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Dec 8, 2023
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[InstrProf][X86] Mark non-directly accessed globals as large #74778

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[InstrProf][X86] Mark non-directly accessed globals as large
aeubanks Dec 5, 2023
3a768b5
address comments
aeubanks Dec 8, 2023
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5 changes: 5 additions & 0 deletions llvm/include/llvm/Transforms/Instrumentation.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,11 @@ 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 pressure. Should typically be used for metadata globals that
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@MaskRay MaskRay Dec 8, 2023 •
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// 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 concern.

// aren't directly accessed in the module.
void setGlobalVariableLargeSection(Triple &TargetTriple, GlobalVariable &GV);

// Insert GCOV profiling instrumentation
struct GCOVOptions {
static GCOVOptions getDefault();
Expand Down
4 changes: 1 addition & 3 deletions llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
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Expand Up @@ -2146,9 +2146,7 @@ ModuleAddressSanitizer::CreateMetadataGlobal(Module &M, Constant *Initializer,
Metadata->setSection(getGlobalMetadataSection());
// Place metadata in a large section for x86-64 ELF binaries to mitigate
// relocation pressure.
if (TargetTriple.getArch() == Triple::x86_64 &&
TargetTriple.getObjectFormat() == Triple::ELF)
Metadata->setCodeModel(CodeModel::Large);
setGlobalVariableLargeSection(TargetTriple, *Metadata);
return Metadata;
}

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4 changes: 4 additions & 0 deletions llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
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Expand Up @@ -49,6 +49,7 @@
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
Expand Down Expand Up @@ -1294,6 +1295,7 @@ void InstrProfiling::createDataVariable(InstrProfCntrInstBase *Inc) {
*M, ValuesTy, false, Linkage, Constant::getNullValue(ValuesTy),
getVarName(Inc, getInstrProfValuesVarPrefix(), Renamed));
ValuesVar->setVisibility(Visibility);
setGlobalVariableLargeSection(TT, *ValuesVar);
ValuesVar->setSection(
getInstrProfSectionName(IPSK_vals, TT.getObjectFormat()));
ValuesVar->setAlignment(Align(8));
Expand Down Expand Up @@ -1422,6 +1424,7 @@ void InstrProfiling::emitVNodes() {
auto *VNodesVar = new GlobalVariable(
*M, VNodesTy, false, GlobalValue::PrivateLinkage,
Constant::getNullValue(VNodesTy), getInstrProfVNodesVarName());
setGlobalVariableLargeSection(TT, *VNodesVar);
VNodesVar->setSection(
getInstrProfSectionName(IPSK_vnodes, TT.getObjectFormat()));
VNodesVar->setAlignment(M->getDataLayout().getABITypeAlign(VNodesTy));
Expand Down Expand Up @@ -1449,6 +1452,7 @@ void InstrProfiling::emitNameData() {
GlobalValue::PrivateLinkage, NamesVal,
getInstrProfNamesVarName());
NamesSize = CompressedNameStr.size();
setGlobalVariableLargeSection(TT, *NamesVar);
NamesVar->setSection(
getInstrProfSectionName(IPSK_name, TT.getObjectFormat()));
// On COFF, it's important to reduce the alignment down to 1 to prevent the
Expand Down
7 changes: 7 additions & 0 deletions llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
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Expand Up @@ -85,3 +85,10 @@ Comdat *llvm::getOrCreateFunctionComdat(Function &F, Triple &T) {
return C;
}

void llvm::setGlobalVariableLargeSection(Triple &TargetTriple,
GlobalVariable &GV) {
if (TargetTriple.getArch() == Triple::x86_64 &&
TargetTriple.getObjectFormat() == Triple::ELF) {
GV.setCodeModel(CodeModel::Large);
}
}
23 changes: 18 additions & 5 deletions llvm/test/Instrumentation/InstrProfiling/icall-comdat.ll
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@@ -1,5 +1,4 @@
;; Check that static counters are allocated for value profiler

; RUN: opt < %s -mtriple=x86_64-unknown-linux -passes=instrprof -vp-static-alloc=true -S | FileCheck %s --check-prefix=STATIC
; RUN: opt < %s -mtriple=powerpc-unknown-linux -passes=instrprof -vp-static-alloc=true -S | FileCheck %s --check-prefix=STATIC
; RUN: opt < %s -mtriple=sparc-unknown-linux -passes=instrprof -vp-static-alloc=true -S | FileCheck %s --check-prefix=STATIC
Expand All @@ -16,6 +15,10 @@
; RUN: opt %s -mtriple=powerpc64-ibm-aix -passes=instrprof -S | FileCheck %s --check-prefix=ALIGN
; RUN: opt %s -mtriple=x86_64-unknown-linux -passes=instrprof -S | FileCheck %s --check-prefix=ALIGN

;; Check that globals have the proper code model.
; RUN: opt %s -mtriple=x86_64-unknown-linux -passes=instrprof -S | FileCheck %s --check-prefix=X8664-CODEMODEL
; RUN: opt %s -mtriple=powerpc-unknown-linux -passes=instrprof -S | FileCheck %s --check-prefix=PPC-CODEMODEL

@__profn_foo = private constant [3 x i8] c"foo"
@__profn_bar = private constant [3 x i8] c"bar"

Expand Down Expand Up @@ -46,8 +49,8 @@ declare void @llvm.instrprof.value.profile(ptr, i64, i64, i32, i32) #0

attributes #0 = { nounwind }

; STATIC: @__profvp_foo = private global [1 x i64] zeroinitializer, section "{{[^"]+}}", comdat($__profc_foo)
; STATIC: @__profvp_bar = private global [1 x i64] zeroinitializer, section "{{[^"]+}}", comdat($__profc_bar)
; STATIC: @__profvp_foo = private global [1 x i64] zeroinitializer, section "{{[^"]+}}",{{.*}} comdat($__profc_foo)
; STATIC: @__profvp_bar = private global [1 x i64] zeroinitializer, section "{{[^"]+}}",{{.*}} comdat($__profc_bar)
; STATIC: @__llvm_prf_vnodes

; DYN-NOT: @__profvp_foo
Expand All @@ -73,5 +76,15 @@ attributes #0 = { nounwind }
; ALIGN: @__profc_bar = private global {{.*}} section "__llvm_prf_cnts",{{.*}} align 8
; ALIGN: @__profvp_bar = private global {{.*}} section "__llvm_prf_vals",{{.*}} align 8
; ALIGN: @__profd_bar = private global {{.*}} section "__llvm_prf_data",{{.*}} align 8
; ALIGN: @__llvm_prf_vnodes = private global {{.*}} section "__llvm_prf_vnds", align 8
; ALIGN: @__llvm_prf_nm = private constant {{.*}} section "__llvm_prf_names", align 1
; ALIGN: @__llvm_prf_vnodes = private global {{.*}} section "__llvm_prf_vnds",{{.*}} align 8
; ALIGN: @__llvm_prf_nm = private constant {{.*}} section "__llvm_prf_names",{{.*}} align 1

; X8664-CODEMODEL-NOT: @__profc_foo = {{.*}}, code_model "large"
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; X8664-CODEMODEL:     @__profc_foo
; X8664-CODEMODEL-NOT:   code_model

ditto below to ensure that the check line finds the variables.

; X8664-CODEMODEL: @__profvp_foo = {{.*}}, code_model "large"
; X8664-CODEMODEL-NOT: @__profd_foo = {{.*}}, code_model "large"
; X8664-CODEMODEL-NOT: @__profc_bar = {{.*}}, code_model "large"
; X8664-CODEMODEL: @__profvp_bar = {{.*}}, code_model "large"
; X8664-CODEMODEL-NOT: @__profd_bar = {{.*}}, code_model "large"
; X8664-CODEMODEL: @__llvm_prf_vnodes = {{.*}}, code_model "large"
; X8664-CODEMODEL: @__llvm_prf_nm = {{.*}}, code_model "large"
; PPC-CODEMODEL-NOT: code_model "large"