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

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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

llvm-svn: 292420
This commit is contained in:
Mehdi Amini 2017-01-18 18:36:21 +00:00
parent 88cd0769ca
commit acf5525670
2 changed files with 20 additions and 7 deletions
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21
lib/Bitcode/Reader/MetadataLoader.cpp
View File

@ -768,13 +768,12 @@ void MetadataLoader::MetadataLoaderImpl::lazyLoadOneMetadata(
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::parseOneMetadata(
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);

6
test/ThinLTO/X86/lazyload_metadata.ll
View File

@ -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}