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[LTO] Make local linkage GlobalValue in non-prevailing COMDAT availab…
…le_externally For a local linkage GlobalObject in a non-prevailing COMDAT, it remains defined while its leader has been made available_externally. This violates the COMDAT rule that its members must be retained or discarded as a unit. To fix this, update the regular LTO change D34803 to track local linkage GlobalValues, and port the code to ThinLTO (GlobalAliases are not handled.) This fixes two problems. (a) `__cxx_global_var_init` in a non-prevailing COMDAT group used to linger around (unreferenced, hence benign), and is now correctly discarded. ``` int foo(); inline int v = foo(); ``` (b) Fix #58215: as a size optimization, we place private `__profd_` in a COMDAT with a `__profc_` key. When FuncImport.cpp makes `__profc_` available_externally due to a non-prevailing COMDAT, `__profd_` incorrectly remains private. This change makes the `__profd_` available_externally. ``` cat > c.h <<'eof' extern void bar(); inline __attribute__((noinline)) void foo() {} eof cat > m1.cc <<'eof' #include "c.h" int main() { bar(); foo(); } eof cat > m2.cc <<'eof' #include "c.h" __attribute__((noinline)) void bar() { foo(); } eof clang -O2 -fprofile-generate=./t m1.cc m2.cc -flto -fuse-ld=lld -o t_gen rm -fr t && ./t_gen && llvm-profdata show -function=foo t/default_*.profraw clang -O2 -fprofile-generate=./t m1.cc m2.cc -flto=thin -fuse-ld=lld -o t_gen rm -fr t && ./t_gen && llvm-profdata show -function=foo t/default_*.profraw ``` If a GlobalAlias references a GlobalValue which is just changed to available_externally, change the GlobalAlias as well (e.g. C5/D5 comdats due to cc1 -mconstructor-aliases). The GlobalAlias may be referenced by other available_externally functions, so it cannot easily be removed. Depends on D137441: we use available_externally to mark a GlobalAlias in a non-prevailing COMDAT, similar to how we handle GlobalVariable/Function. GlobalAlias may refer to a ConstantExpr, not changing GlobalAlias to GlobalVariable gives flexibility for future extensions (the use case is niche. For simplicity we don't handle it yet). In addition, available_externally GlobalAlias is the most straightforward implementation and retains the aliasee information to help optimizers. See windows-vftable.ll: Windows vftable uses an alias pointing to a private constant where the alias is the COMDAT leader. The COMDAT use case is skeptical and ThinLTO does not discard the alias in the non-prevailing COMDAT. This patch retains the behavior. Reviewed By: tejohnson Differential Revision: https://reviews.llvm.org/D135427
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17 changes: 14 additions & 3 deletions
17
llvm/test/ThinLTO/X86/Inputs/linkonce_resolution_comdat.ll
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@@ -1,13 +1,24 @@ | ||
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" | ||
target triple = "x86_64-unknown-linux-gnu" | ||
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$c2 = comdat any | ||
$f = comdat any | ||
$g = comdat any | ||
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define linkonce_odr i32 @f(i8*) unnamed_addr comdat($c2) { | ||
@g_private = private global i32 41, comdat($g) | ||
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define linkonce_odr i32 @f(i8*) unnamed_addr comdat($f) { | ||
ret i32 41 | ||
} | ||
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define linkonce_odr i32 @g() unnamed_addr comdat($g) { | ||
ret i32 41 | ||
} | ||
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define i32 @g() { | ||
define internal void @g_internal() unnamed_addr comdat($g) { | ||
ret void | ||
} | ||
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define i32 @h() { | ||
%i = call i32 @f(i8* null) | ||
ret i32 %i | ||
} |
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@@ -0,0 +1,44 @@ | ||
;; The constructor alias example is reduced from | ||
;; | ||
;; template <typename T> | ||
;; struct A { A() {} virtual ~A() {} }; | ||
;; template struct A<void>; | ||
;; void *foo() { return new A<void>; } | ||
;; | ||
;; clang -c -fpic -O1 -flto=thin a.cc && cp a.o b.o && ld.lld -shared a.o b.so | ||
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; RUN: opt -module-summary %s -o %t1.bc | ||
; RUN: cp %t1.bc %t2.bc | ||
; RUN: llvm-lto2 run %t1.bc %t2.bc -r=%t1.bc,_ZTV1A,pl -r=%t1.bc,_ZN1AD0Ev,pl -r=%t1.bc,_ZN1AD1Ev,pl -r=%t1.bc,_ZN1AD2Ev,pl -r=%t1.bc,D1_a,pl -r=%t1.bc,D1_a_a,pl \ | ||
; RUN: -r=%t2.bc,_ZTV1A,l -r=%t2.bc,_ZN1AD0Ev,l -r=%t2.bc,_ZN1AD1Ev,l -r=%t2.bc,_ZN1AD2Ev,l -r=%t2.bc,D1_a,l -r=%t2.bc,D1_a_a,l -o %t3 --save-temps | ||
; RUN: llvm-dis < %t3.2.1.promote.bc | FileCheck %s | ||
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; CHECK: @_ZTV1A = available_externally dso_local unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr null, ptr @_ZN1AD1Ev, ptr @_ZN1AD0Ev] } | ||
; CHECK: @D1_a = available_externally dso_local unnamed_addr alias void (ptr), ptr @_ZN1AD1Ev | ||
; CHECK: @_ZN1AD1Ev = available_externally dso_local unnamed_addr alias void (ptr), ptr @_ZN1AD2Ev | ||
; CHECK: @D1_a_a = available_externally dso_local unnamed_addr alias void (ptr), ptr @D1_a | ||
; CHECK: define available_externally dso_local void @_ZN1AD2Ev(ptr noundef nonnull %0) unnamed_addr { | ||
; CHECK: define available_externally dso_local void @_ZN1AD0Ev(ptr noundef nonnull %0) unnamed_addr { | ||
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" | ||
target triple = "x86_64-unknown-linux-gnu" | ||
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$_ZN1AD5Ev = comdat any | ||
$_ZTV1A = comdat any | ||
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@_ZTV1A = weak_odr unnamed_addr constant { [4 x ptr] } { [4 x ptr] [ptr null, ptr null, ptr @_ZN1AD1Ev, ptr @_ZN1AD0Ev] }, comdat | ||
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@D1_a = weak_odr unnamed_addr alias void (ptr), ptr @_ZN1AD1Ev | ||
@_ZN1AD1Ev = weak_odr unnamed_addr alias void (ptr), ptr @_ZN1AD2Ev | ||
@D1_a_a = weak_odr unnamed_addr alias void (ptr), ptr @D1_a | ||
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define weak_odr void @_ZN1AD2Ev(ptr noundef nonnull %0) unnamed_addr comdat($_ZN1AD5Ev) { | ||
ret void | ||
} | ||
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define weak_odr void @_ZN1AD0Ev(ptr noundef nonnull %0) unnamed_addr comdat($_ZN1AD5Ev) { | ||
call void @D1_a(ptr noundef nonnull %0) | ||
call void @D1_a_a(ptr noundef nonnull %0) | ||
call void @_ZN1AD1Ev(ptr noundef nonnull %0) | ||
ret void | ||
} |
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; This test ensures that we drop the preempted copy of @f from %t2.bc from its | ||
; comdat after making it available_externally. If not we would get a | ||
; verification error. | ||
; This test ensures that we drop the preempted copy of @f/@g from %t2.bc from their | ||
; comdats after making it available_externally. If not we would get a | ||
; verification error. g_internal/g_private are changed to available_externally | ||
; as well since it is in the same comdat of g. | ||
; RUN: opt -module-summary %s -o %t1.bc | ||
; RUN: opt -module-summary %p/Inputs/linkonce_resolution_comdat.ll -o %t2.bc | ||
; RUN: llvm-lto -thinlto-action=run -disable-thinlto-funcattrs=0 %t1.bc %t2.bc -exported-symbol=f -exported-symbol=g -thinlto-save-temps=%t3. | ||
; RUN: llvm-lto -thinlto-action=run -disable-thinlto-funcattrs=0 %t1.bc %t2.bc -exported-symbol=f -exported-symbol=g -exported-symbol=h -thinlto-save-temps=%t3. | ||
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; RUN: llvm-dis %t3.0.3.imported.bc -o - | FileCheck %s --check-prefix=IMPORT1 | ||
; RUN: llvm-dis %t3.1.3.imported.bc -o - | FileCheck %s --check-prefix=IMPORT2 | ||
; Copy from first module is prevailing and converted to weak_odr, copy | ||
; from second module is preempted and converted to available_externally and | ||
; removed from comdat. | ||
; IMPORT1: define weak_odr i32 @f(i8* %0) unnamed_addr [[ATTR:#[0-9]+]] comdat($c1) { | ||
; IMPORT1: @g_private = private global i32 43, comdat($g) | ||
; IMPORT1: define weak_odr i32 @f(i8* %0) unnamed_addr [[ATTR:#[0-9]+]] comdat { | ||
; IMPORT1: define weak_odr i32 @g() unnamed_addr [[ATTR]] comdat { | ||
; IMPORT1: define internal void @g_internal() unnamed_addr comdat($g) { | ||
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; IMPORT2: @g_private = available_externally dso_local global i32 41{{$}} | ||
; IMPORT2: define available_externally i32 @f(i8* %0) unnamed_addr [[ATTR:#[0-9]+]] { | ||
; IMPORT2: define available_externally i32 @g() unnamed_addr [[ATTR]] { | ||
; IMPORT2: define available_externally dso_local void @g_internal() unnamed_addr { | ||
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; CHECK-DAG: attributes [[ATTR]] = { norecurse nounwind } | ||
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; RUN: llvm-nm -o - < %t1.bc.thinlto.o | FileCheck %s --check-prefix=NM1 | ||
; RUN: llvm-nm %t1.bc.thinlto.o | FileCheck %s --check-prefix=NM1 | ||
; NM1: W f | ||
; NM1: W g | ||
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; RUN: llvm-nm -o - < %t2.bc.thinlto.o | FileCheck %s --check-prefix=NM2 | ||
; RUN: llvm-nm %t2.bc.thinlto.o | FileCheck %s --check-prefix=NM2 | ||
; f() would have been turned into available_externally since it is preempted, | ||
; and inlined into g() | ||
; and inlined into h() | ||
; NM2-NOT: f | ||
; NM2-NOT: g | ||
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" | ||
target triple = "x86_64-unknown-linux-gnu" | ||
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$c1 = comdat any | ||
$f = comdat any | ||
$g = comdat any | ||
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@g_private = private global i32 43, comdat($g) | ||
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define linkonce_odr i32 @f(i8*) unnamed_addr comdat($c1) { | ||
define linkonce_odr i32 @f(i8*) unnamed_addr comdat { | ||
ret i32 43 | ||
} | ||
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define linkonce_odr i32 @g() unnamed_addr comdat { | ||
ret i32 43 | ||
} | ||
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define internal void @g_internal() unnamed_addr comdat($g) { | ||
ret void | ||
} |
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@@ -0,0 +1,35 @@ | ||
;; Test an alias pointing to a GEP. | ||
; RUN: opt -module-summary %s -o %t1.bc | ||
; RUN: cp %t1.bc %t2.bc | ||
; RUN: llvm-lto2 run %t1.bc %t2.bc -r=%t1.bc,"??_7bad_array_new_length@stdext@@6B@",pl -r=%t1.bc,"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z",pl \ | ||
; RUN: -r=%t1.bc,"?_Throw_bad_array_new_length@std@@YAXXZ",pl \ | ||
; RUN: -r=%t2.bc,"??_7bad_array_new_length@stdext@@6B@", -r=%t2.bc,"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z", \ | ||
; RUN: -r=%t2.bc,"?_Throw_bad_array_new_length@std@@YAXXZ", -o %t3 --save-temps | ||
; RUN: llvm-dis < %t3.2.1.promote.bc | FileCheck %s | ||
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; CHECK: @anon = private unnamed_addr constant { [2 x ptr] } { [2 x ptr] [ptr null, ptr @"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z"] }, comdat($"??_7bad_array_new_length@stdext@@6B@") | ||
; CHECK: @"??_7bad_array_new_length@stdext@@6B@" = unnamed_addr alias ptr, getelementptr inbounds ({ [4 x ptr] }, ptr @anon, i32 0, i32 0, i32 1){{$}} | ||
; CHECK: define available_externally dso_local noundef ptr @"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z"(ptr noundef nonnull %this) { | ||
; CHECK: define available_externally dso_local void @"?_Throw_bad_array_new_length@std@@YAXXZ"(ptr noundef nonnull %0) unnamed_addr { | ||
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target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128" | ||
target triple = "x86_64-pc-windows-msvc19.26.0" | ||
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$"??_7bad_array_new_length@stdext@@6B@" = comdat largest | ||
$"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z" = comdat any | ||
$"?_Throw_bad_array_new_length@std@@YAXXZ" = comdat any | ||
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@anon = private unnamed_addr constant { [2 x ptr] } { [2 x ptr] [ptr null, ptr @"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z"] }, comdat($"??_7bad_array_new_length@stdext@@6B@") | ||
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@"??_7bad_array_new_length@stdext@@6B@" = unnamed_addr alias ptr, getelementptr inbounds ({ [4 x ptr] }, ptr @anon, i32 0, i32 0, i32 1) | ||
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define linkonce_odr dso_local noundef ptr @"??_Gbad_array_new_length@stdext@@UEAAPEAXI@Z"(ptr noundef nonnull %this) comdat { | ||
entry: | ||
ret ptr %this | ||
} | ||
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define linkonce_odr dso_local void @"?_Throw_bad_array_new_length@std@@YAXXZ"(ptr noundef nonnull %0) unnamed_addr comdat { | ||
entry: | ||
store ptr @"??_7bad_array_new_length@stdext@@6B@", ptr %0, align 8 | ||
ret void | ||
} |