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zmodemzmodem
committedAug 28, 2015
Allow TLS vars in dllimport/export functions; only inline dllimport functions when safe (PR24593)
This patch does two things: 1) Don't error about dllimport/export on thread-local static local variables. We put those attributes on static locals in dllimport/export functions implicitly in case the function gets inlined. Now, for TLS variables this is a problem because we can't import such variables, but it's a benign problem becase: 2) Make sure we never inline a dllimport function TLS static locals. In fact, never inline a dllimport function that references a non-imported function or variable (because these are not defined in the importing library). This seems to match MSVC's behaviour. Differential Revision: http://reviews.llvm.org/D12422 llvm-svn: 246338
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‎clang/lib/CodeGen/CodeGenModule.cpp

Lines changed: 38 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1448,6 +1448,35 @@ namespace {
14481448
return true;
14491449
}
14501450
};
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struct DLLImportFunctionVisitor
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: public RecursiveASTVisitor<DLLImportFunctionVisitor> {
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bool SafeToInline = true;
1455+
1456+
bool VisitVarDecl(VarDecl *VD) {
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// A thread-local variable cannot be imported.
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SafeToInline = !VD->getTLSKind();
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return SafeToInline;
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}
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// Make sure we're not referencing non-imported vars or functions.
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bool VisitDeclRefExpr(DeclRefExpr *E) {
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ValueDecl *VD = E->getDecl();
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if (isa<FunctionDecl>(VD))
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SafeToInline = VD->hasAttr<DLLImportAttr>();
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else if (VarDecl *V = dyn_cast<VarDecl>(VD))
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SafeToInline = !V->hasGlobalStorage() || V->hasAttr<DLLImportAttr>();
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return SafeToInline;
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}
1471+
bool VisitCXXDeleteExpr(CXXDeleteExpr *E) {
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SafeToInline = E->getOperatorDelete()->hasAttr<DLLImportAttr>();
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return SafeToInline;
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}
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bool VisitCXXNewExpr(CXXNewExpr *E) {
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SafeToInline = E->getOperatorNew()->hasAttr<DLLImportAttr>();
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return SafeToInline;
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}
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};
14511480
}
14521481

14531482
// isTriviallyRecursive - Check if this function calls another
@@ -1478,6 +1507,15 @@ CodeGenModule::shouldEmitFunction(GlobalDecl GD) {
14781507
const auto *F = cast<FunctionDecl>(GD.getDecl());
14791508
if (CodeGenOpts.OptimizationLevel == 0 && !F->hasAttr<AlwaysInlineAttr>())
14801509
return false;
1510+
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if (F->hasAttr<DLLImportAttr>()) {
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// Check whether it would be safe to inline this dllimport function.
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DLLImportFunctionVisitor Visitor;
1514+
Visitor.TraverseFunctionDecl(const_cast<FunctionDecl*>(F));
1515+
if (!Visitor.SafeToInline)
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return false;
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}
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14811519
// PR9614. Avoid cases where the source code is lying to us. An available
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// externally function should have an equivalent function somewhere else,
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// but a function that calls itself is clearly not equivalent to the real

‎clang/lib/Sema/SemaDecl.cpp

Lines changed: 11 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -9967,9 +9967,17 @@ Sema::FinalizeDeclaration(Decl *ThisDecl) {
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// dllimport/dllexport variables cannot be thread local, their TLS index
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// isn't exported with the variable.
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if (DLLAttr && VD->getTLSKind()) {
9970-
Diag(VD->getLocation(), diag::err_attribute_dll_thread_local) << VD
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<< DLLAttr;
9972-
VD->setInvalidDecl();
9970+
FunctionDecl *F = dyn_cast<FunctionDecl>(VD->getDeclContext());
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if (F && getDLLAttr(F)) {
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assert(VD->isStaticLocal());
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// But if this is a static local in a dlimport/dllexport function, the
9974+
// function will never be inlined, which means the var would never be
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// imported, so having it marked import/export is safe.
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} else {
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Diag(VD->getLocation(), diag::err_attribute_dll_thread_local) << VD
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<< DLLAttr;
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VD->setInvalidDecl();
9980+
}
99739981
}
99749982

99759983
if (UsedAttr *Attr = VD->getAttr<UsedAttr>()) {

‎clang/test/CodeGenCXX/dllimport.cpp

Lines changed: 41 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -86,7 +86,7 @@ USEVAR(GlobalRedecl3)
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namespace ns { __declspec(dllimport) int ExternalGlobal; }
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USEVAR(ns::ExternalGlobal)
8888

89-
int f();
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int __declspec(dllimport) f();
9090
// MO1-DAG: @"\01?x@?1??inlineStaticLocalsFunc@@YAHXZ@4HA" = available_externally dllimport global i32 0
9191
// MO1-DAG: @"\01??_B?1??inlineStaticLocalsFunc@@YAHXZ@51" = available_externally dllimport global i32 0
9292
inline int __declspec(dllimport) inlineStaticLocalsFunc() {
@@ -314,6 +314,46 @@ void UNIQ(use)() { ::operator new(42); }
314314
namespace ns { __declspec(dllimport) void externalFunc(); }
315315
USE(ns::externalFunc)
316316

317+
// A dllimport function referencing non-imported vars or functions must not be available_externally.
318+
__declspec(dllimport) int ImportedVar;
319+
int NonImportedVar;
320+
__declspec(dllimport) int ImportedFunc();
321+
int NonImportedFunc();
322+
__declspec(dllimport) inline int ReferencingImportedVar() { return ImportedVar; }
323+
// MO1-DAG: define available_externally dllimport i32 @"\01?ReferencingImportedVar@@YAHXZ"
324+
__declspec(dllimport) inline int ReferencingNonImportedVar() { return NonImportedVar; }
325+
// MO1-DAG: declare dllimport i32 @"\01?ReferencingNonImportedVar@@YAHXZ"()
326+
__declspec(dllimport) inline int ReferencingImportedFunc() { return ImportedFunc(); }
327+
// MO1-DAG: define available_externally dllimport i32 @"\01?ReferencingImportedFunc@@YAHXZ"
328+
__declspec(dllimport) inline int ReferencingNonImportedFunc() { return NonImportedFunc(); }
329+
// MO1-DAG: declare dllimport i32 @"\01?ReferencingNonImportedFunc@@YAHXZ"()
330+
USE(ReferencingImportedVar)
331+
USE(ReferencingNonImportedVar)
332+
USE(ReferencingImportedFunc)
333+
USE(ReferencingNonImportedFunc)
334+
// References to operator new and delete count too, despite not being DeclRefExprs.
335+
__declspec(dllimport) inline int *ReferencingNonImportedNew() { return new int[2]; }
336+
// MO1-DAG: declare dllimport i32* @"\01?ReferencingNonImportedNew@@YAPAHXZ"
337+
__declspec(dllimport) inline int *ReferencingNonImportedDelete() { delete (int*)nullptr; }
338+
// MO1-DAG: declare dllimport i32* @"\01?ReferencingNonImportedDelete@@YAPAHXZ"
339+
USE(ReferencingNonImportedNew)
340+
USE(ReferencingNonImportedDelete)
341+
__declspec(dllimport) void* operator new[](__SIZE_TYPE__);
342+
__declspec(dllimport) void operator delete(void*);
343+
__declspec(dllimport) inline int *ReferencingImportedNew() { return new int[2]; }
344+
// MO1-DAG: define available_externally dllimport i32* @"\01?ReferencingImportedNew@@YAPAHXZ"
345+
__declspec(dllimport) inline int *ReferencingImportedDelete() { delete (int*)nullptr; }
346+
// MO1-DAG: define available_externally dllimport i32* @"\01?ReferencingImportedDelete@@YAPAHXZ"
347+
USE(ReferencingImportedNew)
348+
USE(ReferencingImportedDelete)
349+
350+
// A dllimport function with a TLS variable must not be available_externally.
351+
__declspec(dllimport) inline void FunctionWithTLSVar() { static __thread int x = 42; }
352+
// MO1-DAG: declare dllimport void @"\01?FunctionWithTLSVar@@YAXXZ"
353+
__declspec(dllimport) inline void FunctionWithNormalVar() { static int x = 42; }
354+
// MO1-DAG: define available_externally dllimport void @"\01?FunctionWithNormalVar@@YAXXZ"
355+
USE(FunctionWithTLSVar)
356+
USE(FunctionWithNormalVar)
317357

318358

319359
//===----------------------------------------------------------------------===//

‎clang/test/SemaCXX/dllexport.cpp

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -71,6 +71,15 @@ __declspec(dllexport) auto ExternalAutoTypeGlobal = External();
7171

7272
// Thread local variables are invalid.
7373
__declspec(dllexport) __thread int ThreadLocalGlobal; // expected-error{{'ThreadLocalGlobal' cannot be thread local when declared 'dllexport'}}
74+
inline void InlineWithThreadLocal() {
75+
static __declspec(dllexport) __thread int ThreadLocalGlobal; // expected-error{{'ThreadLocalGlobal' cannot be thread local when declared 'dllexport'}}
76+
}
77+
78+
// But if they're in a dllexport function, it's ok, because they will never get imported.
79+
inline void __declspec(dllexport) ExportedInlineWithThreadLocal() {
80+
static __declspec(dllexport) __thread int OK1; // no-error
81+
static __thread int OK2; // no-error
82+
}
7483

7584
// Export in local scope.
7685
void functionScope() {

‎clang/test/SemaCXX/dllimport.cpp

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -93,6 +93,18 @@ __declspec(dllimport) auto InternalAutoTypeGlobal = Internal(); // expected-erro
9393

9494
// Thread local variables are invalid.
9595
__declspec(dllimport) __thread int ThreadLocalGlobal; // expected-error{{'ThreadLocalGlobal' cannot be thread local when declared 'dllimport'}}
96+
inline void InlineWithThreadLocal() {
97+
static __declspec(dllimport) __thread int ThreadLocalGlobal; // expected-error{{'ThreadLocalGlobal' cannot be thread local when declared 'dllimport'}}
98+
}
99+
100+
// But if they're in a dllimported function, it's OK because we will not inline the function.
101+
// This doesn't work on MinGW, because there, dllimport on the inline function is ignored.
102+
#ifndef GNU
103+
inline void __declspec(dllimport) ImportedInlineWithThreadLocal() {
104+
static __declspec(dllimport) __thread int OK1; // no-error
105+
static __thread int OK2; // no-error
106+
}
107+
#endif
96108

97109
// Import in local scope.
98110
__declspec(dllimport) float LocalRedecl1; // expected-note{{previous declaration is here}}

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