r338941 - [constexpr] Support for constant evaluation of __builtin_memcpy and
Tom Stellard via cfe-commits
cfe-commits at lists.llvm.org
Mon Nov 26 08:22:44 PST 2018
On 11/21/2018 03:32 PM, Shoaib Meenai wrote:
> If it's not too late, could we have this as part of 7.0.1? (You'll also need to cherry-pick the initial reversion in r338602.) 7.0 hits assertion failures for pretty basic memcpy cases on windows-msvc targets, and this patch fixes that.
>
I've created a bug to track this request: PR39791.
-Tom
> % cat /tmp/reduced.c
> void *memcpy(void *, const void *, __SIZE_TYPE__);
> void f(int i) {
> struct { int i } s;
> memcpy((char *)&s.i, &i, sizeof(i));
> }
>
> % clang -cc1 -triple x86_64-windows-msvc -emit-llvm -fms-compatibility -o /dev/null /tmp/reduced.c
> llvm::SmallVectorTemplateCommon::const_reference llvm::SmallVectorTemplateCommon<clang::APValue::LValuePathEntry, void>::back() const [T = clang::APValue::LValuePathEntry]: Assertion `!empty()' failed.
>
> On Fri, Aug 3, 2018 at 5:57 PM Richard Smith via cfe-commits <cfe-commits at lists.llvm.org <mailto:cfe-commits at lists.llvm.org>> wrote:
>
> Author: rsmith
> Date: Fri Aug 3 17:57:17 2018
> New Revision: 338941
>
> URL: http://llvm.org/viewvc/llvm-project?rev=338941&view=rev
> Log:
> [constexpr] Support for constant evaluation of __builtin_memcpy and
> __builtin_memmove (in non-type-punning cases).
>
> 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.
>
> This reinstates r338455, reverted in r338602, with a fix to avoid trying
> to constant-evaluate a memcpy call if either pointer operand has an
> invalid designator.
>
> 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=338941&r1=338940&r2=338941&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/Builtins.def (original)
> +++ cfe/trunk/include/clang/Basic/Builtins.def Fri Aug 3 17:57:17 2018
> @@ -471,6 +471,8 @@ 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")
> @@ -908,6 +910,8 @@ 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=338941&r1=338940&r2=338941&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticASTKinds.td Fri Aug 3 17:57:17 2018
> @@ -163,6 +163,20 @@ 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=338941&r1=338940&r2=338941&view=diff
> ==============================================================================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Fri Aug 3 17:57:17 2018
> @@ -319,6 +319,25 @@ 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)
> @@ -329,6 +348,14 @@ 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 {
> + assert(!Invalid && "invalid designator has no subobject type");
> + 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;
> @@ -1706,6 +1733,54 @@ 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*>();
> @@ -1917,33 +1992,6 @@ 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.
> @@ -6117,6 +6165,130 @@ 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)) || Result.Designator.Invalid)
> + return false;
> + LValue Dest = Result;
> +
> + LValue Src;
> + if (!EvaluatePointer(E->getArg(1), Src, Info) || Src.Designator.Invalid)
> + 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);
> }
> @@ -8357,27 +8529,6 @@ 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=338941&r1=338940&r2=338941&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/builtin-memfns.c (original)
> +++ cfe/trunk/test/CodeGen/builtin-memfns.c Fri Aug 3 17:57:17 2018
> @@ -1,5 +1,10 @@
> // RUN: %clang_cc1 -triple i386-pc-linux-gnu -emit-llvm < %s| FileCheck %s
>
> +typedef __WCHAR_TYPE__ wchar_t;
> +typedef __SIZE_TYPE__ size_t;
> +
> +void *memcpy(void *, void const *, size_t);
> +
> // CHECK: @test1
> // CHECK: call void @llvm.memset.p0i8.i32
> // CHECK: call void @llvm.memset.p0i8.i32
> @@ -83,3 +88,26 @@ 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);
> +}
> +
> +// CHECK-LABEL: @test11
> +void test11() {
> + typedef struct { int a; } b;
> + int d;
> + b e;
> + // CHECK: call void @llvm.memcpy{{.*}}(
> + memcpy(&d, (char *)&e.a, sizeof(e));
> +}
> +
>
> Modified: cfe/trunk/test/SemaCXX/constexpr-string.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constexpr-string.cpp?rev=338941&r1=338940&r2=338941&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/constexpr-string.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constexpr-string.cpp Fri Aug 3 17:57:17 2018
> @@ -1,6 +1,6 @@
> -// 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__
> +// 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__
>
> # 6 "/usr/include/string.h" 1 3 4
> extern "C" {
> @@ -14,10 +14,13 @@ 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);
> }
> -# 19 "SemaCXX/constexpr-string.cpp" 2
> +# 22 "SemaCXX/constexpr-string.cpp" 2
>
> -# 21 "/usr/include/wchar.h" 1 3 4
> +# 24 "/usr/include/wchar.h" 1 3 4
> extern "C" {
> extern size_t wcslen(const wchar_t *p);
>
> @@ -27,9 +30,12 @@ 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);
> }
>
> -# 33 "SemaCXX/constexpr-string.cpp" 2
> +# 39 "SemaCXX/constexpr-string.cpp" 2
> namespace Strlen {
> constexpr int n = __builtin_strlen("hello"); // ok
> static_assert(n == 5);
> @@ -235,3 +241,133 @@ 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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