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[InstrProf][X86] Set code model for counters global variables #77986

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[InstrProf][X86] Set code model for counters global variables #77986

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23 changes: 19 additions & 4 deletions llvm/include/llvm/Transforms/Instrumentation.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,10 +49,25 @@ GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
// Returns nullptr on failure.
Comdat *getOrCreateFunctionComdat(Function &F, Triple &T);

// Place global in a large section for x86-64 ELF binaries to mitigate
// relocation overflow pressure. This can be be used for metadata globals that
// aren't directly accessed by code, which has no performance impact.
void setGlobalVariableLargeSection(const Triple &TargetTriple,
// Place global in a large section for x86-64 ELF binaries in code models with
// split small/large data sections to mitigate relocation overflow pressure.
// This can be be used for metadata globals that aren't directly accessed by
// code, which has no performance impact.
void setGlobalVariableLargeCodeModel(const Triple &TargetTriple,
GlobalVariable &GV);

// Place global in a small or large section for x86-64 ELF binaries in code
// models with split small/large data sections. This can be be used for metadata
// globals that vary in size that are put into an explicit section, which can
// cause inconsistent small/large section flags on the explicit section. This
// should only be used for globals that are frequently accessed, otherwise
// setGlobalVariableLargeCodeModel() should be used to mitigate relocation
// pressure.
//
// Currently this places the variables in a small section for the medium code
// model, where performance is still a concern, but in a large section for the
// large code model, where we try to avoid all relocation pressure.
void setHotGlobalVariableCodeModel(const Triple &TargetTriple,
GlobalVariable &GV);

// Insert GCOV profiling instrumentation
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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
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Expand Up @@ -2181,7 +2181,7 @@ ModuleAddressSanitizer::CreateMetadataGlobal(Module &M, Constant *Initializer,
Metadata->setSection(getGlobalMetadataSection());
// Place metadata in a large section for x86-64 ELF binaries to mitigate
// relocation pressure.
setGlobalVariableLargeSection(TargetTriple, *Metadata);
setGlobalVariableLargeCodeModel(TargetTriple, *Metadata);
return Metadata;
}

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7 changes: 4 additions & 3 deletions llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
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Expand Up @@ -1285,6 +1285,7 @@ GlobalVariable *InstrLowerer::setupProfileSection(InstrProfInstBase *Inc,
// Put the counters and bitmaps in their own sections so linkers can
// remove unneeded sections.
Ptr->setSection(getInstrProfSectionName(IPSK, TT.getObjectFormat()));
setHotGlobalVariableCodeModel(TT, *Ptr);
Ptr->setLinkage(Linkage);
maybeSetComdat(Ptr, Fn, VarName);
return Ptr;
Expand Down Expand Up @@ -1450,7 +1451,7 @@ void InstrLowerer::createDataVariable(InstrProfCntrInstBase *Inc) {
M, ValuesTy, false, Linkage, Constant::getNullValue(ValuesTy),
getVarName(Inc, getInstrProfValuesVarPrefix(), Renamed));
ValuesVar->setVisibility(Visibility);
setGlobalVariableLargeSection(TT, *ValuesVar);
setGlobalVariableLargeCodeModel(TT, *ValuesVar);
ValuesVar->setSection(
getInstrProfSectionName(IPSK_vals, TT.getObjectFormat()));
ValuesVar->setAlignment(Align(8));
Expand Down Expand Up @@ -1588,7 +1589,7 @@ void InstrLowerer::emitVNodes() {
auto *VNodesVar = new GlobalVariable(
M, VNodesTy, false, GlobalValue::PrivateLinkage,
Constant::getNullValue(VNodesTy), getInstrProfVNodesVarName());
setGlobalVariableLargeSection(TT, *VNodesVar);
setGlobalVariableLargeCodeModel(TT, *VNodesVar);
VNodesVar->setSection(
getInstrProfSectionName(IPSK_vnodes, TT.getObjectFormat()));
VNodesVar->setAlignment(M.getDataLayout().getABITypeAlign(VNodesTy));
Expand Down Expand Up @@ -1616,7 +1617,7 @@ void InstrLowerer::emitNameData() {
GlobalValue::PrivateLinkage, NamesVal,
getInstrProfNamesVarName());
NamesSize = CompressedNameStr.size();
setGlobalVariableLargeSection(TT, *NamesVar);
setGlobalVariableLargeCodeModel(TT, *NamesVar);
NamesVar->setSection(
ProfileCorrelate == InstrProfCorrelator::BINARY
? getInstrProfSectionName(IPSK_covname, TT.getObjectFormat())
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20 changes: 18 additions & 2 deletions llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
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Expand Up @@ -85,8 +85,8 @@ Comdat *llvm::getOrCreateFunctionComdat(Function &F, Triple &T) {
return C;
}

void llvm::setGlobalVariableLargeSection(const Triple &TargetTriple,
GlobalVariable &GV) {
void llvm::setGlobalVariableLargeCodeModel(const Triple &TargetTriple,
GlobalVariable &GV) {
// Limit to x86-64 ELF.
if (TargetTriple.getArch() != Triple::x86_64 ||
TargetTriple.getObjectFormat() != Triple::ELF)
Expand All @@ -97,3 +97,19 @@ void llvm::setGlobalVariableLargeSection(const Triple &TargetTriple,
return;
GV.setCodeModel(CodeModel::Large);
}

void llvm::setHotGlobalVariableCodeModel(const Triple &TargetTriple,
GlobalVariable &GV) {
// Limit to x86-64 ELF.
if (TargetTriple.getArch() != Triple::x86_64 ||
TargetTriple.getObjectFormat() != Triple::ELF)
return;
// Limit to medium/large code models.
std::optional<CodeModel::Model> CM = GV.getParent()->getCodeModel();
if (!CM)
return;
if (*CM == CodeModel::Medium)
GV.setCodeModel(CodeModel::Small);
else if (*CM == CodeModel::Large)
GV.setCodeModel(CodeModel::Large);
}
2 changes: 1 addition & 1 deletion llvm/test/Instrumentation/InstrProfiling/section-code-model-large.ll
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Expand Up @@ -24,7 +24,7 @@ attributes #0 = { nounwind }
!0 = !{i32 1, !"Code Model", i32 4}

; CHECK: @__profc_foo =
; CHECK-NOT: code_model "large"
; CHECK-SAME: code_model "large"
; CHECK: @__profvp_foo =
; CHECK-SAME: code_model "large"
; CHECK: @__profd_foo =
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3 changes: 2 additions & 1 deletion llvm/test/Instrumentation/InstrProfiling/section-code-model-medium.ll
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Expand Up @@ -25,7 +25,8 @@ attributes #0 = { nounwind }
!0 = !{i32 1, !"Code Model", i32 3}

; CHECK: @__profc_foo =
; CHECK-NOT: code_model "large"
; X8664-SAME: code_model "small"
; PPC-NOT: code_model
; CHECK: @__profvp_foo =
; X8664-SAME: code_model "large"
; PPC-NOT: code_model "large"
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2 changes: 1 addition & 1 deletion llvm/test/Instrumentation/InstrProfiling/section-code-model-small.ll
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Expand Up @@ -24,7 +24,7 @@ attributes #0 = { nounwind }
!0 = !{i32 1, !"Code Model", i32 1}

; CHECK: @__profc_foo =
; CHECK-NOT: code_model "large"
; CHECK-NOT: code_model
; CHECK: @__profvp_foo =
; CHECK-NOT: code_model "large"
; CHECK: @__profd_foo =
Expand Down