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[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
This commit is contained in:
Reid Kleckner 2019-09-16 18:49:09 +00:00
parent 69911b8d01
commit 32837a0c93
4 changed files with 16 additions and 15 deletions
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15
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
View File

@ -740,9 +740,8 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
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 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
// 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 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
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 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
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;

4
llvm/test/Instrumentation/InstrProfiling/PR23499.ll
View File

@ -20,8 +20,8 @@ $_Z3barIvEvv = comdat any
; COFF-NOT: __profn__Z3barIvEvv
; COFF: @__profc__Z3barIvEvv = linkonce_odr dso_local global [1 x i64] zeroinitializer, section "{{.*}}prfc$M", comdat, align 8
; COFF: @__profd__Z3barIvEvv = internal global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [2 x i16] zeroinitializer }, section "{{.*}}prfd{{.*}}", comdat($__profc__Z3barIvEvv), align 8
; COFF: @__profc__Z3barIvEvv = linkonce_odr hidden global [1 x i64] zeroinitializer, section "{{.*}}prfc$M", comdat, align 8
; COFF: @__profd__Z3barIvEvv = linkonce_odr hidden global { i64, i64, i64*, i8*, i8*, i32, [2 x i16] } { i64 4947693190065689389, i64 0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc__Z3barIvEvv, i32 0, i32 0), i8*{{.*}}, i8* null, i32 1, [2 x i16] zeroinitializer }, section "{{.*}}prfd{{.*}}", comdat($__profc__Z3barIvEvv), align 8
declare void @llvm.instrprof.increment(i8*, i64, i32, i32) #1

8
llvm/test/Instrumentation/InstrProfiling/comdat.ll
View File

@ -17,8 +17,8 @@ $foo_inline = comdat any
; ELF: @__profc_foo_inline = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat($__profv_foo_inline), align 8
; ELF: @__profd_foo_inline = linkonce_odr hidden global{{.*}}, section "__llvm_prf_data", comdat($__profv_foo_inline), align 8
; COFF: @__profc_foo_inline = linkonce_odr dso_local global{{.*}}, section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_inline = internal global{{.*}}, section ".lprfd$M", comdat($__profc_foo_inline), align 8
; COFF: @__profc_foo_inline = linkonce_odr hidden global{{.*}}, section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_inline = linkonce_odr hidden global{{.*}}, section ".lprfd$M", comdat($__profc_foo_inline), align 8
define weak_odr void @foo_inline() comdat {
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
@ -30,8 +30,8 @@ $foo_extern = comdat any
; ELF: @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section "__llvm_prf_cnts", comdat($__profv_foo_extern)
; ELF: @__profd_foo_extern = linkonce_odr hidden global{{.*}}, section "__llvm_prf_data", comdat($__profv_foo_extern)
; COFF: @__profc_foo_extern = linkonce_odr dso_local global{{.*}}, section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_extern = internal global{{.*}}, section ".lprfd$M", comdat($__profc_foo_extern), align 8
; COFF: @__profc_foo_extern = linkonce_odr hidden global{{.*}}, section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_extern = linkonce_odr hidden global{{.*}}, section ".lprfd$M", comdat($__profc_foo_extern), align 8
define available_externally void @foo_extern() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__profn_foo_extern, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void

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

@ -57,8 +57,8 @@ define linkonce_odr void @foo_inline() {
; LINUX: @__profd_foo_extern = linkonce_odr hidden global {{.*}}section "__llvm_prf_data", comdat($__profv_foo_extern), align 8
; MACHO: @__profc_foo_extern = linkonce_odr hidden global
; MACHO: @__profd_foo_extern = linkonce_odr hidden global
; COFF: @__profc_foo_extern = linkonce_odr dso_local global {{.*}}section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_extern = internal global {{.*}}section ".lprfd$M", comdat($__profc_foo_extern), align 8
; COFF: @__profc_foo_extern = linkonce_odr hidden global {{.*}}section ".lprfc$M", comdat, align 8
; COFF: @__profd_foo_extern = linkonce_odr hidden global {{.*}}section ".lprfd$M", comdat($__profc_foo_extern), align 8
define available_externally void @foo_extern() {
call void @llvm.instrprof.increment(i8* getelementptr inbounds ([10 x i8], [10 x i8]* @__profn_foo_extern, i32 0, i32 0), i64 0, i32 1, i32 0)
ret void