diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 2b5121a7b23063..920a219205a21f 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -13,6 +13,7 @@ #include "CGCall.h" #include "ABIInfo.h" +#include "ABIInfoImpl.h" #include "CGBlocks.h" #include "CGCXXABI.h" #include "CGCleanup.h" @@ -5781,9 +5782,14 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo, DestIsVolatile = false; } - // If the value is offset in memory, apply the offset now. - Address StorePtr = emitAddressAtOffset(*this, DestPtr, RetAI); - CreateCoercedStore(CI, StorePtr, DestIsVolatile, *this); + // An empty record can overlap other data (if declared with + // no_unique_address); omit the store for such types - as there is no + // actual data to store. + if (!isEmptyRecord(getContext(), RetTy, true)) { + // If the value is offset in memory, apply the offset now. + Address StorePtr = emitAddressAtOffset(*this, DestPtr, RetAI); + CreateCoercedStore(CI, StorePtr, DestIsVolatile, *this); + } return convertTempToRValue(DestPtr, RetTy, SourceLocation()); } diff --git a/clang/test/CodeGenCXX/ctor-empty-nounique.cpp b/clang/test/CodeGenCXX/ctor-empty-nounique.cpp new file mode 100644 index 00000000000000..f01cad1dacf266 --- /dev/null +++ b/clang/test/CodeGenCXX/ctor-empty-nounique.cpp @@ -0,0 +1,47 @@ +// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm -o - %s | FileCheck %s +// RUN: %clang_cc1 -triple powerpc64le-windows-gnu -emit-llvm -o - %s | FileCheck %s + +// An empty struct is handled as a struct with a dummy i8, on all targets. +// Most targets treat an empty struct return value as essentially void - but +// some don't. (Currently, at least x86_64-windows-* and powerpc64le-* don't +// treat it as void.) +// +// When intializing a struct with such a no_unique_address member, make sure we +// don't write the dummy i8 into the struct where there's no space allocated for +// it. +// +// This can only be tested with targets that don't treat empty struct returns as +// void. + +struct S {}; +S f(); +struct Z { + int x; + [[no_unique_address]] S y; + Z(); +}; +Z::Z() : x(111), y(f()) {} + +// CHECK: define {{.*}} @_ZN1ZC2Ev +// CHECK: %call = call i8 @_Z1fv() +// CHECK-NEXT: ret void + + +// Check that the constructor for an empty member gets called with the right +// 'this' pointer. + +struct S2 { + S2(); +}; +struct Z2 { + int x; + [[no_unique_address]] S2 y; + Z2(); +}; +Z2::Z2() : x(111) {} + +// CHECK: define {{.*}} @_ZN2Z2C2Ev(ptr {{.*}} %this) +// CHECK: %this.addr = alloca ptr +// CHECK: store ptr %this, ptr %this.addr +// CHECK: %this1 = load ptr, ptr %this.addr +// CHECK: call void @_ZN2S2C1Ev(ptr {{.*}} %this1)