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[ThinLTO] Auto-hide prevailing linkonce_odr only when all copies eligible

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Summary:
We hit undefined references building with ThinLTO when one source file
contained explicit instantiations of a template method (weak_odr) but
there were also implicit instantiations in another file (linkonce_odr),
and the latter was the prevailing copy. In this case the symbol was
marked hidden when the prevailing linkonce_odr copy was promoted to
weak_odr. It led to unsats when the resulting shared library was linked
with other code that contained a reference (expecting to be resolved due
to the explicit instantiation).

Add a CanAutoHide flag to the GV summary to allow the thin link to
identify when all copies are eligible for auto-hiding (because they were
all originally linkonce_odr global unnamed addr), and only do the
auto-hide in that case.

Most of the changes here are due to plumbing the new flag through the
bitcode and llvm assembly, and resulting test changes. I augmented the
existing auto-hide test to check for this situation.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, dexonsmith, arphaman, dang, llvm-commits, steven_wu, wmi

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59709

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360466 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Teresa Johnson
2019-05-10 20:08:24 +00:00
parent 354c14e139
commit 9488ca4c3f
29 changed files with 280 additions and 138 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/Analysis/ModuleSummaryAnalysis.cpp
+8 -4
View File
@@ -391,7 +391,8 @@ static void computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
bool NotEligibleForImport =
NonRenamableLocal || HasInlineAsmMaybeReferencingInternal;
GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
/* Live = */ false, F.isDSOLocal());
/* Live = */ false, F.isDSOLocal(),
F.hasLinkOnceODRLinkage() && F.hasGlobalUnnamedAddr());
FunctionSummary::FFlags FunFlags{
F.hasFnAttribute(Attribute::ReadNone),
F.hasFnAttribute(Attribute::ReadOnly),
@@ -418,7 +419,8 @@ computeVariableSummary(ModuleSummaryIndex &Index, const GlobalVariable &V,
bool HasBlockAddress = findRefEdges(Index, &V, RefEdges, Visited);
bool NonRenamableLocal = isNonRenamableLocal(V);
GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
/* Live = */ false, V.isDSOLocal());
/* Live = */ false, V.isDSOLocal(),
V.hasLinkOnceODRLinkage() && V.hasGlobalUnnamedAddr());
// Don't mark variables we won't be able to internalize as read-only.
GlobalVarSummary::GVarFlags VarFlags(
@@ -438,7 +440,8 @@ computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
DenseSet<GlobalValue::GUID> &CantBePromoted) {
bool NonRenamableLocal = isNonRenamableLocal(A);
GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
/* Live = */ false, A.isDSOLocal());
/* Live = */ false, A.isDSOLocal(),
A.hasLinkOnceODRLinkage() && A.hasGlobalUnnamedAddr());
auto AS = llvm::make_unique<AliasSummary>(Flags);
auto *Aliasee = A.getBaseObject();
auto AliaseeVI = Index.getValueInfo(Aliasee->getGUID());
@@ -513,7 +516,8 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
/* NotEligibleToImport = */ true,
/* Live = */ true,
/* Local */ GV->isDSOLocal());
/* Local */ GV->isDSOLocal(),
GV->hasLinkOnceODRLinkage() && GV->hasGlobalUnnamedAddr());
CantBePromoted.insert(GV->getGUID());
// Create the appropriate summary type.
if (Function *F = dyn_cast<Function>(GV)) {