llvm dev - Aug 2018 - [DebugInfo] DIBuilder missing interface to generate DWARF info for packed_decimal basic type.

Adding tags on subject line

From: Chirag Patel
Sent: 22 August 2018 11:20
To: llvm-dev at lists.llvm.org
Subject: DIBuilder missing interface to generate DWARF info for packed_decimal
basic type.

Hello,

I am working on a llvm based compiler frontend in which, I am using the
packed_decimal type encoding.

During using the llvm DIBuilder, I found out that the interface to create
BasicType with packed_decimal encoding(DW_ATE_packed_decimal), is missing all
the related encoding stuff,
Like
(Missing)
               DW_AT_picture_string - should be MDString Node - not decided yet.
               DW_AT_decimal_sign - May be in DIflags with mask (5 distinct
inputs), like FlagDSOverPunch, etc
               DW_AT_digit_count - unsigned integer, like unsigned DigitCount
               DW_AT_decimal_scale - integer, like int DecimalScale

I am looking to add this info in DIBasicType class (DebugInfoMetadata.h) and
would appreciate advice on above location.

Regrads,

Chirag Patel| Software Engineer
RAINCODE Mainframe to .NET
Tel : +91 080 41159811 | Mob : +91 90493 36744
www.raincodelabs.com<http://www.raincodelabs.com/>

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Hi Chirag,

The DW_ATE_packed_decimal (etc) constants exist because they are merely
additional values in an enumeration, and we just added all the values defined in
DWARF to the enumeration .  LLVM does not actually support any of the decimal
types, or scaled binary types.  (Somebody is actively working on scaled binary
operations, although they have not yet gotten to the point of wanting to support
debug info.)

Without spending much time thinking about it, my inclination would be to add a
new method to DIBuilder for the decimal and scaled binary types, because the
additional parameters are meaningless in any other context.  You might also
consider whether to add a separate subclass of DIBasicType to handling scaling
and decimal attributes.  The decimal and scaled types are quite unusual, and we
would not want to impose additional memory cost on all basic types to support
these relatively rare cases.

Are you planning to support all the decimal types?  I know the OpenVMS people
will also want them, for COBOL and other languages, so there's benefit in
having proper support in LLVM.  But even if you are interested only in packed
decimal, the infrastructure ought to be designed to handle all cases.

Thanks,
--paulr
(who helped design the DWARF support for COBOL types a long time ago)

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Chirag
Patel via llvm-dev
Sent: Wednesday, August 22, 2018 2:10 AM
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] [DebugInfo] DIBuilder missing interface to generate DWARF
info for packed_decimal basic type.

Adding tags on subject line

From: Chirag Patel
Sent: 22 August 2018 11:20
To: llvm-dev at lists.llvm.org
Subject: DIBuilder missing interface to generate DWARF info for packed_decimal
basic type.

Hello,

I am working on a llvm based compiler frontend in which, I am using the
packed_decimal type encoding.

During using the llvm DIBuilder, I found out that the interface to create
BasicType with packed_decimal encoding(DW_ATE_packed_decimal), is missing all
the related encoding stuff,
Like
(Missing)
               DW_AT_picture_string - should be MDString Node - not decided yet.
               DW_AT_decimal_sign - May be in DIflags with mask (5 distinct
inputs), like FlagDSOverPunch, etc
               DW_AT_digit_count - unsigned integer, like unsigned DigitCount
               DW_AT_decimal_scale - integer, like int DecimalScale

I am looking to add this info in DIBasicType class (DebugInfoMetadata.h) and
would appreciate advice on above location.

Regrads,

Chirag Patel| Software Engineer
RAINCODE Mainframe to .NET
Tel : +91 080 41159811 | Mob : +91 90493 36744
www.raincodelabs.com<http://www.raincodelabs.com/>

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Hello Paul,

Thanks for the reply.
Yes, I am only looking for dwarf support at the moment and planning to support
both PLI/COBOL decimal types. Also thanks for the suggestion, you are right as
it is going to be rare cases, so it will be better to implement a separate
subclass to avoid memory overhead for others.
>>  (Somebody is actively working on scaled binary operations, although
they have not yet gotten to the point of wanting to support debug info.)
If possible, can you kindly get me in touch with them so I would not spend time
on which is already been done?

Regards,

Chirag Patel| Software Engineer
RAINCODE Mainframe to .NET
Tel : +91 080 41159811 | Mob : +91 90493 36744
www.raincodelabs.com<http://www.raincodelabs.com/>

From: paul.robinson at sony.com <paul.robinson at sony.com>
Sent: 22 August 2018 23:03
To: Chirag Patel <Chirag at raincode.com>
Cc: llvm-dev at lists.llvm.org
Subject: RE: [llvm-dev] [DebugInfo] DIBuilder missing interface to generate
DWARF info for packed_decimal basic type.

Hi Chirag,

The DW_ATE_packed_decimal (etc) constants exist because they are merely
additional values in an enumeration, and we just added all the values defined in
DWARF to the enumeration .  LLVM does not actually support any of the decimal
types, or scaled binary types.  (Somebody is actively working on scaled binary
operations, although they have not yet gotten to the point of wanting to support
debug info.)

Without spending much time thinking about it, my inclination would be to add a
new method to DIBuilder for the decimal and scaled binary types, because the
additional parameters are meaningless in any other context.  You might also
consider whether to add a separate subclass of DIBasicType to handling scaling
and decimal attributes.  The decimal and scaled types are quite unusual, and we
would not want to impose additional memory cost on all basic types to support
these relatively rare cases.

Are you planning to support all the decimal types?  I know the OpenVMS people
will also want them, for COBOL and other languages, so there's benefit in
having proper support in LLVM.  But even if you are interested only in packed
decimal, the infrastructure ought to be designed to handle all cases.

Thanks,
--paulr
(who helped design the DWARF support for COBOL types a long time ago)

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Chirag
Patel via llvm-dev
Sent: Wednesday, August 22, 2018 2:10 AM
To: llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: [llvm-dev] [DebugInfo] DIBuilder missing interface to generate DWARF
info for packed_decimal basic type.

Adding tags on subject line

From: Chirag Patel
Sent: 22 August 2018 11:20
To: llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: DIBuilder missing interface to generate DWARF info for packed_decimal
basic type.

Hello,

I am working on a llvm based compiler frontend in which, I am using the
packed_decimal type encoding.

During using the llvm DIBuilder, I found out that the interface to create
BasicType with packed_decimal encoding(DW_ATE_packed_decimal), is missing all
the related encoding stuff,
Like
(Missing)
               DW_AT_picture_string - should be MDString Node - not decided yet.
               DW_AT_decimal_sign - May be in DIflags with mask (5 distinct
inputs), like FlagDSOverPunch, etc
               DW_AT_digit_count - unsigned integer, like unsigned DigitCount
               DW_AT_decimal_scale - integer, like int DecimalScale

I am looking to add this info in DIBasicType class (DebugInfoMetadata.h) and
would appreciate advice on above location.

Regrads,

Chirag Patel| Software Engineer
RAINCODE Mainframe to .NET
Tel : +91 080 41159811 | Mob : +91 90493 36744
www.raincodelabs.com<http://www.raincodelabs.com/>

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