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llvm-project/lld/test/ELF/lto/devirt_split_unit_localize.ll

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[lld:elf] Weaken the requirement for a computed binding to be STB_LOCAL Given the following scenario: ``` // Cat.cpp struct Animal { virtual void makeNoise() const = 0; }; struct Cat : Animal { void makeNoise() const override; }; extern "C" int puts(char const *); void Cat::makeNoise() const { puts("Meow"); } void doThingWithCat(Animal *a) { static_cast<Cat *>(a)->makeNoise(); } // CatUser.cpp struct Animal { virtual void makeNoise() const = 0; }; struct Cat : Animal { void makeNoise() const override; }; void doThingWithCat(Animal *a); void useDoThingWithCat() { Cat *d = new Cat; doThingWithCat(d); } // cat.ver { global: _Z17useDoThingWithCatv; local: *; }; $ clang++ Cat.cpp CatUser.cpp -fpic -flto=thin -fwhole-program-vtables -shared -O3 -fuse-ld=lld -Wl,--lto-whole-program-visibility -Wl,--version-script,cat.ver ``` We cannot devirtualize `Cat::makeNoise`. The issue is complex: Due to `-fsplit-lto-unit` and usage of type metadata, we place the Cat vtable declaration into module 0 and the Cat vtable definition with type metadata into module 1, causing duplicate entries (Undefined followed by Defined) in the `lto::InputFile::symbols()` output. In `BitcodeFile::parse`, after processing the `Undefined` then the `Defined`, the final state is `Defined`. In `BitcodeCompiler::add`, for the first symbol, `computeBinding` returns `STB_LOCAL`, then we reset it to `Undefined` because it is prevailing (`versionId` is `preserved`). For the second symbol, because the state is now `Undefined`, `computeBinding` returns `STB_GLOBAL`, causing `ExportDynamic` to be true and suppressing devirtualization. In D77280, the `computeBinding` change used a stricter `isDefined()` condition to make weak``Lazy` symbol work. This patch relaxes the condition to weaker `!isLazy()` to keep it working while making the devirtualization work as well. Differential Revision: https://reviews.llvm.org/D98686
2021-03-16 16:33:50 +08:00
; REQUIRES: x86
;; Test that that a vtable defined locally in one module but external in another
;; does not prevent devirtualization.
;; Hybrid WPD
; RUN: split-file %s %t
; RUN: opt --thinlto-bc --thinlto-split-lto-unit -o %t/Cat.o %t/Cat.ll
; RUN: opt --thinlto-bc --thinlto-split-lto-unit -o %t/User.o %t/User.ll
; RUN: echo '{ global: _Z17useDoThingWithCatv; local: *; };' > %t/version.exp
; RUN: ld.lld %t/Cat.o %t/User.o -shared -o %t/libA.so -save-temps --lto-whole-program-visibility \
; RUN: -mllvm -pass-remarks=. --version-script %t/version.exp 2>&1 | \
; RUN: FileCheck %s --check-prefix=REMARK
; REMARK-DAG: <unknown>:0:0: single-impl: devirtualized a call to _ZNK3Cat9makeNoiseEv
; REMARK-DAG: <unknown>:0:0: single-impl: devirtualized a call to _ZNK3Cat9makeNoiseEv
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"
;--- Cat.ll
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"
%struct.Cat = type { %struct.Animal }
%struct.Animal = type { i32 (...)** }
$_ZTS6Animal = comdat any
$_ZTI6Animal = comdat any
@.str = private unnamed_addr constant [5 x i8] c"Meow\00", align 1
@_ZTV3Cat = dso_local unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI3Cat to i8*), i8* bitcast (void (%struct.Cat*)* @_ZNK3Cat9makeNoiseEv to i8*)] }, align 8, !type !0, !type !1, !type !2, !type !3
@_ZTVN10__cxxabiv120__si_class_type_infoE = external dso_local global i8*
@_ZTS3Cat = dso_local constant [5 x i8] c"3Cat\00", align 1
@_ZTVN10__cxxabiv117__class_type_infoE = external dso_local global i8*
@_ZTS6Animal = linkonce_odr dso_local constant [8 x i8] c"6Animal\00", comdat, align 1
@_ZTI6Animal = linkonce_odr dso_local constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([8 x i8], [8 x i8]* @_ZTS6Animal, i32 0, i32 0) }, comdat, align 8
@_ZTI3Cat = dso_local constant { i8*, i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv120__si_class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([5 x i8], [5 x i8]* @_ZTS3Cat, i32 0, i32 0), i8* bitcast ({ i8*, i8* }* @_ZTI6Animal to i8*) }, align 8
define dso_local void @_ZNK3Cat9makeNoiseEv(%struct.Cat* nocapture nonnull readnone dereferenceable(8) %this) unnamed_addr align 2 {
entry:
%call = tail call i32 @puts(i8* nonnull dereferenceable(1) getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0))
ret void
}
declare dso_local noundef i32 @puts(i8* nocapture noundef readonly) local_unnamed_addr
define dso_local void @_Z14doThingWithCatP6Animal(%struct.Animal* %a) local_unnamed_addr {
entry:
%tobool.not = icmp eq %struct.Animal* %a, null
br i1 %tobool.not, label %if.end, label %if.then
if.then: ; preds = %entry
%0 = bitcast %struct.Animal* %a to %struct.Cat*
%1 = bitcast %struct.Animal* %a to void (%struct.Cat*)***
%vtable = load void (%struct.Cat*)**, void (%struct.Cat*)*** %1, align 8, !tbaa !4
%2 = bitcast void (%struct.Cat*)** %vtable to i8*
%3 = tail call i1 @llvm.type.test(i8* %2, metadata !"_ZTS3Cat")
tail call void @llvm.assume(i1 %3)
%4 = load void (%struct.Cat*)*, void (%struct.Cat*)** %vtable, align 8
tail call void %4(%struct.Cat* nonnull dereferenceable(8) %0)
br label %if.end
if.end: ; preds = %if.then, %entry
ret void
}
declare i1 @llvm.type.test(i8*, metadata)
declare void @llvm.assume(i1 noundef)
!0 = !{i64 16, !"_ZTS3Cat"}
!1 = !{i64 16, !"_ZTSM3CatKFvvE.virtual"}
!2 = !{i64 16, !"_ZTS6Animal"}
!3 = !{i64 16, !"_ZTSM6AnimalKFvvE.virtual"}
!4 = !{!5, !5, i64 0}
!5 = !{!"vtable pointer", !6, i64 0}
!6 = !{!"Simple C++ TBAA"}
;--- User.ll
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"
%struct.Animal = type { i32 (...)** }
%struct.Cat = type { %struct.Animal }
@_ZTV3Cat = available_externally dso_local unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast (i8** @_ZTI3Cat to i8*), i8* bitcast (void (%struct.Cat*)* @_ZNK3Cat9makeNoiseEv to i8*)] }, align 8, !type !0, !type !1, !type !2, !type !3
@_ZTI3Cat = external dso_local constant i8*
@llvm.compiler.used = appending global [1 x i8*] [i8* bitcast ({ [3 x i8*] }* @_ZTV3Cat to i8*)], section "llvm.metadata"
declare dso_local void @_ZNK3Cat9makeNoiseEv(%struct.Cat* nonnull dereferenceable(8)) unnamed_addr
define dso_local void @_Z17useDoThingWithCatv() local_unnamed_addr {
entry:
%call = tail call noalias nonnull dereferenceable(8) i8* @_Znwm(i64 8)
%0 = bitcast i8* %call to i32 (...)***
store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV3Cat, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8, !tbaa !4
%1 = bitcast i8* %call to %struct.Animal*
tail call void @_Z14doThingWithCatP6Animal(%struct.Animal* nonnull %1)
ret void
}
declare dso_local nonnull i8* @_Znwm(i64) local_unnamed_addr
declare dso_local void @_Z14doThingWithCatP6Animal(%struct.Animal*) local_unnamed_addr
!0 = !{i64 16, !"_ZTS3Cat"}
!1 = !{i64 16, !"_ZTSM3CatKFvvE.virtual"}
!2 = !{i64 16, !"_ZTS6Animal"}
!3 = !{i64 16, !"_ZTSM6AnimalKFvvE.virtual"}
!4 = !{!5, !5, i64 0}
!5 = !{!"vtable pointer", !6, i64 0}
!6 = !{!"Simple C++ TBAA"}