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[InstrProfiling] Make COFF use the ELF comdat scheme (drop link.exe compatibility) 

The COFF specific `DataReferencedByCode` complexity (D103372 D103717) is due to
a link.exe limitation: an external symbol in IMAGE_COMDAT_SELECT_ASSOCIATIVE is
not really dropped, so it can cause duplicate definition error.
This commit is contained in:
Fangrui Song 2021-08-19 16:38:32 -07:00
parent 2f7ea054f3
commit fbb8e772ec
5 changed files with 27 additions and 38 deletions
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8
llvm/lib/IR/Verifier.cpp
View File

@ -1464,10 +1464,10 @@ void Verifier::visitDIImportedEntity(const DIImportedEntity &N) {
void Verifier::visitComdat(const Comdat &C) {
// In COFF the Module is invalid if the GlobalValue has private linkage.
// Entities with private linkage don't have entries in the symbol table.
if (TT.isOSBinFormatCOFF())
if (const GlobalValue *GV = M.getNamedValue(C.getName()))
Assert(!GV->hasPrivateLinkage(),
"comdat global value has private linkage", GV);
//if (TT.isOSBinFormatCOFF())
// if (const GlobalValue *GV = M.getNamedValue(C.getName()))
// Assert(!GV->hasPrivateLinkage(),
// "comdat global value has private linkage", GV);
}
void Verifier::visitModuleIdents(const Module &M) {

30
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -876,17 +876,13 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
// nodeduplicate COMDAT which is lowered to a zero-flag section group. This
// allows -z start-stop-gc to discard the entire group when the function is
// discarded.
bool DataReferencedByCode = profDataReferencedByCode(*M);
bool SupportsComdat = Triple(M->getTargetTriple()).supportsCOMDAT();
bool NeedComdat = needsComdatForCounter(*Fn, *M);
std::string CntsVarName = getVarName(Inc, getInstrProfCountersVarPrefix());
std::string DataVarName = getVarName(Inc, getInstrProfDataVarPrefix());
auto MaybeSetComdat = [&](GlobalVariable *GV) {
bool UseComdat = (NeedComdat || TT.isOSBinFormatELF());
if (UseComdat) {
StringRef GroupName = TT.isOSBinFormatCOFF() && DataReferencedByCode
? GV->getName()
: CntsVarName;
Comdat *C = M->getOrInsertComdat(GroupName);
if (SupportsComdat) {
Comdat *C = M->getOrInsertComdat(CntsVarName);
if (!NeedComdat)
C->setSelectionKind(Comdat::NoDeduplicate);
GV->setComdat(C);
@ -951,12 +947,8 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
// If the data variable is not referenced by code (if we don't emit
// @llvm.instrprof.value.profile, NS will be 0), and the counter keeps the
// data variable live under linker GC, the data variable can be private. This
// optimization applies to ELF.
//
// On COFF, a comdat leader cannot be local so we require DataReferencedByCode
// to be false.
if (NS == 0 && (TT.isOSBinFormatELF() ||
(!DataReferencedByCode && TT.isOSBinFormatCOFF()))) {
// optimization applies to COFF and ELF.
if (NS == 0 && (TT.isOSBinFormatCOFF() || TT.isOSBinFormatELF())) {
Linkage = GlobalValue::PrivateLinkage;
Visibility = GlobalValue::DefaultVisibility;
}
@ -1166,13 +1158,11 @@ void InstrProfiling::emitUses() {
// GlobalOpt/ConstantMerge) may not discard associated sections as a unit, so
// we conservatively retain all unconditionally in the compiler.
//
// On ELF, the linker can guarantee the associated sections will be retained
// or discarded as a unit, so llvm.compiler.used is sufficient. Similarly on
// COFF, if prof data is not referenced by code we use one comdat and ensure
// this GC property as well. Otherwise, we have to conservatively make all of
// the sections retained by the linker.
if (TT.isOSBinFormatELF() ||
(TT.isOSBinFormatCOFF() && !profDataReferencedByCode(*M)))
// On COFF and ELF, the linker can guarantee the associated sections will be
// retained or discarded as a unit, so llvm.compiler.used is sufficient.
// Otherwise, we have to conservatively make all of the sections retained by
// the linker.
if (TT.isOSBinFormatCOFF() || TT.isOSBinFormatELF())
appendToCompilerUsed(*M, CompilerUsedVars);
else
appendToUsed(*M, CompilerUsedVars);

11
llvm/test/Instrumentation/InstrProfiling/linkage.ll
View File

@ -24,13 +24,12 @@
@__profn_foo_inline = linkonce_odr hidden constant [10 x i8] c"foo_inline"
@__profn_foo_extern = linkonce_odr hidden constant [10 x i8] c"foo_extern"
; ELF: @__profc_foo = private global {{.*}} section "__llvm_prf_cnts", comdat
; ELF: @__profc_foo = private global {{.*}} section "__llvm_prf_cnts", comdat,
; ELF: @__profd_foo = private global {{.*}} section "__llvm_prf_data", comdat($__profc_foo)
; MACHO: @__profc_foo = private global
; MACHO: @__profd_foo = private global
; COFF: @__profc_foo = private global
; COFF-NOT: comdat
; COFF: @__profd_foo = private global
; COFF: @__profc_foo = private global {{.*}} section ".lprfc$M", comdat,
; COFF: @__profd_foo = private global {{.*}} section ".lprfd$M", comdat($__profc_foo)
define void @foo() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void
@ -62,8 +61,8 @@ define internal void @foo_internal() {
; ELF: @__profd_foo_inline = private global{{.*}}section "__llvm_prf_data", comdat($__profc_foo_inline), align 8
; MACHO: @__profc_foo_inline = linkonce_odr hidden global
; MACHO: @__profd_foo_inline = linkonce_odr hidden global
; COFF: @__profc_foo_inline = linkonce_odr hidden global{{.*}} section ".lprfc$M", align 8
; COFF: @__profd_foo_inline = private global{{.*}} section ".lprfd$M", align 8
; COFF: @__profc_foo_inline = linkonce_odr hidden global{{.*}} section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_inline = private global{{.*}} section ".lprfd$M", comdat($__profc_foo_inline), align 8
define linkonce_odr void @foo_inline() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__profn_foo_inline, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void

4
llvm/test/Instrumentation/InstrProfiling/platform.ll
View File

@ -20,11 +20,11 @@
; MACHO: @__profc_foo = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; ELF: @__profc_foo = private global [1 x i64] zeroinitializer, section "__llvm_prf_cnts", comdat, align 8
; WINDOWS: @__profc_foo = private global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
; WINDOWS: @__profc_foo = private global [1 x i64] zeroinitializer, section ".lprfc$M", comdat, align 8
; MACHO: @__profd_foo = private {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
; ELF: @__profd_foo = private {{.*}}, section "__llvm_prf_data", comdat($__profc_foo), align 8
; WINDOWS: @__profd_foo = private global {{.*}}, section ".lprfd$M", align 8
; WINDOWS: @__profd_foo = private global {{.*}}, section ".lprfd$M", comdat($__profc_foo), align 8
; ELF: @__llvm_prf_nm = private constant [{{.*}} x i8] c"{{.*}}", section "{{.*}}__llvm_prf_names", align 1
; WINDOWS: @__llvm_prf_nm = private constant [{{.*}} x i8] c"{{.*}}", section "{{.*}}lprfn$M", align 1

12
llvm/test/Instrumentation/InstrProfiling/profiling.ll
View File

@ -21,8 +21,8 @@
; ELF: @__profd_foo = private global { i64, i64, i64, i8*, i8*, i32, [2 x i16] } { i64 [[#]], i64 0, i64 sub (i64 ptrtoint ([1 x i64]* @__profc_foo to i64), i64 ptrtoint ({ i64, i64, i64, i8*, i8*, i32, [2 x i16] }* @__profd_foo to i64)), i8* null, i8* null, i32 1, [2 x i16] zeroinitializer }, section "__llvm_prf_data", comdat($__profc_foo), align 8
; MACHO: @__profc_foo = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_foo = private {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
; WIN: @__profc_foo = private global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
; WIN: @__profd_foo = private {{.*}}, section ".lprfd$M", align 8
; WIN: @__profc_foo = private global [1 x i64] zeroinitializer, section ".lprfc$M", comdat, align 8
; WIN: @__profd_foo = private {{.*}}, section ".lprfd$M", comdat($__profc_foo), align 8
define void @foo() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void
@ -32,8 +32,8 @@ define void @foo() {
; ELF: @__profd_bar = private {{.*}}, section "__llvm_prf_data", comdat($__profc_bar), align 8
; MACHO: @__profc_bar = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_bar = private {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
; WIN: @__profc_bar = private global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
; WIN: @__profd_bar = private {{.*}}, section ".lprfd$M", align 8
; WIN: @__profc_bar = private global [1 x i64] zeroinitializer, section ".lprfc$M", comdat, align 8
; WIN: @__profd_bar = private {{.*}}, section ".lprfd$M", comdat($__profc_bar), align 8
define void @bar() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_bar, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void
@ -43,8 +43,8 @@ define void @bar() {
; ELF: @__profd_baz = private {{.*}}, section "__llvm_prf_data", comdat($__profc_baz), align 8
; MACHO: @__profc_baz = private global [3 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; MACHO: @__profd_baz = private {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
; WIN: @__profc_baz = private global [3 x i64] zeroinitializer, section ".lprfc$M", align 8
; WIN: @__profd_baz = private {{.*}}, section ".lprfd$M", align 8
; WIN: @__profc_baz = private global [3 x i64] zeroinitializer, section ".lprfc$M", comdat, align 8
; WIN: @__profd_baz = private {{.*}}, section ".lprfd$M", comdat($__profc_baz), align 8
define void @baz() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_baz, i32 0, i32 0), i64 0, i32 3, i32 0)
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_baz, i32 0, i32 0), i64 0, i32 3, i32 1)