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[InstrProfiling] Use ELF section groups for counters, data and values

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__start_/__stop_ references retain C identifier name sections such as
__llvm_prf_*. Putting these into a section group disables this logic.

The ELF section group semantics ensures that group members are retained
or discarded as a unit. When a function symbol is discarded, this allows
allows linker to discard counters, data and values associated with that
function symbol as well.

Note that `noduplicates` COMDAT is lowered to zero-flag section group in
ELF. We only set this for functions that aren't already in a COMDAT and
for those that don't have available_externally linkage since we already
use regular COMDAT groups for those.

Differential Revision: https://reviews.llvm.org/D96757
This commit is contained in:
Petr Hosek 2019-07-13 14:02:07 -07:00
parent 183bbad1d7
commit 5ca21175e0
9 changed files with 141 additions and 29 deletions
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2
compiler-rt/test/CMakeLists.txt
View file

@ -22,7 +22,7 @@ if(NOT ANDROID)
# Use LLVM utils and Clang from the same build tree.
list(APPEND SANITIZER_COMMON_LIT_TEST_DEPS
clang clang-resource-headers FileCheck count not llvm-config llvm-nm llvm-objdump
llvm-readobj llvm-symbolizer compiler-rt-headers sancov)
llvm-readelf llvm-readobj llvm-symbolizer compiler-rt-headers sancov)
if (WIN32)
list(APPEND SANITIZER_COMMON_LIT_TEST_DEPS KillTheDoctor)
endif()

3
compiler-rt/test/profile/CMakeLists.txt
View file

@ -5,6 +5,9 @@ set(PROFILE_TESTSUITES)
set(PROFILE_TEST_DEPS ${SANITIZER_COMMON_LIT_TEST_DEPS})
if(NOT COMPILER_RT_STANDALONE_BUILD)
list(APPEND PROFILE_TEST_DEPS profile llvm-profdata llvm-cov)
if(NOT APPLE AND COMPILER_RT_HAS_LLD AND TARGET lld)
list(APPEND PROFILE_TEST_DEPS lld)
endif()
endif()
set(PROFILE_TEST_ARCH ${PROFILE_SUPPORTED_ARCH})

86
compiler-rt/test/profile/instrprof-gc-sections.c Normal file
View file

@ -0,0 +1,86 @@
// REQUIRES: linux, lld-available
// RUN: %clang_profgen=%t.profraw -fuse-ld=lld -fcoverage-mapping -mllvm -enable-name-compression=false -DCODE=1 -ffunction-sections -fdata-sections -Wl,--gc-sections -o %t %s
// RUN: %run %t
// RUN: llvm-profdata merge -o %t.profdata %t.profraw
// RUN: llvm-profdata show --all-functions %t.profdata | FileCheck %s -check-prefix=PROF
// RUN: llvm-cov show %t -instr-profile %t.profdata | FileCheck %s -check-prefix=COV
// RUN: llvm-nm %t | FileCheck %s -check-prefix=NM
// RUN: llvm-readelf -x __llvm_prf_names %t | FileCheck %s -check-prefix=PRF_NAMES
// RUN: llvm-readelf -x __llvm_prf_cnts %t | FileCheck %s -check-prefix=PRF_CNTS
// RUN: %clang_lto_profgen=%t.lto.profraw -fuse-ld=lld -fcoverage-mapping -mllvm -enable-name-compression=false -DCODE=1 -ffunction-sections -fdata-sections -Wl,--gc-sections -flto -o %t.lto %s
// RUN: %run %t.lto
// RUN: llvm-profdata merge -o %t.lto.profdata %t.lto.profraw
// RUN: llvm-profdata show --all-functions %t.lto.profdata | FileCheck %s -check-prefix=PROF
// RUN: llvm-cov show %t.lto -instr-profile %t.lto.profdata | FileCheck %s -check-prefix=COV
// RUN: llvm-nm %t.lto | FileCheck %s -check-prefix=NM
// RUN: llvm-readelf -x __llvm_prf_names %t.lto | FileCheck %s -check-prefix=PRF_NAMES
// RUN: llvm-readelf -x __llvm_prf_cnts %t.lto | FileCheck %s -check-prefix=PRF_CNTS
// Note: We expect foo() and some of the profiling data associated with it to
// be garbage collected.
// Note: When there is no code in a program, we expect to see the exact same
// set of external functions provided by the profile runtime.
// Note: We also check the IR instrumentation and expect foo() to be garbage
// collected as well.
// RUN: %clang_pgogen=%t.pgo.profraw -fuse-ld=lld -DCODE=1 -ffunction-sections -fdata-sections -Wl,--gc-sections -o %t.pgo %s
// RUN: %run %t.pgo
// RUN: llvm-profdata merge -o %t.pgo.profdata %t.pgo.profraw
// RUN: llvm-profdata show --all-functions %t.pgo.profdata | FileCheck %s -check-prefix=PGO
// RUN: llvm-nm %t.pgo | FileCheck %s -check-prefix=NM
#ifdef CODE
// COV: [[@LINE+1]]{{ *}}|{{ *}}0|void foo()
void foo() {}
// COV: [[@LINE+1]]{{ *}}|{{ *}}1|int main
int main() { return 0; }
#endif // CODE
// NM-NOT: foo
// PROF: Counters:
// PROF-NEXT: main:
// PROF-NEXT: Hash:
// PROF-NEXT: Counters: 1
// PROF-NEXT: Function count: 1
// PROF-NEXT: Instrumentation level: Front-end
// PROF-NEXT: Functions shown: 1
// PROF-NEXT: Total functions: 1
// PROF-NEXT: Maximum function count:
// PROF-NEXT: Maximum internal block count:
// Note: We don't expect the names of garbage collected functions to disappear
// from __llvm_prf_names, because collectPGOFuncNameStrings() glues the names
// together.
// PRF_NAMES: Hex dump of section '__llvm_prf_names':
// PRF_NAMES-NEXT: {{.*}} 0800666f 6f016d61 696e{{.*$}}
// | | f o o # m a i n
// | |___________|
// | |
// UncompressedLen = 8 |
// |
// CompressedLen = 0
// Note: We expect the profile counters for garbage collected functions to also
// be garbage collected.
// PRF_CNTS: Hex dump of section '__llvm_prf_cnts':
// PRF_CNTS-NEXT: {{.*}} 00000000 00000000 {{.*$}}
// PGO: Counters:
// PGO-NEXT: main:
// PGO-NEXT: Hash:
// PGO-NEXT: Counters: 1
// PGO-NEXT: Instrumentation level: IR
// PGO-NEXT: Functions shown: 1
// PGO-NEXT: Total functions: 1
// PGO-NEXT: Maximum function count:
// PGO-NEXT: Maximum internal block count:

15
llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
View file

@ -830,9 +830,18 @@ InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
}
std::string DataVarName = getVarName(Inc, getInstrProfDataVarPrefix());
auto MaybeSetComdat = [=](GlobalVariable *GV) {
if (NeedComdat)
GV->setComdat(M->getOrInsertComdat(TT.isOSBinFormatCOFF() ? GV->getName()
: DataVarName));
// For ELF, when not using COMDAT, put counters, data and values into
// a noduplicates COMDAT which is lowered to a zero-flag section group.
// This allows linker GC to discard the entire group when the function
// is discarded.
bool UseComdat = (NeedComdat || TT.isOSBinFormatELF());
if (UseComdat) {
auto GroupName = TT.isOSBinFormatCOFF() ? GV->getName() : DataVarName;
Comdat *C = M->getOrInsertComdat(GroupName);
if (!NeedComdat)
C->setSelectionKind(Comdat::NoDuplicates);
GV->setComdat(C);
}
};
uint64_t NumCounters = Inc->getNumCounters()->getZExtValue();

4
llvm/test/Instrumentation/InstrProfiling/icall.ll
View file

@ -43,8 +43,8 @@ declare void @llvm.instrprof.value.profile(i8*, i64, i64, i32, i32) #0
attributes #0 = { nounwind }
; STATIC: @__profvp_foo = private global [1 x i64] zeroinitializer, section "{{[^"]+}}", align 8
; STATIC: @__profvp_bar = private global [1 x i64] zeroinitializer, section "{{[^"]+}}", comdat($__profd_bar), align 8
; STATIC: @__profvp_foo = private global [1 x i64] zeroinitializer, section "{{[^"]+}}"
; STATIC: @__profvp_bar = private global [1 x i64] zeroinitializer, section "{{[^"]+}}", comdat($__profd_bar)
; STATIC: @__llvm_prf_vnodes
; DYN-NOT: @__profvp_foo

52
llvm/test/Instrumentation/InstrProfiling/linkage.ll
View file

@ -1,16 +1,22 @@
;; Check that runtime symbols get appropriate linkage.
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s --check-prefixes=POSIX,MACHO
; RUN: opt < %s -mtriple=x86_64-unknown-linux -instrprof -S | FileCheck %s --check-prefixes=POSIX,LINUX
; RUN: opt < %s -mtriple=x86_64-unknown-fuchsia -instrprof -S | FileCheck %s --check-prefixes=POSIX,LINUX
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -instrprof -S | FileCheck %s --check-prefixes=MACHO
; RUN: opt < %s -mtriple=x86_64-unknown-linux -instrprof -S | FileCheck %s --check-prefixes=ELF
; RUN: opt < %s -mtriple=x86_64-unknown-fuchsia -instrprof -S | FileCheck %s --check-prefixes=ELF
; RUN: opt < %s -mtriple=x86_64-pc-win32-coff -instrprof -S | FileCheck %s --check-prefixes=COFF
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -passes=instrprof -S | FileCheck %s --check-prefixes=POSIX,MACHO
; RUN: opt < %s -mtriple=x86_64-unknown-linux -passes=instrprof -S | FileCheck %s --check-prefixes=POSIX,LINUX
; RUN: opt < %s -mtriple=x86_64-unknown-fuchsia -passes=instrprof -S | FileCheck %s --check-prefixes=POSIX,LINUX
; RUN: opt < %s -mtriple=x86_64-apple-macosx10.10.0 -passes=instrprof -S | FileCheck %s --check-prefixes=MACHO
; RUN: opt < %s -mtriple=x86_64-unknown-linux -passes=instrprof -S | FileCheck %s --check-prefixes=ELF
; RUN: opt < %s -mtriple=x86_64-unknown-fuchsia -passes=instrprof -S | FileCheck %s --check-prefixes=ELF
; RUN: opt < %s -mtriple=x86_64-pc-win32-coff -passes=instrprof -S | FileCheck %s --check-prefixes=COFF
; MACHO: @__llvm_profile_runtime = external global i32
; LINUX-NOT: @__llvm_profile_runtime = external global i32
; ELF-NOT: @__llvm_profile_runtime = external global i32
; ELF: $__profd_foo = comdat noduplicates
; ELF: $__profd_foo_weak = comdat noduplicates
; ELF: $"__profd_linkage.ll:foo_internal" = comdat noduplicates
; ELF: $__profd_foo_inline = comdat noduplicates
; ELF: $__profd_foo_extern = comdat any
@__profn_foo = hidden constant [3 x i8] c"foo"
@__profn_foo_weak = weak hidden constant [8 x i8] c"foo_weak"
@ -18,8 +24,10 @@
@__profn_foo_inline = linkonce_odr hidden constant [10 x i8] c"foo_inline"
@__profn_foo_extern = linkonce_odr hidden constant [10 x i8] c"foo_extern"
; POSIX: @__profc_foo = hidden global
; POSIX: @__profd_foo = hidden global
; ELF: @__profc_foo = hidden global{{.*}}section "__llvm_prf_cnts", comdat($__profd_foo)
; ELF: @__profd_foo = hidden global{{.*}}section "__llvm_prf_data", comdat
; MACHO: @__profc_foo = hidden global
; MACHO: @__profd_foo = hidden global
; COFF: @__profc_foo = internal global
; COFF-NOT: comdat
; COFF: @__profd_foo = internal global
@ -28,8 +36,10 @@ define void @foo() {
ret void
}
; POSIX: @__profc_foo_weak = weak hidden global
; POSIX: @__profd_foo_weak = weak hidden global
; ELF: @__profc_foo_weak = weak hidden global{{.*}}section "__llvm_prf_cnts", comdat($__profd_foo_weak)
; ELF: @__profd_foo_weak = weak hidden global{{.*}}section "__llvm_prf_data", comdat
; MACHO: @__profc_foo_weak = weak hidden global
; MACHO: @__profd_foo_weak = weak hidden global
; COFF: @__profc_foo_weak = internal global
; COFF: @__profd_foo_weak = internal global
define weak void @foo_weak() {
@ -37,8 +47,10 @@ define weak void @foo_weak() {
ret void
}
; POSIX: @"__profc_linkage.ll:foo_internal" = internal global
; POSIX: @"__profd_linkage.ll:foo_internal" = internal global
; ELF: @"__profc_linkage.ll:foo_internal" = internal global{{.*}}section "__llvm_prf_cnts", comdat($"__profd_linkage.ll:foo_internal")
; ELF: @"__profd_linkage.ll:foo_internal" = internal global{{.*}}section "__llvm_prf_data", comdat
; MACHO: @"__profc_linkage.ll:foo_internal" = internal global
; MACHO: @"__profd_linkage.ll:foo_internal" = internal global
; COFF: @"__profc_linkage.ll:foo_internal" = internal global
; COFF: @"__profd_linkage.ll:foo_internal" = internal global
define internal void @foo_internal() {
@ -46,8 +58,10 @@ define internal void @foo_internal() {
ret void
}
; POSIX: @__profc_foo_inline = linkonce_odr hidden global
; POSIX: @__profd_foo_inline = linkonce_odr hidden global
; ELF: @__profc_foo_inline = linkonce_odr hidden global{{.*}}section "__llvm_prf_cnts", comdat($__profd_foo_inline)
; ELF: @__profd_foo_inline = linkonce_odr hidden global{{.*}}section "__llvm_prf_data", comdat
; MACHO: @__profc_foo_inline = linkonce_odr hidden global
; MACHO: @__profd_foo_inline = linkonce_odr hidden global
; COFF: @__profc_foo_inline = internal global{{.*}} section ".lprfc$M", align 8
; COFF: @__profd_foo_inline = internal global{{.*}} section ".lprfd$M", align 8
define linkonce_odr void @foo_inline() {
@ -55,8 +69,8 @@ define linkonce_odr void @foo_inline() {
ret void
}
; LINUX: @__profc_foo_extern = linkonce_odr hidden global {{.*}}section "__llvm_prf_cnts", comdat($__profd_foo_extern), align 8
; LINUX: @__profd_foo_extern = linkonce_odr hidden global {{.*}}section "__llvm_prf_data", comdat, align 8
; ELF: @__profc_foo_extern = linkonce_odr hidden global {{.*}}section "__llvm_prf_cnts", comdat($__profd_foo_extern), align 8
; ELF: @__profd_foo_extern = linkonce_odr hidden global {{.*}}section "__llvm_prf_data", comdat, align 8
; MACHO: @__profc_foo_extern = linkonce_odr hidden global
; MACHO: @__profd_foo_extern = linkonce_odr hidden global
; COFF: @__profc_foo_extern = linkonce_odr hidden global {{.*}}section ".lprfc$M", comdat, align 8
@ -73,5 +87,5 @@ declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
; MACHO: ret i32 %[[REG]]
; MACHO: }
; COFF: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} comdat {
; LINUX-NOT: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
; LINUX-NOT: %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime
; ELF-NOT: define linkonce_odr hidden i32 @__llvm_profile_runtime_user() {{.*}} {
; ELF-NOT: %[[REG:.*]] = load i32, i32* @__llvm_profile_runtime

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

@ -19,11 +19,11 @@
; WINDOWS-NOT: __profn_foo
; MACHO: @__profc_foo = hidden global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
; ELF: @__profc_foo = hidden global [1 x i64] zeroinitializer, section "__llvm_prf_cnts", align 8
; ELF: @__profc_foo = hidden global [1 x i64] zeroinitializer, section "__llvm_prf_cnts", comdat($__profd_foo), align 8
; WINDOWS: @__profc_foo = internal global [1 x i64] zeroinitializer, section ".lprfc$M", align 8
; MACHO: @__profd_foo = hidden {{.*}}, section "__DATA,__llvm_prf_data,regular,live_support", align 8
; ELF: @__profd_foo = hidden {{.*}}, section "__llvm_prf_data", align 8
; ELF: @__profd_foo = hidden {{.*}}, section "__llvm_prf_data", comdat, align 8
; WINDOWS: @__profd_foo = internal global {{.*}}, section ".lprfd$M", align 8
; ELF: @__llvm_prf_nm = private constant [{{.*}} x i8] c"{{.*}}", section "{{.*}}__llvm_prf_names", align 1

2
llvm/test/Transforms/PGOProfile/counter_promo.ll
View file

@ -60,7 +60,7 @@ bb12: ; preds = %bb9
; ATOMIC_PROMO: atomicrmw add {{.*}} @__profc_foo{{.*}}0), i64 %[[LIVEOUT1]] seq_cst
; ATOMIC_PROMO-NEXT: atomicrmw add {{.*}} @__profc_foo{{.*}}1), i64 %[[LIVEOUT2]] seq_cst
; ATOMIC_PROMO-NEXT: atomicrmw add {{.*}} @__profc_foo{{.*}}2), i64 %[[LIVEOUT3]] seq_cst
; PROMO-NOT: @__profc_foo
; PROMO-NOT: @__profc_foo{{.*}})
}

2
llvm/test/Transforms/PGOProfile/counter_promo_mexits.ll
View file

@ -69,7 +69,7 @@ bb15_0: ; preds = %bb11
; PROMO-NEXT: %pgocount{{.*}} = load {{.*}} @__profc_foo{{.*}} 4)
; PROMO-NEXT: add
; PROMO-NEXT: store {{.*}}@__profc_foo{{.*}}4)
; PROMO-NOT: @__profc_foo
; PROMO-NOT: @__profc_foo{{.*}})
bb15: ; preds = %bb14, %bb4