Author: hans Date: Fri Dec 7 00:17:26 2018 New Revision: 348569 URL: http://llvm.org/viewvc/llvm-project?rev=348569&view=rev Log: Fix thunks returning memptrs via sret by emitting also scalar return values directly in sret slot (PR39901)
Thunks that return member pointers via sret are broken due to using temporary storage for the return value on the stack and then passing that pointer to a tail call, violating the rule that a tail call can't access allocas in the caller (see bug). Since r90526, we put aggregate return values directly in the sret slot, but this doesn't apply to member pointers which are considered scalar. Unless I'm missing something subtle, we should be able to always use the sret slot directly for indirect return values. Differential revision: https://reviews.llvm.org/D55371 Added: cfe/trunk/test/CodeGenCXX/thunk-returning-memptr.cpp Modified: cfe/trunk/lib/CodeGen/CGVTables.cpp cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Modified: cfe/trunk/lib/CodeGen/CGVTables.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGVTables.cpp?rev=348569&r1=348568&r2=348569&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CGVTables.cpp (original) +++ cfe/trunk/lib/CodeGen/CGVTables.cpp Fri Dec 7 00:17:26 2018 @@ -350,8 +350,7 @@ void CodeGenFunction::EmitCallAndReturnF : FPT->getReturnType(); ReturnValueSlot Slot; if (!ResultType->isVoidType() && - CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect && - !hasScalarEvaluationKind(CurFnInfo->getReturnType())) + CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect) Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified()); // Now emit our call. Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=348569&r1=348568&r2=348569&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original) +++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Fri Dec 7 00:17:26 2018 @@ -1073,9 +1073,8 @@ void CodeGenFunction::StartFunction(Glob // Count the implicit return. if (!endsWithReturn(D)) ++NumReturnExprs; - } else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect && - !hasScalarEvaluationKind(CurFnInfo->getReturnType())) { - // Indirect aggregate return; emit returned value directly into sret slot. + } else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect) { + // Indirect return; emit returned value directly into sret slot. // This reduces code size, and affects correctness in C++. auto AI = CurFn->arg_begin(); if (CurFnInfo->getReturnInfo().isSRetAfterThis()) Added: cfe/trunk/test/CodeGenCXX/thunk-returning-memptr.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/thunk-returning-memptr.cpp?rev=348569&view=auto ============================================================================== --- cfe/trunk/test/CodeGenCXX/thunk-returning-memptr.cpp (added) +++ cfe/trunk/test/CodeGenCXX/thunk-returning-memptr.cpp Fri Dec 7 00:17:26 2018 @@ -0,0 +1,27 @@ +// RUN: %clang_cc1 -triple=i686 -emit-llvm -o - %s | FileCheck %s + + +struct X; +typedef void (X::*memptr)(); + +struct A { + virtual memptr f(); +}; + +struct B { + virtual memptr f(); +}; + +struct C : A, B { + C(); + memptr f() override __attribute__((noinline)) { return nullptr; }; +}; + +C::C() {} + +// Make sure the member pointer is returned from the thunk via the return slot. +// Because of the tail call, the return value cannot be copied into a local +// alloca. (PR39901) + +// CHECK-LABEL: define linkonce_odr void @_ZThn4_N1C1fEv({ i32, i32 }* noalias sret %agg.result, %struct.C* %this) +// CHECK: tail call void @_ZN1C1fEv({ i32, i32 }* sret %agg.result _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
