[llvm] r292420 - [ThinLTO] Add a recursive step in Metadata lazy-loading

[Peter Collingbourne via llvm-commits]

Approved.

Peter

On Wed, Jan 18, 2017 at 10:51 AM, Mehdi Amini <mehdi.amini at apple.com> wrote:

> Hi Peter,
>
> I’d like to cherry-pick this into the 4.0 release. This is a follow-up to
> r291027, it achieve what was originally promised.
>
> It will only affect ThinLTO, as lazy-loading happens only there.
>
> Thanks,
>
> —
> Mehdi
>
> > On Jan 18, 2017, at 10:36 AM, Mehdi Amini via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
> >
> > Author: mehdi_amini
> > Date: Wed Jan 18 12:36:21 2017
> > New Revision: 292420
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=292420&view=rev
> > Log:
> > [ThinLTO] Add a recursive step in Metadata lazy-loading
> >
> > Summary:
> > Without this, we're stressing the RAUW of unique nodes,
> > which is a costly operation. This is intended to limit
> > the number of RAUW, and is very effective on the total
> > link-time of opt with ThinLTO, before:
> >
> >  real 4m4.587s  user 15m3.401s  sys 0m23.616s
> >
> > after:
> >
> >  real 3m25.261s user 12m22.132s sys 0m24.152s
> >
> > Reviewers: tejohnson, pcc
> >
> > Subscribers: llvm-commits
> >
> > Differential Revision: https://reviews.llvm.org/D28751
> >
> > Modified:
> >    llvm/trunk/lib/Bitcode/Reader/MetadataLoader.cpp
> >    llvm/trunk/test/ThinLTO/X86/lazyload_metadata.ll
> >
> > Modified: llvm/trunk/lib/Bitcode/Reader/MetadataLoader.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> Bitcode/Reader/MetadataLoader.cpp?rev=292420&r1=292419&r2=292420&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/lib/Bitcode/Reader/MetadataLoader.cpp (original)
> > +++ llvm/trunk/lib/Bitcode/Reader/MetadataLoader.cpp Wed Jan 18
> 12:36:21 2017
> > @@ -768,13 +768,12 @@ void MetadataLoader::MetadataLoaderImpl:
> >     unsigned ID, PlaceholderQueue &Placeholders) {
> >   assert(ID < (MDStringRef.size()) + GlobalMetadataBitPosIndex.size());
> >   assert(ID >= MDStringRef.size() && "Unexpected lazy-loading of
> MDString");
> > -#ifndef NDEBUG
> >   // Lookup first if the metadata hasn't already been loaded.
> >   if (auto *MD = MetadataList.lookup(ID)) {
> >     auto *N = dyn_cast_or_null<MDNode>(MD);
> > -    assert(N && N->isTemporary() && "Lazy loading an already loaded
> metadata");
> > +    if (!N->isTemporary())
> > +      return;
> >   }
> > -#endif
> >   SmallVector<uint64_t, 64> Record;
> >   StringRef Blob;
> >   IndexCursor.JumpToBit(GlobalMetadataBitPosIndex[ID -
> MDStringRef.size()]);
> > @@ -827,8 +826,22 @@ Error MetadataLoader::MetadataLoaderImpl
> >   auto getMD = [&](unsigned ID) -> Metadata * {
> >     if (ID < MDStringRef.size())
> >       return lazyLoadOneMDString(ID);
> > -    if (!IsDistinct)
> > +    if (!IsDistinct) {
> > +      if (auto *MD = MetadataList.lookup(ID))
> > +        return MD;
> > +      // If lazy-loading is enabled, we try recursively to load the
> operand
> > +      // instead of creating a temporary.
> > +      if (ID < (MDStringRef.size() + GlobalMetadataBitPosIndex.size()))
> {
> > +        // Create a temporary for the node that is referencing the
> operand we
> > +        // will lazy-load. It is needed before recursing in case there
> are
> > +        // uniquing cycles.
> > +        MetadataList.getMetadataFwdRef(NextMetadataNo);
> > +        lazyLoadOneMetadata(ID, Placeholders);
> > +        return MetadataList.lookup(ID);
> > +      }
> > +      // Return a temporary.
> >       return MetadataList.getMetadataFwdRef(ID);
> > +    }
> >     if (auto *MD = MetadataList.getMetadataIfResolved(ID))
> >       return MD;
> >     return &Placeholders.getPlaceholderOp(ID);
> >
> > Modified: llvm/trunk/test/ThinLTO/X86/lazyload_metadata.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> ThinLTO/X86/lazyload_metadata.ll?rev=292420&r1=292419&r2=292420&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/test/ThinLTO/X86/lazyload_metadata.ll (original)
> > +++ llvm/trunk/test/ThinLTO/X86/lazyload_metadata.ll Wed Jan 18
> 12:36:21 2017
> > @@ -17,7 +17,7 @@
> > ; RUN:          -o /dev/null -disable-ondemand-mds-loading -stats \
> > ; RUN:  2>&1 | FileCheck %s -check-prefix=NOTLAZY
> > ; NOTLAZY: 58 bitcode-reader  - Number of Metadata records loaded
> > -; NOTLAZY: 8 bitcode-reader  - Number of MDStrings loaded
> > +; NOTLAZY: 6 bitcode-reader  - Number of MDStrings loaded
> >
> >
> > target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
> > @@ -48,7 +48,7 @@ define void @globalfunc3(i32 %arg) {
> > !3 = !{!"3"}
> > !4 = !{!"4"}
> > !5 = !{!"5"}
> > -!6 = !{!"6"}
> > +!6 = !{!9}
> > !7 = !{!"7"}
> > !8 = !{!"8"}
> > -!9 = !{!"9"}
> > +!9 = !{!6}
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
>


-- 
-- 
Peter
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