From cd4d6d718b2e51ed830a28d01d765da2a220afd3 Mon Sep 17 00:00:00 2001 From: Richard Smith Date: Tue, 24 Aug 2021 18:34:38 -0700 Subject: [PATCH] PR48030: Fix COMDAT-related linking problem with C++ thread_local static data members. Previously when emitting a C++ guarded initializer, we tried to work out what the enclosing function would be used for and added it to the COMDAT containing the variable if we thought that doing so would be correct. But this was done from a context in which we didn't -- and realistically couldn't -- correctly infer how the enclosing function would be used. Instead, add the initialization function to a COMDAT from the code that creates it, in the case where it makes sense to do so: when we know that the one and only reference to the initialization function is in @llvm.global.ctors and that reference is in the same COMDAT. Reviewed By: rjmccall Differential Revision: https://reviews.llvm.org/D108680 --- clang/lib/CodeGen/CGDeclCXX.cpp | 10 +++++++ clang/lib/CodeGen/ItaniumCXXABI.cpp | 5 ---- .../cxx11-thread-local-instantiated.cpp | 26 +++++++++++++++++++ clang/test/CodeGenCXX/cxx11-thread-local.cpp | 12 +++------ .../CodeGenCXX/cxx1z-inline-variables.cpp | 4 +-- clang/test/OpenMP/threadprivate_codegen.cpp | 8 +++--- 6 files changed, 45 insertions(+), 20 deletions(-) create mode 100644 clang/test/CodeGenCXX/cxx11-thread-local-instantiated.cpp diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp index 553fedebfe56..d22f9dc3b68c 100644 --- a/clang/lib/CodeGen/CGDeclCXX.cpp +++ b/clang/lib/CodeGen/CGDeclCXX.cpp @@ -581,6 +581,16 @@ CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D, // llvm.used to prevent linker GC. addUsedGlobal(COMDATKey); } + + // If we used a COMDAT key for the global ctor, the init function can be + // discarded if the global ctor entry is discarded. + // FIXME: Do we need to restrict this to ELF and Wasm? + llvm::Comdat *C = Addr->getComdat(); + if (COMDATKey && C && + (getTarget().getTriple().isOSBinFormatELF() || + getTarget().getTriple().isOSBinFormatWasm())) { + Fn->setComdat(C); + } } else { I = DelayedCXXInitPosition.find(D); // Re-do lookup in case of re-hash. if (I == DelayedCXXInitPosition.end()) { diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp index d3dc0e6212b8..8ddc2f1885eb 100644 --- a/clang/lib/CodeGen/ItaniumCXXABI.cpp +++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp @@ -2445,11 +2445,6 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF, (CGM.getTarget().getTriple().isOSBinFormatELF() || CGM.getTarget().getTriple().isOSBinFormatWasm())) { guard->setComdat(C); - // An inline variable's guard function is run from the per-TU - // initialization function, not via a dedicated global ctor function, so - // we can't put it in a comdat. - if (!NonTemplateInline) - CGF.CurFn->setComdat(C); } else if (CGM.supportsCOMDAT() && guard->isWeakForLinker()) { guard->setComdat(CGM.getModule().getOrInsertComdat(guard->getName())); } diff --git a/clang/test/CodeGenCXX/cxx11-thread-local-instantiated.cpp b/clang/test/CodeGenCXX/cxx11-thread-local-instantiated.cpp new file mode 100644 index 000000000000..3c78c7f7df90 --- /dev/null +++ b/clang/test/CodeGenCXX/cxx11-thread-local-instantiated.cpp @@ -0,0 +1,26 @@ +// RUN: %clang_cc1 -std=c++11 -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s + +// PR48030 + +template struct TLS { static thread_local T *mData; }; +inline decltype(nullptr) non_constant_initializer() { return nullptr; } +template thread_local T *TLS::mData = non_constant_initializer(); +struct S {}; +S *current() { return TLS::mData; }; + +// CHECK-DAG: @_ZN3TLSI1SE5mDataE = linkonce_odr thread_local global {{.*}}, comdat, +// CHECK-DAG: @_ZGVN3TLSI1SE5mDataE = linkonce_odr thread_local global {{.*}}, comdat($_ZN3TLSI1SE5mDataE), +// CHECK-DAG: @_ZTHN3TLSI1SE5mDataE = linkonce_odr alias {{.*}} @__cxx_global_var_init + +// CHECK-LABEL: define {{.*}} @_Z7currentv() +// CHECK: call {{.*}} @_ZTWN3TLSI1SE5mDataE() + +// CHECK-LABEL: define weak_odr hidden {{.*}} @_ZTWN3TLSI1SE5mDataE() {{.*}} comdat { +// CHECK: call void @_ZTHN3TLSI1SE5mDataE() +// CHECK: ret {{.*}} @_ZN3TLSI1SE5mDataE + +// Unlike for a global, the global initialization function must not be in a +// COMDAT with the variable, because it is referenced from the _ZTH function +// which is outside that COMDAT. +// +// CHECK-NOT: define {{.*}} @__cxx_global_var_init{{.*}}comdat diff --git a/clang/test/CodeGenCXX/cxx11-thread-local.cpp b/clang/test/CodeGenCXX/cxx11-thread-local.cpp index f3146715b921..e63762ee7bfa 100644 --- a/clang/test/CodeGenCXX/cxx11-thread-local.cpp +++ b/clang/test/CodeGenCXX/cxx11-thread-local.cpp @@ -179,8 +179,7 @@ int f() { // LINUX_AIX: define internal void @[[VF_M_INIT]]() // DARWIN: define internal cxx_fast_tlscc void @[[VF_M_INIT]]() -// LINUX-SAME: comdat($_ZN1VIfE1mE) -// DARWIN-NOT: comdat +// CHECK-NOT: comdat // CHECK: load i8, i8* bitcast (i64* @_ZGVN1VIfE1mE to i8*) // CHECK: %[[VF_M_INITIALIZED:.*]] = icmp eq i8 %{{.*}}, 0 // CHECK: br i1 %[[VF_M_INITIALIZED]], @@ -192,8 +191,7 @@ int f() { // LINUX_AIX: define internal void @[[XF_M_INIT]]() // DARWIN: define internal cxx_fast_tlscc void @[[XF_M_INIT]]() -// LINUX-SAME: comdat($_ZN1XIfE1mE) -// DARWIN-NOT: comdat +// CHECK-NOT: comdat // CHECK: load i8, i8* bitcast (i64* @_ZGVN1XIfE1mE to i8*) // CHECK: %[[XF_M_INITIALIZED:.*]] = icmp eq i8 %{{.*}}, 0 // CHECK: br i1 %[[XF_M_INITIALIZED]], @@ -313,8 +311,7 @@ void set_anon_i() { // LINUX_AIX: define internal void @[[V_M_INIT]]() // DARWIN: define internal cxx_fast_tlscc void @[[V_M_INIT]]() -// LINUX-SAME: comdat($_ZN1VIiE1mE) -// DARWIN-NOT: comdat +// CHECK-NOT: comdat // CHECK: load i8, i8* bitcast (i64* @_ZGVN1VIiE1mE to i8*) // CHECK: %[[V_M_INITIALIZED:.*]] = icmp eq i8 %{{.*}}, 0 // CHECK: br i1 %[[V_M_INITIALIZED]], @@ -326,8 +323,7 @@ void set_anon_i() { // LINUX_AIX: define internal void @[[X_M_INIT]]() // DARWIN: define internal cxx_fast_tlscc void @[[X_M_INIT]]() -// LINUX-SAME: comdat($_ZN1XIiE1mE) -// DARWIN-NOT: comdat +// CHECK-NOT: comdat // CHECK: load i8, i8* bitcast (i64* @_ZGVN1XIiE1mE to i8*) // CHECK: %[[X_M_INITIALIZED:.*]] = icmp eq i8 %{{.*}}, 0 // CHECK: br i1 %[[X_M_INITIALIZED]], diff --git a/clang/test/CodeGenCXX/cxx1z-inline-variables.cpp b/clang/test/CodeGenCXX/cxx1z-inline-variables.cpp index a616e95a2be5..896db4acc131 100644 --- a/clang/test/CodeGenCXX/cxx1z-inline-variables.cpp +++ b/clang/test/CodeGenCXX/cxx1z-inline-variables.cpp @@ -90,9 +90,7 @@ const int &yib = Y::b; // CHECK-LABEL: define {{.*}}global_var_init // CHECK: call i32 @_Z1fv -// CHECK-LABEL: define {{.*}}global_var_init -// CHECK-NOT: comdat -// CHECK-SAME: {{$}} +// CHECK-LABEL: define {{.*}}global_var_init{{.*}} comdat($b) // CHECK: load atomic {{.*}} acquire, align // CHECK: br // CHECK: __cxa_guard_acquire(i64* @_ZGV1b) diff --git a/clang/test/OpenMP/threadprivate_codegen.cpp b/clang/test/OpenMP/threadprivate_codegen.cpp index c07ffe1a28cc..f1ccb80cb3ab 100644 --- a/clang/test/OpenMP/threadprivate_codegen.cpp +++ b/clang/test/OpenMP/threadprivate_codegen.cpp @@ -3847,7 +3847,7 @@ int foobar() { // // // CHECK-TLS1-LABEL: define {{[^@]+}}@__cxx_global_var_init.3 -// CHECK-TLS1-SAME: () #[[ATTR0]] comdat($_ZN2STI2S4E2stE) { +// CHECK-TLS1-SAME: () #[[ATTR0]] { // CHECK-TLS1-NEXT: entry: // CHECK-TLS1-NEXT: [[TMP0:%.*]] = load i8, i8* bitcast (i64* @_ZGVN2STI2S4E2stE to i8*), align 8 // CHECK-TLS1-NEXT: [[GUARD_UNINITIALIZED:%.*]] = icmp eq i8 [[TMP0]], 0 @@ -4373,7 +4373,7 @@ int foobar() { // // // CHECK-TLS2-LABEL: define {{[^@]+}}@__cxx_global_var_init.3 -// CHECK-TLS2-SAME: () #[[ATTR6]] comdat($_ZN2STI2S4E2stE) { +// CHECK-TLS2-SAME: () #[[ATTR6]] { // CHECK-TLS2-NEXT: entry: // CHECK-TLS2-NEXT: [[TMP0:%.*]] = load i8, i8* bitcast (i64* @_ZGVN2STI2S4E2stE to i8*), align 8 // CHECK-TLS2-NEXT: [[GUARD_UNINITIALIZED:%.*]] = icmp eq i8 [[TMP0]], 0 @@ -4906,7 +4906,7 @@ int foobar() { // // // CHECK-TLS3-LABEL: define {{[^@]+}}@__cxx_global_var_init.3 -// CHECK-TLS3-SAME: () #[[ATTR0]] comdat($_ZN2STI2S4E2stE) !dbg [[DBG289:![0-9]+]] { +// CHECK-TLS3-SAME: () #[[ATTR0]] !dbg [[DBG289:![0-9]+]] { // CHECK-TLS3-NEXT: entry: // CHECK-TLS3-NEXT: [[TMP0:%.*]] = load i8, i8* bitcast (i64* @_ZGVN2STI2S4E2stE to i8*), align 8, !dbg [[DBG290:![0-9]+]] // CHECK-TLS3-NEXT: [[GUARD_UNINITIALIZED:%.*]] = icmp eq i8 [[TMP0]], 0, !dbg [[DBG290]] @@ -5459,7 +5459,7 @@ int foobar() { // // // CHECK-TLS4-LABEL: define {{[^@]+}}@__cxx_global_var_init.3 -// CHECK-TLS4-SAME: () #[[ATTR7]] comdat($_ZN2STI2S4E2stE) !dbg [[DBG289:![0-9]+]] { +// CHECK-TLS4-SAME: () #[[ATTR7]] !dbg [[DBG289:![0-9]+]] { // CHECK-TLS4-NEXT: entry: // CHECK-TLS4-NEXT: [[TMP0:%.*]] = load i8, i8* bitcast (i64* @_ZGVN2STI2S4E2stE to i8*), align 8, !dbg [[DBG290:![0-9]+]] // CHECK-TLS4-NEXT: [[GUARD_UNINITIALIZED:%.*]] = icmp eq i8 [[TMP0]], 0, !dbg [[DBG290]]