[PGO] Use linkonce_odr linkage for __profd_ variables in comdat groups
This fixes relocations against __profd_ symbols in discarded sections,
which is PR41380.
In general, instrumentation happens very early, and optimization and
inlining happens afterwards. The counters for a function are calculated
early, and after inlining, counters for an inlined function may be
widely referenced by other functions.
For C++ inline functions of all kinds (linkonce_odr &
available_externally mainly), instr profiling wants to deduplicate these
__profc_ and __profd_ globals. Otherwise the binary would be quite
large.
I made __profd_ and __profc_ comdat in r355044, but I chose to make
__profd_ internal. At the time, I was only dealing with coverage, and in
that case, none of the instrumentation needs to reference __profd_.
However, if you use PGO, then instrumentation passes add calls to
__llvm_profile_instrument_range which reference __profd_ globals. The
solution is to make these globals externally visible by using
linkonce_odr linkage for data as was done for counters.
This is safe because PGO adds a CFG hash to the names of the data and
counter globals, so if different TUs have different globals, they will
get different data and counter arrays.
Reviewers: xur, hans
Differential Revision: https://reviews.llvm.org/D67579
llvm-svn: 372020
diff --git a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
index a21604a..65773bb 100644
--- a/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
@@ -740,9 +740,8 @@
PD = It->second;
}
- // Match the linkage and visibility of the name global, except on COFF, where
- // the linkage must be local and consequentially the visibility must be
- // default.
+ // Match the linkage and visibility of the name global. COFF supports using
+ // comdats with internal symbols, so do that if we can.
Function *Fn = Inc->getParent()->getParent();
GlobalValue::LinkageTypes Linkage = NamePtr->getLinkage();
GlobalValue::VisibilityTypes Visibility = NamePtr->getVisibility();
@@ -759,15 +758,16 @@
// of the parent function, that will result in relocations against discarded
// sections.
Comdat *Cmdt = nullptr;
- GlobalValue::LinkageTypes CounterLinkage = Linkage;
if (needsComdatForCounter(*Fn, *M)) {
StringRef CmdtPrefix = getInstrProfComdatPrefix();
if (TT.isOSBinFormatCOFF()) {
// For COFF, the comdat group name must be the name of a symbol in the
// group. Use the counter variable name, and upgrade its linkage to
- // something externally visible, like linkonce_odr.
+ // something externally visible, like linkonce_odr. Use hidden visibility
+ // to imply that this is dso local.
CmdtPrefix = getInstrProfCountersVarPrefix();
- CounterLinkage = GlobalValue::LinkOnceODRLinkage;
+ Linkage = GlobalValue::LinkOnceODRLinkage;
+ Visibility = GlobalValue::HiddenVisibility;
}
Cmdt = M->getOrInsertComdat(getVarName(Inc, CmdtPrefix));
}
@@ -786,7 +786,7 @@
getInstrProfSectionName(IPSK_cnts, TT.getObjectFormat()));
CounterPtr->setAlignment(8);
CounterPtr->setComdat(Cmdt);
- CounterPtr->setLinkage(CounterLinkage);
+ CounterPtr->setLinkage(Linkage);
auto *Int8PtrTy = Type::getInt8PtrTy(Ctx);
// Allocate statically the array of pointers to value profile nodes for
@@ -841,6 +841,7 @@
Data->setSection(getInstrProfSectionName(IPSK_data, TT.getObjectFormat()));
Data->setAlignment(INSTR_PROF_DATA_ALIGNMENT);
Data->setComdat(Cmdt);
+ Data->setLinkage(Linkage);
PD.RegionCounters = CounterPtr;
PD.DataVar = Data;