r338602 - Revert r338455 "[constexpr] Support for constant evaluation of __builtin_memcpy and __builtin_memmove (in non-type-punning cases)."
Hans Wennborg via cfe-commits
cfe-commits at lists.llvm.org
Wed Aug 1 23:35:05 PDT 2018
Merged to 7.0 in r338674.
On Wed, Aug 1, 2018 at 7:51 PM, Hans Wennborg via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: hans
> Date: Wed Aug 1 10:51:23 2018
> New Revision: 338602
>
> URL: http://llvm.org/viewvc/llvm-project?rev=338602&view=rev
> Log:
> Revert r338455 "[constexpr] Support for constant evaluation of __builtin_memcpy and __builtin_memmove (in non-type-punning cases)."
>
> It caused asserts during Chromium builds, see reply on the cfe-commits thread.
>
>> This is intended to permit libc++ to make std::copy etc constexpr
>> without sacrificing the optimization that uses memcpy on
>> trivially-copyable types.
>>
>> __builtin_strcpy and __builtin_wcscpy are not handled by this change.
>> They'd be straightforward to add, but we haven't encountered a need for
>> them just yet.
>
> Modified:
> cfe/trunk/include/clang/Basic/Builtins.def
> cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td
> cfe/trunk/lib/AST/ExprConstant.cpp
> cfe/trunk/test/CodeGen/builtin-memfns.c
> cfe/trunk/test/SemaCXX/constexpr-string.cpp
>
> Modified: cfe/trunk/include/clang/Basic/Builtins.def
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Builtins.def?rev=338602&r1=338601&r2=338602&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/Builtins.def (original)
> +++ cfe/trunk/include/clang/Basic/Builtins.def Wed Aug 1 10:51:23 2018
> @@ -471,8 +471,6 @@ BUILTIN(__builtin_wcslen, "zwC*", "nF")
> BUILTIN(__builtin_wcsncmp, "iwC*wC*z", "nF")
> BUILTIN(__builtin_wmemchr, "w*wC*wz", "nF")
> BUILTIN(__builtin_wmemcmp, "iwC*wC*z", "nF")
> -BUILTIN(__builtin_wmemcpy, "w*w*wC*z", "nF")
> -BUILTIN(__builtin_wmemmove, "w*w*wC*z", "nF")
> BUILTIN(__builtin_return_address, "v*IUi", "n")
> BUILTIN(__builtin_extract_return_addr, "v*v*", "n")
> BUILTIN(__builtin_frame_address, "v*IUi", "n")
> @@ -910,8 +908,6 @@ LIBBUILTIN(wcslen, "zwC*", "f", "wc
> LIBBUILTIN(wcsncmp, "iwC*wC*z", "f", "wchar.h", ALL_LANGUAGES)
> LIBBUILTIN(wmemchr, "w*wC*wz", "f", "wchar.h", ALL_LANGUAGES)
> LIBBUILTIN(wmemcmp, "iwC*wC*z", "f", "wchar.h", ALL_LANGUAGES)
> -LIBBUILTIN(wmemcpy, "w*w*wC*z", "f", "wchar.h", ALL_LANGUAGES)
> -LIBBUILTIN(wmemmove,"w*w*wC*z", "f", "wchar.h", ALL_LANGUAGES)
>
> // C99
> // In some systems setjmp is a macro that expands to _setjmp. We undefine
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td?rev=338602&r1=338601&r2=338602&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td Wed Aug 1 10:51:23 2018
> @@ -163,20 +163,6 @@ def note_constexpr_unsupported_unsized_a
> def note_constexpr_unsized_array_indexed : Note<
> "indexing of array without known bound is not allowed "
> "in a constant expression">;
> -def note_constexpr_memcpy_type_pun : Note<
> - "cannot constant evaluate '%select{memcpy|memmove}0' from object of "
> - "type %1 to object of type %2">;
> -def note_constexpr_memcpy_nontrivial : Note<
> - "cannot constant evaluate '%select{memcpy|memmove}0' between objects of "
> - "non-trivially-copyable type %1">;
> -def note_constexpr_memcpy_overlap : Note<
> - "'%select{memcpy|wmemcpy}0' between overlapping memory regions">;
> -def note_constexpr_memcpy_unsupported : Note<
> - "'%select{%select{memcpy|wmemcpy}1|%select{memmove|wmemmove}1}0' "
> - "not supported: %select{"
> - "size to copy (%4) is not a multiple of size of element type %3 (%5)|"
> - "source is not a contiguous array of at least %4 elements of type %3|"
> - "destination is not a contiguous array of at least %4 elements of type %3}2">;
>
> def warn_integer_constant_overflow : Warning<
> "overflow in expression; result is %0 with type %1">,
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=338602&r1=338601&r2=338602&view=diff
> ==============================================================================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Wed Aug 1 10:51:23 2018
> @@ -319,25 +319,6 @@ namespace {
> return false;
> }
>
> - /// Get the range of valid index adjustments in the form
> - /// {maximum value that can be subtracted from this pointer,
> - /// maximum value that can be added to this pointer}
> - std::pair<uint64_t, uint64_t> validIndexAdjustments() {
> - if (Invalid || isMostDerivedAnUnsizedArray())
> - return {0, 0};
> -
> - // [expr.add]p4: For the purposes of these operators, a pointer to a
> - // nonarray object behaves the same as a pointer to the first element of
> - // an array of length one with the type of the object as its element type.
> - bool IsArray = MostDerivedPathLength == Entries.size() &&
> - MostDerivedIsArrayElement;
> - uint64_t ArrayIndex =
> - IsArray ? Entries.back().ArrayIndex : (uint64_t)IsOnePastTheEnd;
> - uint64_t ArraySize =
> - IsArray ? getMostDerivedArraySize() : (uint64_t)1;
> - return {ArrayIndex, ArraySize - ArrayIndex};
> - }
> -
> /// Check that this refers to a valid subobject.
> bool isValidSubobject() const {
> if (Invalid)
> @@ -348,13 +329,6 @@ namespace {
> /// relevant diagnostic and set the designator as invalid.
> bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
>
> - /// Get the type of the designated object.
> - QualType getType(ASTContext &Ctx) const {
> - return MostDerivedPathLength == Entries.size()
> - ? MostDerivedType
> - : Ctx.getRecordType(getAsBaseClass(Entries.back()));
> - }
> -
> /// Update this designator to refer to the first element within this array.
> void addArrayUnchecked(const ConstantArrayType *CAT) {
> PathEntry Entry;
> @@ -1732,54 +1706,6 @@ static bool IsGlobalLValue(APValue::LVal
> }
> }
>
> -static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
> - return LVal.Base.dyn_cast<const ValueDecl*>();
> -}
> -
> -static bool IsLiteralLValue(const LValue &Value) {
> - if (Value.getLValueCallIndex())
> - return false;
> - const Expr *E = Value.Base.dyn_cast<const Expr*>();
> - return E && !isa<MaterializeTemporaryExpr>(E);
> -}
> -
> -static bool IsWeakLValue(const LValue &Value) {
> - const ValueDecl *Decl = GetLValueBaseDecl(Value);
> - return Decl && Decl->isWeak();
> -}
> -
> -static bool isZeroSized(const LValue &Value) {
> - const ValueDecl *Decl = GetLValueBaseDecl(Value);
> - if (Decl && isa<VarDecl>(Decl)) {
> - QualType Ty = Decl->getType();
> - if (Ty->isArrayType())
> - return Ty->isIncompleteType() ||
> - Decl->getASTContext().getTypeSize(Ty) == 0;
> - }
> - return false;
> -}
> -
> -static bool HasSameBase(const LValue &A, const LValue &B) {
> - if (!A.getLValueBase())
> - return !B.getLValueBase();
> - if (!B.getLValueBase())
> - return false;
> -
> - if (A.getLValueBase().getOpaqueValue() !=
> - B.getLValueBase().getOpaqueValue()) {
> - const Decl *ADecl = GetLValueBaseDecl(A);
> - if (!ADecl)
> - return false;
> - const Decl *BDecl = GetLValueBaseDecl(B);
> - if (!BDecl || ADecl->getCanonicalDecl() != BDecl->getCanonicalDecl())
> - return false;
> - }
> -
> - return IsGlobalLValue(A.getLValueBase()) ||
> - (A.getLValueCallIndex() == B.getLValueCallIndex() &&
> - A.getLValueVersion() == B.getLValueVersion());
> -}
> -
> static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
> assert(Base && "no location for a null lvalue");
> const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
> @@ -1991,6 +1917,33 @@ CheckConstantExpression(EvalInfo &Info,
> return true;
> }
>
> +static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
> + return LVal.Base.dyn_cast<const ValueDecl*>();
> +}
> +
> +static bool IsLiteralLValue(const LValue &Value) {
> + if (Value.getLValueCallIndex())
> + return false;
> + const Expr *E = Value.Base.dyn_cast<const Expr*>();
> + return E && !isa<MaterializeTemporaryExpr>(E);
> +}
> +
> +static bool IsWeakLValue(const LValue &Value) {
> + const ValueDecl *Decl = GetLValueBaseDecl(Value);
> + return Decl && Decl->isWeak();
> +}
> +
> +static bool isZeroSized(const LValue &Value) {
> + const ValueDecl *Decl = GetLValueBaseDecl(Value);
> + if (Decl && isa<VarDecl>(Decl)) {
> + QualType Ty = Decl->getType();
> + if (Ty->isArrayType())
> + return Ty->isIncompleteType() ||
> + Decl->getASTContext().getTypeSize(Ty) == 0;
> + }
> + return false;
> +}
> +
> static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
> // A null base expression indicates a null pointer. These are always
> // evaluatable, and they are false unless the offset is zero.
> @@ -6164,130 +6117,6 @@ bool PointerExprEvaluator::VisitBuiltinC
> return ZeroInitialization(E);
> }
>
> - case Builtin::BImemcpy:
> - case Builtin::BImemmove:
> - case Builtin::BIwmemcpy:
> - case Builtin::BIwmemmove:
> - if (Info.getLangOpts().CPlusPlus11)
> - Info.CCEDiag(E, diag::note_constexpr_invalid_function)
> - << /*isConstexpr*/0 << /*isConstructor*/0
> - << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
> - else
> - Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
> - LLVM_FALLTHROUGH;
> - case Builtin::BI__builtin_memcpy:
> - case Builtin::BI__builtin_memmove:
> - case Builtin::BI__builtin_wmemcpy:
> - case Builtin::BI__builtin_wmemmove: {
> - bool WChar = BuiltinOp == Builtin::BIwmemcpy ||
> - BuiltinOp == Builtin::BIwmemmove ||
> - BuiltinOp == Builtin::BI__builtin_wmemcpy ||
> - BuiltinOp == Builtin::BI__builtin_wmemmove;
> - bool Move = BuiltinOp == Builtin::BImemmove ||
> - BuiltinOp == Builtin::BIwmemmove ||
> - BuiltinOp == Builtin::BI__builtin_memmove ||
> - BuiltinOp == Builtin::BI__builtin_wmemmove;
> -
> - // The result of mem* is the first argument.
> - if (!Visit(E->getArg(0)))
> - return false;
> - LValue Dest = Result;
> -
> - LValue Src;
> - if (!EvaluatePointer(E->getArg(1), Src, Info))
> - return false;
> -
> - APSInt N;
> - if (!EvaluateInteger(E->getArg(2), N, Info))
> - return false;
> - assert(!N.isSigned() && "memcpy and friends take an unsigned size");
> -
> - // If the size is zero, we treat this as always being a valid no-op.
> - // (Even if one of the src and dest pointers is null.)
> - if (!N)
> - return true;
> -
> - // We require that Src and Dest are both pointers to arrays of
> - // trivially-copyable type. (For the wide version, the designator will be
> - // invalid if the designated object is not a wchar_t.)
> - QualType T = Dest.Designator.getType(Info.Ctx);
> - QualType SrcT = Src.Designator.getType(Info.Ctx);
> - if (!Info.Ctx.hasSameUnqualifiedType(T, SrcT)) {
> - Info.FFDiag(E, diag::note_constexpr_memcpy_type_pun) << Move << SrcT << T;
> - return false;
> - }
> - if (!T.isTriviallyCopyableType(Info.Ctx)) {
> - Info.FFDiag(E, diag::note_constexpr_memcpy_nontrivial) << Move << T;
> - return false;
> - }
> -
> - // Figure out how many T's we're copying.
> - uint64_t TSize = Info.Ctx.getTypeSizeInChars(T).getQuantity();
> - if (!WChar) {
> - uint64_t Remainder;
> - llvm::APInt OrigN = N;
> - llvm::APInt::udivrem(OrigN, TSize, N, Remainder);
> - if (Remainder) {
> - Info.FFDiag(E, diag::note_constexpr_memcpy_unsupported)
> - << Move << WChar << 0 << T << OrigN.toString(10, /*Signed*/false)
> - << (unsigned)TSize;
> - return false;
> - }
> - }
> -
> - // Check that the copying will remain within the arrays, just so that we
> - // can give a more meaningful diagnostic. This implicitly also checks that
> - // N fits into 64 bits.
> - uint64_t RemainingSrcSize = Src.Designator.validIndexAdjustments().second;
> - uint64_t RemainingDestSize = Dest.Designator.validIndexAdjustments().second;
> - if (N.ugt(RemainingSrcSize) || N.ugt(RemainingDestSize)) {
> - Info.FFDiag(E, diag::note_constexpr_memcpy_unsupported)
> - << Move << WChar << (N.ugt(RemainingSrcSize) ? 1 : 2) << T
> - << N.toString(10, /*Signed*/false);
> - return false;
> - }
> - uint64_t NElems = N.getZExtValue();
> - uint64_t NBytes = NElems * TSize;
> -
> - // Check for overlap.
> - int Direction = 1;
> - if (HasSameBase(Src, Dest)) {
> - uint64_t SrcOffset = Src.getLValueOffset().getQuantity();
> - uint64_t DestOffset = Dest.getLValueOffset().getQuantity();
> - if (DestOffset >= SrcOffset && DestOffset - SrcOffset < NBytes) {
> - // Dest is inside the source region.
> - if (!Move) {
> - Info.FFDiag(E, diag::note_constexpr_memcpy_overlap) << WChar;
> - return false;
> - }
> - // For memmove and friends, copy backwards.
> - if (!HandleLValueArrayAdjustment(Info, E, Src, T, NElems - 1) ||
> - !HandleLValueArrayAdjustment(Info, E, Dest, T, NElems - 1))
> - return false;
> - Direction = -1;
> - } else if (!Move && SrcOffset >= DestOffset &&
> - SrcOffset - DestOffset < NBytes) {
> - // Src is inside the destination region for memcpy: invalid.
> - Info.FFDiag(E, diag::note_constexpr_memcpy_overlap) << WChar;
> - return false;
> - }
> - }
> -
> - while (true) {
> - APValue Val;
> - if (!handleLValueToRValueConversion(Info, E, T, Src, Val) ||
> - !handleAssignment(Info, E, Dest, T, Val))
> - return false;
> - // Do not iterate past the last element; if we're copying backwards, that
> - // might take us off the start of the array.
> - if (--NElems == 0)
> - return true;
> - if (!HandleLValueArrayAdjustment(Info, E, Src, T, Direction) ||
> - !HandleLValueArrayAdjustment(Info, E, Dest, T, Direction))
> - return false;
> - }
> - }
> -
> default:
> return visitNonBuiltinCallExpr(E);
> }
> @@ -8528,6 +8357,27 @@ bool IntExprEvaluator::VisitBuiltinCallE
> }
> }
>
> +static bool HasSameBase(const LValue &A, const LValue &B) {
> + if (!A.getLValueBase())
> + return !B.getLValueBase();
> + if (!B.getLValueBase())
> + return false;
> +
> + if (A.getLValueBase().getOpaqueValue() !=
> + B.getLValueBase().getOpaqueValue()) {
> + const Decl *ADecl = GetLValueBaseDecl(A);
> + if (!ADecl)
> + return false;
> + const Decl *BDecl = GetLValueBaseDecl(B);
> + if (!BDecl || ADecl->getCanonicalDecl() != BDecl->getCanonicalDecl())
> + return false;
> + }
> +
> + return IsGlobalLValue(A.getLValueBase()) ||
> + (A.getLValueCallIndex() == B.getLValueCallIndex() &&
> + A.getLValueVersion() == B.getLValueVersion());
> +}
> +
> /// Determine whether this is a pointer past the end of the complete
> /// object referred to by the lvalue.
> static bool isOnePastTheEndOfCompleteObject(const ASTContext &Ctx,
>
> Modified: cfe/trunk/test/CodeGen/builtin-memfns.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/builtin-memfns.c?rev=338602&r1=338601&r2=338602&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/builtin-memfns.c (original)
> +++ cfe/trunk/test/CodeGen/builtin-memfns.c Wed Aug 1 10:51:23 2018
> @@ -1,8 +1,5 @@
> // RUN: %clang_cc1 -triple i386-pc-linux-gnu -emit-llvm < %s| FileCheck %s
>
> -typedef __WCHAR_TYPE__ wchar_t;
> -typedef __SIZE_TYPE__ size_t;
> -
> // CHECK: @test1
> // CHECK: call void @llvm.memset.p0i8.i32
> // CHECK: call void @llvm.memset.p0i8.i32
> @@ -86,17 +83,3 @@ void test9() {
> // CHECK: call void @llvm.memcpy{{.*}} align 16 {{.*}} align 16 {{.*}} 16, i1 false)
> __builtin_memcpy(x, y, sizeof(y));
> }
> -
> -wchar_t dest;
> -wchar_t src;
> -
> -// CHECK-LABEL: @test10
> -// FIXME: Consider lowering these to llvm.memcpy / llvm.memmove.
> -void test10() {
> - // CHECK: call i32* @wmemcpy(i32* @dest, i32* @src, i32 4)
> - __builtin_wmemcpy(&dest, &src, 4);
> -
> - // CHECK: call i32* @wmemmove(i32* @dest, i32* @src, i32 4)
> - __builtin_wmemmove(&dest, &src, 4);
> -}
> -
>
> Modified: cfe/trunk/test/SemaCXX/constexpr-string.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constexpr-string.cpp?rev=338602&r1=338601&r2=338602&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/constexpr-string.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constexpr-string.cpp Wed Aug 1 10:51:23 2018
> @@ -1,6 +1,6 @@
> -// RUN: %clang_cc1 %s -triple x86_64-linux-gnu -std=c++1z -fsyntax-only -verify -pedantic
> -// RUN: %clang_cc1 %s -triple x86_64-linux-gnu -std=c++1z -fsyntax-only -verify -pedantic -fno-signed-char
> -// RUN: %clang_cc1 %s -triple x86_64-linux-gnu -std=c++1z -fsyntax-only -verify -pedantic -fno-wchar -Dwchar_t=__WCHAR_TYPE__
> +// RUN: %clang_cc1 %s -std=c++1z -fsyntax-only -verify -pedantic
> +// RUN: %clang_cc1 %s -std=c++1z -fsyntax-only -verify -pedantic -fno-signed-char
> +// RUN: %clang_cc1 %s -std=c++1z -fsyntax-only -verify -pedantic -fno-wchar -Dwchar_t=__WCHAR_TYPE__
>
> # 6 "/usr/include/string.h" 1 3 4
> extern "C" {
> @@ -14,13 +14,10 @@ extern "C" {
>
> extern char *strchr(const char *s, int c);
> extern void *memchr(const void *s, int c, size_t n);
> -
> - extern void *memcpy(void *d, const void *s, size_t n);
> - extern void *memmove(void *d, const void *s, size_t n);
> }
> -# 22 "SemaCXX/constexpr-string.cpp" 2
> +# 19 "SemaCXX/constexpr-string.cpp" 2
>
> -# 24 "/usr/include/wchar.h" 1 3 4
> +# 21 "/usr/include/wchar.h" 1 3 4
> extern "C" {
> extern size_t wcslen(const wchar_t *p);
>
> @@ -30,12 +27,9 @@ extern "C" {
>
> extern wchar_t *wcschr(const wchar_t *s, wchar_t c);
> extern wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
> -
> - extern wchar_t *wmemcpy(wchar_t *d, const wchar_t *s, size_t n);
> - extern wchar_t *wmemmove(wchar_t *d, const wchar_t *s, size_t n);
> }
>
> -# 39 "SemaCXX/constexpr-string.cpp" 2
> +# 33 "SemaCXX/constexpr-string.cpp" 2
> namespace Strlen {
> constexpr int n = __builtin_strlen("hello"); // ok
> static_assert(n == 5);
> @@ -241,133 +235,3 @@ namespace WcschrEtc {
> constexpr bool a = !wcschr(L"hello", L'h'); // expected-error {{constant expression}} expected-note {{non-constexpr function 'wcschr' cannot be used in a constant expression}}
> constexpr bool b = !wmemchr(L"hello", L'h', 3); // expected-error {{constant expression}} expected-note {{non-constexpr function 'wmemchr' cannot be used in a constant expression}}
> }
> -
> -namespace MemcpyEtc {
> - template<typename T>
> - constexpr T result(T (&arr)[4]) {
> - return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3];
> - }
> -
> - constexpr int test_memcpy(int a, int b, int n) {
> - int arr[4] = {1, 2, 3, 4};
> - __builtin_memcpy(arr + a, arr + b, n);
> - // expected-note at -1 2{{overlapping memory regions}}
> - // expected-note at -2 {{size to copy (1) is not a multiple of size of element type 'int'}}
> - // expected-note at -3 {{source is not a contiguous array of at least 2 elements of type 'int'}}
> - // expected-note at -4 {{destination is not a contiguous array of at least 3 elements of type 'int'}}
> - return result(arr);
> - }
> - constexpr int test_memmove(int a, int b, int n) {
> - int arr[4] = {1, 2, 3, 4};
> - __builtin_memmove(arr + a, arr + b, n);
> - // expected-note at -1 {{size to copy (1) is not a multiple of size of element type 'int'}}
> - // expected-note at -2 {{source is not a contiguous array of at least 2 elements of type 'int'}}
> - // expected-note at -3 {{destination is not a contiguous array of at least 3 elements of type 'int'}}
> - return result(arr);
> - }
> - constexpr int test_wmemcpy(int a, int b, int n) {
> - wchar_t arr[4] = {1, 2, 3, 4};
> - __builtin_wmemcpy(arr + a, arr + b, n);
> - // expected-note at -1 2{{overlapping memory regions}}
> - // expected-note-re at -2 {{source is not a contiguous array of at least 2 elements of type '{{wchar_t|int}}'}}
> - // expected-note-re at -3 {{destination is not a contiguous array of at least 3 elements of type '{{wchar_t|int}}'}}
> - return result(arr);
> - }
> - constexpr int test_wmemmove(int a, int b, int n) {
> - wchar_t arr[4] = {1, 2, 3, 4};
> - __builtin_wmemmove(arr + a, arr + b, n);
> - // expected-note-re at -1 {{source is not a contiguous array of at least 2 elements of type '{{wchar_t|int}}'}}
> - // expected-note-re at -2 {{destination is not a contiguous array of at least 3 elements of type '{{wchar_t|int}}'}}
> - return result(arr);
> - }
> -
> - static_assert(test_memcpy(1, 2, 4) == 1334);
> - static_assert(test_memcpy(2, 1, 4) == 1224);
> - static_assert(test_memcpy(0, 1, 8) == 2334); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memcpy(1, 0, 8) == 1124); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memcpy(1, 2, 1) == 1334); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memcpy(0, 3, 4) == 4234);
> - static_assert(test_memcpy(0, 3, 8) == 4234); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memcpy(2, 0, 12) == 4234); // expected-error {{constant}} expected-note {{in call}}
> -
> - static_assert(test_memmove(1, 2, 4) == 1334);
> - static_assert(test_memmove(2, 1, 4) == 1224);
> - static_assert(test_memmove(0, 1, 8) == 2334);
> - static_assert(test_memmove(1, 0, 8) == 1124);
> - static_assert(test_memmove(1, 2, 1) == 1334); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memmove(0, 3, 4) == 4234);
> - static_assert(test_memmove(0, 3, 8) == 4234); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_memmove(2, 0, 12) == 4234); // expected-error {{constant}} expected-note {{in call}}
> -
> - static_assert(test_wmemcpy(1, 2, 1) == 1334);
> - static_assert(test_wmemcpy(2, 1, 1) == 1224);
> - static_assert(test_wmemcpy(0, 1, 2) == 2334); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_wmemcpy(1, 0, 2) == 1124); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_wmemcpy(1, 2, 1) == 1334);
> - static_assert(test_wmemcpy(0, 3, 1) == 4234);
> - static_assert(test_wmemcpy(0, 3, 2) == 4234); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_wmemcpy(2, 0, 3) == 4234); // expected-error {{constant}} expected-note {{in call}}
> -
> - static_assert(test_wmemmove(1, 2, 1) == 1334);
> - static_assert(test_wmemmove(2, 1, 1) == 1224);
> - static_assert(test_wmemmove(0, 1, 2) == 2334);
> - static_assert(test_wmemmove(1, 0, 2) == 1124);
> - static_assert(test_wmemmove(1, 2, 1) == 1334);
> - static_assert(test_wmemmove(0, 3, 1) == 4234);
> - static_assert(test_wmemmove(0, 3, 2) == 4234); // expected-error {{constant}} expected-note {{in call}}
> - static_assert(test_wmemmove(2, 0, 3) == 4234); // expected-error {{constant}} expected-note {{in call}}
> -
> - // Copying is permitted for any trivially-copyable type.
> - struct Trivial { char k; short s; constexpr bool ok() { return k == 3 && s == 4; } };
> - constexpr bool test_trivial() {
> - Trivial arr[3] = {{1, 2}, {3, 4}, {5, 6}};
> - __builtin_memcpy(arr, arr+1, sizeof(Trivial));
> - __builtin_memmove(arr+1, arr, 2 * sizeof(Trivial));
> - return arr[0].ok() && arr[1].ok() && arr[2].ok();
> - }
> - static_assert(test_trivial());
> -
> - // But not for a non-trivially-copyable type.
> - struct NonTrivial {
> - constexpr NonTrivial() : n(0) {}
> - constexpr NonTrivial(const NonTrivial &) : n(1) {}
> - int n;
> - };
> - constexpr bool test_nontrivial_memcpy() { // expected-error {{never produces a constant}}
> - NonTrivial arr[3] = {};
> - __builtin_memcpy(arr, arr + 1, sizeof(NonTrivial)); // expected-note 2{{non-trivially-copyable}}
> - return true;
> - }
> - static_assert(test_nontrivial_memcpy()); // expected-error {{constant}} expected-note {{in call}}
> - constexpr bool test_nontrivial_memmove() { // expected-error {{never produces a constant}}
> - NonTrivial arr[3] = {};
> - __builtin_memcpy(arr, arr + 1, sizeof(NonTrivial)); // expected-note 2{{non-trivially-copyable}}
> - return true;
> - }
> - static_assert(test_nontrivial_memmove()); // expected-error {{constant}} expected-note {{in call}}
> -
> - // Type puns via constant evaluated memcpy are not supported yet.
> - constexpr float type_pun(const unsigned &n) {
> - float f = 0.0f;
> - __builtin_memcpy(&f, &n, 4); // expected-note {{cannot constant evaluate 'memcpy' from object of type 'const unsigned int' to object of type 'float'}}
> - return f;
> - }
> - static_assert(type_pun(0x3f800000) == 1.0f); // expected-error {{constant}} expected-note {{in call}}
> -
> - // Make sure we're not confused by derived-to-base conversions.
> - struct Base { int a; };
> - struct Derived : Base { int b; };
> - constexpr int test_derived_to_base(int n) {
> - Derived arr[2] = {1, 2, 3, 4};
> - Base *p = &arr[0];
> - Base *q = &arr[1];
> - __builtin_memcpy(p, q, sizeof(Base) * n); // expected-note {{source is not a contiguous array of at least 2 elements of type 'MemcpyEtc::Base'}}
> - return arr[0].a * 1000 + arr[0].b * 100 + arr[1].a * 10 + arr[1].b;
> - }
> - static_assert(test_derived_to_base(0) == 1234);
> - static_assert(test_derived_to_base(1) == 3234);
> - // FIXME: We could consider making this work by stripping elements off both
> - // designators until we have a long enough matching size, if both designators
> - // point to the start of their respective final elements.
> - static_assert(test_derived_to_base(2) == 3434); // expected-error {{constant}} expected-note {{in call}}
> -}
>
>
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