 30, 2017, at 2:25 PM, Francois Pichet <pichet2000 at gmail.com> wrote:
> 
> 
> 
> On Mon, Oct 30, 2017 at 5:15 PM, Adrian Prantl <aprantl at apple.com <mailto:aprantl at apple.com>> wrote:
> 
> 
>> On Oct 30, 2017, at 2:12 PM, Francois Pichet <pichet2000 at gmail.com <mailto:pichet2000 at gmail.com>> wrote:
>> 
>> 
>> 
>> On Wed, Aug 30, 2017 at 4:04 PM, Adrian Prantl via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>> Author: adrian
>> Date: Wed Aug 30 13:04:17 2017
>> New Revision: 312165
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=312165&view=rev <http://llvm.org/viewvc/llvm-project?rev=312165&view=rev>
>> Log:
>> Refactor DIBuilder::createFragmentExpression into a static DIExpression member
>> 
>> NFC
>> 
>> Modified:
>>     llvm/trunk/include/llvm/IR/DIBuilder.h
>>     llvm/trunk/include/llvm/IR/DebugInfoMetadata.h
>>     llvm/trunk/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
>>     llvm/trunk/lib/IR/DIBuilder.cpp
>>     llvm/trunk/lib/IR/DebugInfoMetadata.cpp
>>     llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
>>     llvm/trunk/lib/Transforms/Scalar/SROA.cpp
>> 
>> 
>> 
>> Modified: llvm/trunk/lib/IR/DebugInfoMetadata.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfoMetadata.cpp?rev=312165&r1=312164&r2=312165&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfoMetadata.cpp?rev=312165&r1=312164&r2=312165&view=diff>
>> ==============================================================================
>> --- llvm/trunk/lib/IR/DebugInfoMetadata.cpp (original)
>> +++ llvm/trunk/lib/IR/DebugInfoMetadata.cpp Wed Aug 30 13:04:17 2017
>> @@ -724,6 +724,34 @@ DIExpression *DIExpression::prepend(cons
>>    return DIExpression::get(Expr->getContext(), Ops);
>>  }
>> 
>> +DIExpression *DIExpression::createFragmentExpression(const DIExpression *Expr,
>> +                                                     unsigned OffsetInBits,
>> +                                                     unsigned SizeInBits) {
>> +  SmallVector<uint64_t, 8> Ops;
>> +  // Copy over the expression, but leave off any trailing DW_OP_LLVM_fragment.
>> +  if (Expr) {
>> +    for (auto Op : Expr->expr_ops()) {
>> +      if (Op.getOp() == dwarf::DW_OP_LLVM_fragment) {
>> +        // Make the new offset point into the existing fragment.
>> +        uint64_t FragmentOffsetInBits = Op.getArg(0);
>> +        // Op.getArg(0) is FragmentOffsetInBits.
>> +        // Op.getArg(1) is FragmentSizeInBits.
>> +        assert((OffsetInBits + SizeInBits <= Op.getArg(0) + Op.getArg(1)) &&
>> +               "new fragment outside of original fragment");
>> 
>> 
>>  Hi, 
>> 
>> I am getting an assert here on an (out of tree) big-endian target where 64-bit variables are splitted on 2 32-bit variables.
>> assert where: OffsetInBits=32, SizeInBits=32 and Expr: !DIExpression(DW_OP_LLVM_fragment, 0, 32)
>> so 32 + 32 <= 32 is not true.
>> 
>> I might be wrong but I think the assert is only valid on little endian target?
> 
> I'm not sure I understand your example. Are you saying that you are calling createFragmentExpression on something that is already 32-bit fragment? Which pass is calling it? It seems more likely that there is something wrong with the call site.
> 
> -- adrian
> 
> 
> DAGTypeLegalizer::SetExpandedInteger is the call site:
> 
createFragmentExpression creates a fragment of and existing value at a given offset, and with a given size. If the existing value already is a fragment the offset and size are *within* the existing fragment. The assert verifies this. It should be endianness-neutral. Can you explain why you believe the assertion is wrong for big-endian targets?


>   if (DAG.getDataLayout().isBigEndian()) {
>     transferDbgValues(DAG, Op, Hi, 0);
>     transferDbgValues(DAG, Op, Lo, Hi.getValueSizeInBits());  // <--- assert 

This code was added in https://reviews.llvm.org/D38172 <https://reviews.llvm.org/D38172>. This is splitting the debug info into one part describing the Hi bits (at offset 0) and the Lo bits (at sizeof(Hi)). Since you are seeing the assertion I assume that you have a value that is split twice, is that correct? Can you explain why createFragmentExpression is called with a !DIExpression(DW_OP_LLVM_fragment, 0, 32)?

thanks,
adrian

>   } else {
>     transferDbgValues(DAG, Op, Lo, 0);
>     transferDbgValues(DAG, Op, Hi, Lo.getValueSizeInBits());
>   }
> 
> The first call to transferDbgValues will create !DIExpression(DW_OP_LLVM_fragment, 0, 32)
> The second call will assert because OffsetInBits= 32 and SizeInBits=32
> 
> I believe the assert is only valid on little-endian target. 


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