[llvm-dev] Should we split llvm Support and ADT?

Hal Finkel via llvm-dev
Sat, 27 May 2017 01:48:26 -0000

On 05/26/2017 07:59 PM, Zachary Turner wrote:
> It's that TableGen depends on Support, so if you change one file in
> support, support gets recompiled into a new static archive, which
> triggers a rerun of tablegen on all the tablegen inputs, which is
> extremely slow.

I thought that we had a "build an optimized tablegen even in debug
mode"
setting to work around this problem. Would that avoid this problem?

  -Hal

>
> On Fri, May 26, 2017 at 5:56 PM Hal Finkel <hfinkel at anl.gov
> <mailto:hfinkel at anl.gov>> wrote:
>
>
>
>     On 05/26/2017 07:47 PM, Zachary Turner via llvm-dev wrote:
>>     Changing a header file somewhere and having to spend 10 minutes
>>     waiting for a build leads to a lot of wasted developer time.
>>
>>     The real culprit here is tablegen.  Can we split support and ADT
>>     into two - the parts that tablegen depends on and the parts that
>>     it doesn't?
>
>     What's the actual problem here? Is it that TableGen regenerates
>     different files and so we then need to rebuild all dependencies of
>     those files? Maybe we should use a diff-and-update approach (I
>     thought, however, that we already did that).
>
>      -Hal
>
>>
>>     From what I can gather, Tablegen currently depends on these
>>     headers and all of their transitive dependencies.
>>
>>     #include "llvm/Support/Casting.h"
>>     #include "llvm/Support/CommandLine.h"
>>     #include "llvm/Support/Compiler.h"
>>     #include "llvm/Support/DataTypes.h"
>>     #include "llvm/Support/Debug.h"
>>     #include "llvm/Support/Error.h"
>>     #include "llvm/Support/ErrorHandling.h"
>>     #include "llvm/Support/Format.h"
>>     #include "llvm/Support/FormattedStream.h"
>>     #include "llvm/Support/LEB128.h"
>>     #include "llvm/Support/LowLevelTypeImpl.h"
>>     #include "llvm/Support/ManagedStatic.h"
>>     #include "llvm/Support/MathExtras.h"
>>     #include "llvm/Support/MemoryBuffer.h"
>>     #include "llvm/Support/PrettyStackTrace.h"
>>     #include "llvm/Support/Regex.h"
>>     #include "llvm/Support/SMLoc.h"
>>     #include "llvm/Support/ScopedPrinter.h"
>>     #include "llvm/Support/Signals.h"
>>     #include "llvm/Support/SourceMgr.h"
>>     #include "llvm/Support/raw_ostream.h"
>>
>>     #include "llvm/ADT/APInt.h"
>>     #include "llvm/ADT/ArrayRef.h"
>>     #include "llvm/ADT/BitVector.h"
>>     #include "llvm/ADT/CachedHashString.h"
>>     #include "llvm/ADT/DenseSet.h"
>>     #include "llvm/ADT/IndexedMap.h"
>>     #include "llvm/ADT/IntEqClasses.h"
>>     #include "llvm/ADT/MapVector.h"
>>     #include "llvm/ADT/Optional.h"
>>     #include "llvm/ADT/PointerUnion.h"
>>     #include "llvm/ADT/STLExtras.h"
>>     #include "llvm/ADT/SetVector.h"
>>     #include "llvm/ADT/SmallPtrSet.h"
>>     #include "llvm/ADT/SmallSet.h"
>>     #include "llvm/ADT/SmallVector.h"
>>     #include "llvm/ADT/SparseBitVector.h"
>>     #include "llvm/ADT/Statistic.h"
>>     #include "llvm/ADT/StringExtras.h"
>>     #include "llvm/ADT/StringMap.h"
>>     #include "llvm/ADT/StringRef.h"
>>     #include "llvm/ADT/StringSet.h"
>>     #include "llvm/ADT/StringSwitch.h"
>>     #include "llvm/ADT/TinyPtrVector.h"
>>     #include "llvm/ADT/Twine.h"
>>
>>
>>     Is this something worth putting effort into?  If so, I volunteer.
>>
>>
>>
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>
>     --
>     Hal Finkel
>     Lead, Compiler Technology and Programming Languages
>     Leadership Computing Facility
>     Argonne National Laboratory
>

--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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