[PATCH] AsmWriter/Bitcode: Support specialized debug nodes

Duncan P. N. Exon Smith dexonsmith at apple.com
Thu Feb 12 16:07:41 PST 2015 

> On 2015-Feb-11, at 08:25, Adrian Prantl <aprantl at apple.com> wrote:
> 
>> 
>> On Feb 10, 2015, at 6:29 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
>> 
>>> 
>>> On 2015-Feb-10, at 16:59, Adrian Prantl <aprantl at apple.com> wrote:
>>> 
>>> 
>>>> On Feb 10, 2015, at 4:48 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
>>>> 
>>>> 
>>>>> On 2015-Feb-10, at 16:05, Adrian Prantl <aprantl at apple.com> wrote:
>>>>> 
>>>>> A few nitpicky suggestions and questions:
>>>>> 
>>>>> - !MDSubrange(count: 30, lo: 2)
>>>>> what about spelling out “low” and “high”?
>>>> 
>>>> It doesn't mean "low" and "high", though, right?  It means
>>>> "count"/"size" and "index of first element”.
>>> 
>>> You are probably right. I was thinking of DWARF where a subrange may either have a
>>> DW_AT_lower_bound and/or a DW_AT_upper_bound
>>> or a
>>> DW_AT_lower_bound and/or a DW_AT_count
>>> 
>>> We only support the second form so count and lower_bound would probably be most accurate.
>> 
>> Sounds good.  In keeping with the field naming convention I've adopted,
>> I'll use 'count:' and 'lowerBound:’.
> 
> yes, sure!
>> 
>>>> 
>>>> Or have I misinterpreted it?
>>>> 
>>>> How about "count" and "low"?
>>>> 
>>>>> 
>>>>> - do we still need the uniqueID on MDLexicalBlock? Could it be a distinct node instead?
>>>> 
>>>> I think this should be distinct instead.  I was planning to do this
>>>> as part of the upgrade (moving them into place).
>>>> 
>>>>> 
>>>>> - is it possible to have it print DW_OP-* constants such as in
>>>>> !MDExpression(DW_OP_deref, DW_OP_bit_piece, 0, 8)
>>>>> ?
>>>> 
>>>> I think this is pretty difficult the way that expressions are stored
>>>> right now -- it requires knowing how many arguments each thing takes,
>>>> etc.  In particular, how would the `AsmWriter` know whether something
>>>> should have a symbolic constant (`DW_OP_deref`) vs. being the number 6?
>>> 
>>> It would have to reuse the code from DIExpression::printInternal().
>> 
>> I think this is doable.
>> 
>> On the LLParser side, I've generally allowed raw ints (for `DW_TAG*`,
>> `DW_LANG*`, etc.), but for `DW_OP`s we could (at least for now) require
>> symbolic constants.
>> 
>>>> 
>>>> I was thinking of trying to clean this up later, but since we're
>>>> talking about it:
>>>> 
>>>> I think instead of `std::vector<uint64_t>` it should be
>>>> `std::vector<ExprOperand>`, where:
>>>> 
>>>> struct ExprOperand {
>>>>   LocationAtom Kind;
>>>>   unsigned NumArgs;
>>>>   uint64_t Args[2];
>>>>   ExprOperand(LocationAtom Kind);
>>>>   ExprOperand(LocationAtom Kind, uint64_t Arg);
>>>>   ExprOperand(LocationAtom Kind, uint64_t Arg1, uint64_t Arg2);
>>>> 
>>>>   static ExprOperand getDeref() {
>>>>     return ExprOperand(dwarf::DW_OP_deref);
>>>>   }
>>>>   static ExprOperand getPiece(uint64_t A1, uint64_t A2) {
>>>>     return ExprOperand(dwarf::DW_OP_bit_piece, A1, A2);
>>>>   }
>>>> };
>>>> 
>>>> ExprOperand Ops = {
>>>>   ExprOperand::getDeref(),
>>>>   ExprOperand::getPiece(0, 8)
>>>> };
>>>> auto *Expr = MDExpression::get(Ops);
>>>> 
>>>> Then the above could trivially be pretty-printed/parsed as:
>>>> 
>>>> !MDExpression(DW_OP_deref, DW_OP_bit_piece(0, 8))
>>> 
>>> or even better ... DW_OP_bit_piece(offset: 0, size: 8)
>> 
>> Sure.
>> 
>>> Yeah that looks good. Also we would need to introduce DW_OP_constu and get rid of the pseudo argument that DW_OP_plus currently takes.
>> 
>> Not necessary.  You can represent this already with:
>> 
>>   DW_OP_plus(7)
>> 
>> where `7` is the pseudo-argument.  This is somewhat horrible, but
>> so is `DW_OP_plus` taking a pseudo-argument ;).
>> 
>>> This doesn’t need to happen right away, but we should keep it in mind.
>> 
>> I think something like this would simplify the logic a lot, besides
>> making it more extensible.
>> 
>>>> 
>>>> Thoughts?
>>>> 
>>>> 
>>>>> 
>>>>> Will it still print the old-style comments that testcases tend to match on, or are they obsoleted by the human-readable syntax?
>>>> 
>>>> They're obsoleted.  The old-style comments will get stale and just
>>>> add noise.  If we've regressed somehow let me know how.
>>> 
>>> See my comment on DW_OP_bit_piece above :-)
>>> 
>> 
>> Hah, right, right :).
>> 
>> I'll see if I can get something together for you.  If not we can keep
>> the DW_TAG_expression comments temporarily.
>> 
>> Is it alright to lose the "offset=" and "size=" markers (at least
>> temporarily)?  I don't see a natural place to put them in the syntax.
>> E.g., I was thinking I'd aim for the following for now:
>> 
>>   !MDExpression(DW_OP_deref, DW_OP_plus, 8, DW_OP_bit_piece, 0, 8)
>> 
>> (and with no comment).  Is this sufficient?
> 
> Sufficient as an intermediate step on our way to the above expression being written as
> 
>  !MDExpression(DW_OP_deref, DW_OP_constu(8), DW_OP_plus, DW_OP_bit_piece(offset: 0, size: 8))

Yup, although I'm happy for someone else to drive that -- the biggest
change will be switching to `DW_OP_constu`.  Once that's done I can
do the assembly if you want.

Attached a new set of patches (included the full series for reference).
The ones you probably want to look at are:

  - 0001/0002: getOperationEncoding().
  - 0003: Porting the DIExpression logic over.  I did a few things
    differently since the base iterator is random access.
  - 0021: MDExpression.

I'll start pushing through the others while you take a look at the
changes.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: all.patch
Type: application/octet-stream
Size: 154798 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment.obj>
-------------- next part --------------


-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-Support-Rewrite-LocationAtom-and-OperationEncodingSt.patch
Type: application/octet-stream
Size: 21487 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0001.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0002-Support-Add-dwarf-getOperationEncoding.patch
Type: application/octet-stream
Size: 2537 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0003-IR-Add-MDExpression-ExprOperand.patch
Type: application/octet-stream
Size: 7141 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0003.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0004-AsmWriter-Bitcode-MDSubrange.patch
Type: application/octet-stream
Size: 11152 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0004.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0005-AsmWriter-Bitcode-MDEnumerator.patch
Type: application/octet-stream
Size: 7999 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0005.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0006-AsmWriter-Bitcode-MDBasicType.patch
Type: application/octet-stream
Size: 8584 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0006.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0007-AsmWriter-MDBasicType-Recognize-DW_ATE-in-encoding.patch
Type: application/octet-stream
Size: 6415 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0007.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0008-AsmWriter-Bitcode-MDFile.patch
Type: application/octet-stream
Size: 9072 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0008.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0009-AsmWriter-Bitcode-MDDerivedType-and-MDCompositeType.patch
Type: application/octet-stream
Size: 20323 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0009.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0010-AsmWriter-MDCompositeType-Recognize-DW_LANG-in-runti.patch
Type: application/octet-stream
Size: 10395 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0010.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0011-AsmWriter-Bitcode-MDSubroutineType.patch
Type: application/octet-stream
Size: 7243 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0011.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0012-AsmWriter-Bitcode-MDCompileUnit.patch
Type: application/octet-stream
Size: 14341 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0012.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0013-AsmWriter-Bitcode-MDSubprogram.patch
Type: application/octet-stream
Size: 16550 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0013.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0014-AsmWriter-MDSubprogram-Recognize-DW_VIRTUALITY-in-vi.patch
Type: application/octet-stream
Size: 7445 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0014.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0015-AsmWriter-Bitcode-MDLexicalBlock.patch
Type: application/octet-stream
Size: 7549 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0015.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0016-AsmWriter-Bitcode-MDLexicalBlockFile.patch
Type: application/octet-stream
Size: 8619 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0016.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0017-AsmWriter-Bitcode-MDNamespace.patch
Type: application/octet-stream
Size: 8155 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0017.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0018-AsmWriter-Bitcode-MDTemplate-Type-Value-Parameter.patch
Type: application/octet-stream
Size: 16402 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0018.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0019-AsmWriter-Bitcode-MDGlobalVariable.patch
Type: application/octet-stream
Size: 11299 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0019.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0020-AsmWriter-Bitcode-MDLocalVariable.patch
Type: application/octet-stream
Size: 10779 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0020.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0021-AsmWriter-Bitcode-MDExpression.patch
Type: application/octet-stream
Size: 10629 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0021.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0022-AsmWriter-Bitcode-MDObjCProperty.patch
Type: application/octet-stream
Size: 9569 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0022.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0023-AsmWriter-Bitcode-MDImportedEntity.patch
Type: application/octet-stream
Size: 9143 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150212/356d53f2/attachment-0023.obj>

More information about the llvm-commits mailing list