From db9b7f32ca3b6dc7f576b8e75834fb6277c01a19 Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Wed, 1 Aug 2018 17:51:23 +0000 Subject: [PATCH] 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. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@338602 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/clang/Basic/Builtins.def | 4 - include/clang/Basic/DiagnosticASTKinds.td | 14 -- lib/AST/ExprConstant.cpp | 246 +++++----------------- test/CodeGen/builtin-memfns.c | 17 -- test/SemaCXX/constexpr-string.cpp | 148 +------------ 5 files changed, 54 insertions(+), 375 deletions(-) diff --git a/include/clang/Basic/Builtins.def b/include/clang/Basic/Builtins.def index c4d11cd827..9089ce1b65 100644 --- a/include/clang/Basic/Builtins.def +++ b/include/clang/Basic/Builtins.def @@ -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", "wchar.h", ALL_LANGUAGES) 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 diff --git a/include/clang/Basic/DiagnosticASTKinds.td b/include/clang/Basic/DiagnosticASTKinds.td index 3358fc3d70..587254367b 100644 --- a/include/clang/Basic/DiagnosticASTKinds.td +++ b/include/clang/Basic/DiagnosticASTKinds.td @@ -163,20 +163,6 @@ def note_constexpr_unsupported_unsized_array : Note< 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">, diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp index 44cf75dbd2..25817b475c 100644 --- a/lib/AST/ExprConstant.cpp +++ b/lib/AST/ExprConstant.cpp @@ -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 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::LValueBase B) { } } -static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) { - return LVal.Base.dyn_cast(); -} - -static bool IsLiteralLValue(const LValue &Value) { - if (Value.getLValueCallIndex()) - return false; - const Expr *E = Value.Base.dyn_cast(); - return E && !isa(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(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(); @@ -1991,6 +1917,33 @@ CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc, QualType Type, return true; } +static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) { + return LVal.Base.dyn_cast(); +} + +static bool IsLiteralLValue(const LValue &Value) { + if (Value.getLValueCallIndex()) + return false; + const Expr *E = Value.Base.dyn_cast(); + return E && !isa(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(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::VisitBuiltinCallExpr(const CallExpr *E, 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::VisitBuiltinCallExpr(const CallExpr *E, } } +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, diff --git a/test/CodeGen/builtin-memfns.c b/test/CodeGen/builtin-memfns.c index 4862677453..d93a5aadae 100644 --- a/test/CodeGen/builtin-memfns.c +++ b/test/CodeGen/builtin-memfns.c @@ -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); -} - diff --git a/test/SemaCXX/constexpr-string.cpp b/test/SemaCXX/constexpr-string.cpp index 1145a2081c..2ed35fcc2b 100644 --- a/test/SemaCXX/constexpr-string.cpp +++ b/test/SemaCXX/constexpr-string.cpp @@ -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 - 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@-1 2{{overlapping memory regions}} - // expected-note@-2 {{size to copy (1) is not a multiple of size of element type 'int'}} - // expected-note@-3 {{source is not a contiguous array of at least 2 elements of type 'int'}} - // expected-note@-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@-1 {{size to copy (1) is not a multiple of size of element type 'int'}} - // expected-note@-2 {{source is not a contiguous array of at least 2 elements of type 'int'}} - // expected-note@-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@-1 2{{overlapping memory regions}} - // expected-note-re@-2 {{source is not a contiguous array of at least 2 elements of type '{{wchar_t|int}}'}} - // expected-note-re@-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@-1 {{source is not a contiguous array of at least 2 elements of type '{{wchar_t|int}}'}} - // expected-note-re@-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}} -} -- 2.40.0