[clang] [WIP][libc++] Add builtin to clear padding bytes (prework for P0528R3) (PR #75371)
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Wed Dec 13 11:41:26 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Hui (huixie90)
<details>
<summary>Changes</summary>
---
Patch is 23.59 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/75371.diff
6 Files Affected:
- (modified) clang/include/clang/Basic/Builtins.def (+1)
- (modified) clang/lib/CodeGen/CGBuiltin.cpp (+137)
- (modified) clang/lib/Sema/SemaChecking.cpp (+20)
- (added) clang/test/CodeGenCXX/builtin-zero-non-value-bits-codegen.cpp (+112)
- (added) clang/test/CodeGenCXX/builtin-zero-non-value-bits.cpp (+359)
- (added) clang/test/SemaCXX/builtin-zero-non-value-bits.cpp (+15)
``````````diff
diff --git a/clang/include/clang/Basic/Builtins.def b/clang/include/clang/Basic/Builtins.def
index ec39e926889b93..ba944a6f04fdc0 100644
--- a/clang/include/clang/Basic/Builtins.def
+++ b/clang/include/clang/Basic/Builtins.def
@@ -633,6 +633,7 @@ BUILTIN(__builtin_vsscanf, "icC*RcC*Ra", "FS:1:")
BUILTIN(__builtin_thread_pointer, "v*", "nc")
BUILTIN(__builtin_launder, "v*v*", "ntE")
LANGBUILTIN(__builtin_is_constant_evaluated, "b", "nE", CXX_LANG)
+LANGBUILTIN(__builtin_zero_non_value_bits, "v.", "n", CXX_LANG)
// GCC exception builtins
BUILTIN(__builtin_eh_return, "vzv*", "r") // FIXME: Takes intptr_t, not size_t!
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 65d9862621061d..638af25fb7a41e 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -63,6 +63,10 @@
#include <optional>
#include <sstream>
+
+
+#include <iostream>
+
using namespace clang;
using namespace CodeGen;
using namespace llvm;
@@ -2456,6 +2460,132 @@ static RValue EmitHipStdParUnsupportedBuiltin(CodeGenFunction *CGF,
return RValue::get(CGF->Builder.CreateCall(UBF, Args));
}
+template <class T>
+void RecursivelyClearPaddingImpl(CodeGenFunction &CGF, Value *Ptr, QualType Ty, size_t CurrentStartOffset, size_t &RunningOffset, T&& WriteZeroAtOffset);
+
+template <class T>
+void ClearPaddingStruct(CodeGenFunction &CGF, Value *Ptr, QualType Ty, StructType *ST,
+ size_t CurrentStartOffset, size_t &RunningOffset, T&& WriteZeroAtOffset) {
+ std::cerr << "\n struct! " << ST->getName().data() << std::endl;
+ auto SL = CGF.CGM.getModule().getDataLayout().getStructLayout(ST);
+ auto R = cast<CXXRecordDecl>(Ty->getAsRecordDecl());
+ const ASTRecordLayout &ASTLayout = CGF.getContext().getASTRecordLayout(R);
+ for (auto Base : R->bases()) {
+ std::cerr << "\n\n base!" << std::endl;
+ // Zero padding between base elements.
+ auto BaseRecord = cast<CXXRecordDecl>(Base.getType()->getAsRecordDecl());
+ auto Offset = static_cast<size_t>(
+ ASTLayout.getBaseClassOffset(BaseRecord).getQuantity());
+ // Recursively zero out base classes.
+ auto Index = SL->getElementContainingOffset(Offset);
+ Value *Idx = CGF.Builder.getSize(Index);
+ llvm::Type *CurrentBaseType = CGF.ConvertTypeForMem(Base.getType());
+ Value *BaseElement = CGF.Builder.CreateGEP(CurrentBaseType, Ptr, Idx);
+ RecursivelyClearPaddingImpl(CGF, BaseElement, Base.getType(), CurrentStartOffset + Offset, RunningOffset, WriteZeroAtOffset);
+ }
+
+ size_t NumFields = std::distance(R->field_begin(), R->field_end());
+ auto CurrentField = R->field_begin();
+ for (size_t I = 0; I < NumFields; ++I, ++CurrentField) {
+ // Size needs to be in bytes so we can compare it later.
+ auto Offset = ASTLayout.getFieldOffset(I) / 8;
+ auto Index = SL->getElementContainingOffset(Offset);
+ Value *Idx = CGF.Builder.getSize(Index);
+ llvm::Type *CurrentFieldType = CGF.ConvertTypeForMem(CurrentField->getType());
+ Value *Element = CGF.Builder.CreateGEP(CurrentFieldType, Ptr, Idx);
+ RecursivelyClearPaddingImpl(CGF, Element, CurrentField->getType(), CurrentStartOffset + Offset, RunningOffset, WriteZeroAtOffset);
+ }
+}
+
+template <class T>
+void ClearPaddingConstantArray(CodeGenFunction &CGF, Value *Ptr, llvm::Type *Type, ConstantArrayType const *AT,
+ size_t CurrentStartOffset, size_t &RunningOffset, T&& WriteZeroAtOffset) {
+ for (size_t ArrIndex = 0; ArrIndex < AT->getSize().getLimitedValue();
+ ++ArrIndex) {
+
+ QualType ElementQualType = AT->getElementType();
+
+ auto *ElementRecord = ElementQualType->getAsRecordDecl();
+ if(!ElementRecord){
+ std::cerr<< "\n\n null!" << std::endl;
+ }
+ auto ElementAlign =ElementRecord?
+ CGF.getContext().getASTRecordLayout(ElementRecord).getAlignment():
+ CGF.getContext().getTypeAlignInChars(ElementQualType);
+
+ std::cerr<< "\n\n align: " << ElementAlign.getQuantity() << std::endl;
+
+ // Value *Idx = CGF.Builder.getSize(0);
+ // Value *ArrayElement = CGF.Builder.CreateGEP(ElementType, Ptr, Idx);
+
+ Address FieldElementAddr{Ptr, Type, ElementAlign};
+
+ auto Element =
+ CGF.Builder.CreateConstArrayGEP(FieldElementAddr, ArrIndex);
+ auto *ElementType = CGF.ConvertTypeForMem(ElementQualType);
+ auto AllocSize = CGF.CGM.getModule().getDataLayout().getTypeAllocSize(ElementType);
+ std::cerr << "\n\n clearing array index! " << ArrIndex << std::endl;
+ RecursivelyClearPaddingImpl(CGF, Element.getPointer(), ElementQualType, CurrentStartOffset + ArrIndex * AllocSize.getKnownMinValue(), RunningOffset, WriteZeroAtOffset);
+ }
+}
+
+template <class T>
+void RecursivelyClearPaddingImpl(CodeGenFunction &CGF, Value *Ptr, QualType Ty, size_t CurrentStartOffset,
+ size_t& RunningOffset, T&& WriteZeroAtOffset) {
+
+ std::cerr << "\n\n zero padding before current ["<< RunningOffset << ", " << CurrentStartOffset<< ")"<< std::endl;
+ for (; RunningOffset < CurrentStartOffset; ++RunningOffset) {
+ WriteZeroAtOffset(RunningOffset);
+ }
+ auto Type = CGF.ConvertTypeForMem(Ty);
+ auto Size = CGF.CGM.getModule()
+ .getDataLayout()
+ .getTypeSizeInBits(Type)
+ .getKnownMinValue() / 8;
+
+ if (auto *AT = dyn_cast<ConstantArrayType>(Ty)) {
+ ClearPaddingConstantArray(CGF, Ptr, Type, AT, CurrentStartOffset, RunningOffset, WriteZeroAtOffset);
+ }
+ else if (auto *ST = dyn_cast<StructType>(Type)) {
+ ClearPaddingStruct(CGF, Ptr, Ty, ST, CurrentStartOffset, RunningOffset, WriteZeroAtOffset);
+ } else {
+ std::cerr << "\n\n increment running offset from: " << RunningOffset << " to " << RunningOffset + Size << std::endl;
+ RunningOffset += Size;
+ }
+
+}
+
+static void RecursivelyZeroNonValueBits(CodeGenFunction &CGF, Value *Ptr,
+ QualType Ty) {
+ auto *I8Ptr = CGF.Builder.CreateBitCast(Ptr, CGF.Int8PtrTy);
+ auto *Zero = ConstantInt::get(CGF.Int8Ty, 0);
+ auto WriteZeroAtOffset = [&](size_t Offset) {
+ auto *Index = ConstantInt::get(CGF.IntTy, Offset);
+ auto *Element = CGF.Builder.CreateGEP(CGF.Int8Ty, I8Ptr, Index);
+ CGF.Builder.CreateAlignedStore(
+ Zero, Element,
+ CharUnits::One().alignmentAtOffset(CharUnits::fromQuantity(Offset)));
+ };
+
+
+ size_t RunningOffset = 0;
+
+ RecursivelyClearPaddingImpl(CGF, Ptr, Ty, 0, RunningOffset, WriteZeroAtOffset);
+
+ // Clear tail padding
+ auto Type = CGF.ConvertTypeForMem(Ty);
+
+ auto Size = CGF.CGM.getModule()
+ .getDataLayout()
+ .getTypeSizeInBits(Type)
+ .getKnownMinValue() / 8;
+
+ std::cerr << "\n\n zero tail padding ["<< RunningOffset << ", " << Size << ")"<< std::endl;
+ for (; RunningOffset < Size; ++RunningOffset) {
+ WriteZeroAtOffset(RunningOffset);
+ }
+}
+
RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
const CallExpr *E,
ReturnValueSlot ReturnValue) {
@@ -4315,6 +4445,13 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
return RValue::get(Ptr);
}
+ case Builtin::BI__builtin_zero_non_value_bits: {
+ const Expr *Op = E->getArg(0);
+ Value *Address = EmitScalarExpr(Op);
+ auto PointeeTy = Op->getType()->getPointeeType();
+ RecursivelyZeroNonValueBits(*this, Address, PointeeTy);
+ return RValue::get(nullptr);
+ }
case Builtin::BI__sync_fetch_and_add:
case Builtin::BI__sync_fetch_and_sub:
case Builtin::BI__sync_fetch_and_or:
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 77c8334f3ca25d..3470dfca3ed6c7 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -2327,6 +2327,26 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
}
case Builtin::BI__builtin_launder:
return SemaBuiltinLaunder(*this, TheCall);
+ case Builtin::BI__builtin_zero_non_value_bits: {
+ // const Expr *PtrArg = TheCall->getArg(0)->IgnoreParenImpCasts();
+ // const QualType PtrArgType = PtrArg->getType();
+ // if (!PtrArgType->isPointerType() ||
+ // !PtrArgType->getPointeeType()->isRecordType()) {
+ // Diag(PtrArg->getBeginLoc(), diag::err_typecheck_convert_incompatible)
+ // << PtrArgType << "structure pointer" << 1 << 0 << 3 << 1 << PtrArgType
+ // << "structure pointer";
+ // return ExprError();
+ // }
+ // if (PtrArgType->getPointeeType().isConstQualified()) {
+ // Diag(PtrArg->getBeginLoc(), diag::err_typecheck_assign_const)
+ // << TheCall->getSourceRange() << 5 /*ConstUnknown*/;
+ // return ExprError();
+ // }
+ // if (RequireCompleteType(PtrArg->getBeginLoc(), PtrArgType->getPointeeType(),
+ // diag::err_typecheck_decl_incomplete_type))
+ // return ExprError();
+ break;
+ }
case Builtin::BI__sync_fetch_and_add:
case Builtin::BI__sync_fetch_and_add_1:
case Builtin::BI__sync_fetch_and_add_2:
diff --git a/clang/test/CodeGenCXX/builtin-zero-non-value-bits-codegen.cpp b/clang/test/CodeGenCXX/builtin-zero-non-value-bits-codegen.cpp
new file mode 100644
index 00000000000000..8ad1e148ded861
--- /dev/null
+++ b/clang/test/CodeGenCXX/builtin-zero-non-value-bits-codegen.cpp
@@ -0,0 +1,112 @@
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+struct alignas(4) Foo {
+ char a;
+ alignas(2) char b;
+};
+
+struct alignas(4) Bar {
+ char c;
+ alignas(2) char d;
+};
+
+struct alignas(4) Baz : Foo {
+ char e;
+ Bar f;
+};
+
+// Baz structure:
+// "a", PAD_1, "b", PAD_2, "c", PAD_3, PAD_4, PAD_5, "c", PAD_6, "d", PAD_7
+// %struct.Baz = type { %struct.Foo, i8, [3 x i8], %struct.Bar }
+// %struct.Foo = type { i8, i8, i8, i8 }
+// %struct.Bar = type { i8, i8, i8, i8 }
+
+// CHECK-LABEL: define void @_Z7testBazP3Baz(%struct.Baz* %baz)
+// CHECK: [[ADDR:%.*]] = alloca %struct.Baz*
+// CHECK: store %struct.Baz* %baz, %struct.Baz** [[ADDR]]
+// CHECK: [[BAZ:%.*]] = load %struct.Baz*, %struct.Baz** [[ADDR]]
+// CHECK: [[BAZ_RAW_PTR:%.*]] = bitcast %struct.Baz* [[BAZ]] to i8*
+
+// CHECK: [[FOO_BASE:%.*]] = getelementptr inbounds %struct.Baz, %struct.Baz* [[BAZ]], i32 0, i32 0
+// CHECK: [[FOO_RAW_PTR:%.*]] = bitcast %struct.Foo* [[FOO_BASE]] to i8*
+// CHECK: [[PAD_1:%.*]] = getelementptr i8, i8* [[FOO_RAW_PTR]], i32 1
+// CHECK: store i8 0, i8* [[PAD_1]]
+// CHECK: [[PAD_2:%.*]] = getelementptr i8, i8* [[FOO_RAW_PTR]], i32 3
+// CHECK: store i8 0, i8* [[PAD_2]]
+
+// CHECK: [[PAD_3:%.*]] = getelementptr i8, i8* [[BAZ_RAW_PTR]], i32 5
+// CHECK: store i8 0, i8* [[PAD_3]]
+// CHECK: [[PAD_4:%.*]] = getelementptr i8, i8* [[BAZ_RAW_PTR]], i32 6
+// CHECK: store i8 0, i8* [[PAD_4]]
+// CHECK: [[PAD_5:%.*]] = getelementptr i8, i8* [[BAZ_RAW_PTR]], i32 7
+// CHECK: store i8 0, i8* [[PAD_5]]
+
+// CHECK: [[BAR_MEMBER:%.*]] = getelementptr inbounds %struct.Baz, %struct.Baz* [[BAZ]], i32 0, i32 3
+// CHECK: [[BAR_RAW_PTR:%.*]] = bitcast %struct.Bar* [[BAR_MEMBER]] to i8*
+// CHECK: [[PAD_6:%.*]] = getelementptr i8, i8* [[BAR_RAW_PTR]], i32 1
+// CHECK: store i8 0, i8* [[PAD_6]]
+// CHECK: [[PAD_7:%.*]] = getelementptr i8, i8* [[BAR_RAW_PTR]], i32 3
+// CHECK: store i8 0, i8* [[PAD_7]]
+// CHECK: ret void
+void testBaz(Baz *baz) {
+ __builtin_zero_non_value_bits(baz);
+}
+
+struct UnsizedTail {
+ int size;
+ alignas(8) char buf[];
+
+ UnsizedTail(int size) : size(size) {}
+};
+
+// UnsizedTail structure:
+// "size", PAD_1, PAD_2, PAD_3, PAD_4
+// %struct.UnsizedTail = type { i32, [4 x i8], [0 x i8] }
+
+// CHECK-LABEL: define void @_Z15testUnsizedTailP11UnsizedTail(%struct.UnsizedTail* %u)
+// CHECK: [[U_ADDR:%.*]] = alloca %struct.UnsizedTail*
+// CHECK: store %struct.UnsizedTail* %u, %struct.UnsizedTail** [[U_ADDR]]
+// CHECK: [[U:%.*]] = load %struct.UnsizedTail*, %struct.UnsizedTail** [[U_ADDR]]
+// CHECK: [[U_RAW_PTR:%.*]] = bitcast %struct.UnsizedTail* [[U]] to i8*
+// CHECK: [[PAD_1:%.*]] = getelementptr i8, i8* [[U_RAW_PTR]], i32 4
+// CHECK: store i8 0, i8* [[PAD_1]]
+// CHECK: [[PAD_2:%.*]] = getelementptr i8, i8* [[U_RAW_PTR]], i32 5
+// CHECK: store i8 0, i8* [[PAD_2]]
+// CHECK: [[PAD_3:%.*]] = getelementptr i8, i8* [[U_RAW_PTR]], i32 6
+// CHECK: store i8 0, i8* [[PAD_3]]
+// CHECK: [[PAD_4:%.*]] = getelementptr i8, i8* [[U_RAW_PTR]], i32 7
+// CHECK: store i8 0, i8* [[PAD_4]]
+// CHECK: ret void
+void testUnsizedTail(UnsizedTail *u) {
+ __builtin_zero_non_value_bits(u);
+}
+
+struct ArrOfStructsWithPadding {
+ Bar bars[2];
+};
+
+// ArrOfStructsWithPadding structure:
+// "c" (1), PAD_1, "d" (1), PAD_2, "c" (2), PAD_3, "d" (2), PAD_4
+// %struct.ArrOfStructsWithPadding = type { [2 x %struct.Bar] }
+
+// CHECK-LABEL: define void @_Z27testArrOfStructsWithPaddingP23ArrOfStructsWithPadding(%struct.ArrOfStructsWithPadding* %arr)
+// CHECK: [[ARR_ADDR:%.*]] = alloca %struct.ArrOfStructsWithPadding*
+// CHECK: store %struct.ArrOfStructsWithPadding* %arr, %struct.ArrOfStructsWithPadding** [[ARR_ADDR]]
+// CHECK: [[ARR:%.*]] = load %struct.ArrOfStructsWithPadding*, %struct.ArrOfStructsWithPadding** [[ARR_ADDR]]
+// CHECK: [[BARS:%.*]] = getelementptr inbounds %struct.ArrOfStructsWithPadding, %struct.ArrOfStructsWithPadding* [[ARR]], i32 0, i32 0
+// CHECK: [[FIRST:%.*]] = getelementptr inbounds [2 x %struct.Bar], [2 x %struct.Bar]* [[BARS]], i64 0, i64 0
+// CHECK: [[FIRST_RAW_PTR:%.*]] = bitcast %struct.Bar* [[FIRST]] to i8*
+// CHECK: [[PAD_1:%.*]] = getelementptr i8, i8* [[FIRST_RAW_PTR]], i32 1
+// CHECK: store i8 0, i8* [[PAD_1]]
+// CHECK: [[PAD_2:%.*]] = getelementptr i8, i8* %4, i32 3
+// CHECK: store i8 0, i8* [[PAD_2]]
+// CHECK: [[SECOND:%.*]] = getelementptr inbounds [2 x %struct.Bar], [2 x %struct.Bar]* [[BARS]], i64 0, i64 1
+// CHECK: [[SECOND_RAW_PTR:%.*]] = bitcast %struct.Bar* [[SECOND]] to i8*
+// CHECK: [[PAD_3:%.*]] = getelementptr i8, i8* [[SECOND_RAW_PTR]], i32 1
+// CHECK: store i8 0, i8* [[PAD_3]]
+// CHECK: [[PAD_4:%.*]] = getelementptr i8, i8* [[SECOND_RAW_PTR]], i32 3
+// CHECK: store i8 0, i8* [[PAD_4]]
+// CHECK: ret void
+void testArrOfStructsWithPadding(ArrOfStructsWithPadding *arr) {
+ __builtin_zero_non_value_bits(arr);
+}
diff --git a/clang/test/CodeGenCXX/builtin-zero-non-value-bits.cpp b/clang/test/CodeGenCXX/builtin-zero-non-value-bits.cpp
new file mode 100644
index 00000000000000..4373dcbdb720ba
--- /dev/null
+++ b/clang/test/CodeGenCXX/builtin-zero-non-value-bits.cpp
@@ -0,0 +1,359 @@
+// RUN: mkdir -p %t
+// RUN: %clang++ %s -o %t/run
+// RUN: %t/run
+
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+#include <new>
+
+template <class T>
+void print_bytes(const T *object)
+{
+ auto size = sizeof(T);
+ const unsigned char * const bytes = reinterpret_cast<const unsigned char *>(object);
+ size_t i;
+
+ fprintf(stderr, "[ ");
+ for(i = 0; i < size; i++)
+ {
+ fprintf(stderr, "%02x ", bytes[i]);
+ }
+ fprintf(stderr, "]\n");
+}
+
+template <size_t A1, size_t A2, class T>
+struct alignas(A1) BasicWithPadding {
+ T x;
+ alignas(A2) T y;
+};
+
+template <size_t A1, size_t A2, size_t N, class T>
+struct alignas(A1) SpacedArrayMembers {
+ T x[N];
+ alignas(A2) char c;
+ T y[N];
+};
+
+template <size_t A1, size_t A2, class T>
+struct alignas(A1) PaddedPointerMembers {
+ T *x;
+ alignas(A2) T *y;
+};
+
+template <size_t A1, size_t A2, size_t A3, class T>
+struct alignas(A1) ThreeMembers {
+ T x;
+ alignas(A2) T y;
+ alignas(A3) T z;
+};
+
+template <class T>
+struct Normal {
+ T a;
+ T b;
+};
+
+template <class T>
+struct X {
+ T x;
+};
+
+template <class T>
+struct Z {
+ T z;
+};
+
+template <size_t A, class T>
+struct YZ : public Z<T> {
+ alignas(A) T y;
+};
+
+template <size_t A1, size_t A2, class T>
+struct alignas(A1) HasBase : public X<T>, public YZ<A2, T> {
+ T a;
+ alignas(A2) T b;
+};
+
+template <size_t A1, size_t A2, class T>
+void testAllForType(T a, T b, T c, T d) {
+ using B = BasicWithPadding<A1, A2, T>;
+ B basic1;
+ memset(&basic1, 0, sizeof(B));
+ basic1.x = a;
+ basic1.y = b;
+ B basic2;
+ memset(&basic2, 42, sizeof(B));
+ basic2.x = a;
+ basic2.y = b;
+ assert(memcmp(&basic1, &basic2, sizeof(B)) != 0);
+ __builtin_zero_non_value_bits(&basic2);
+ assert(memcmp(&basic1, &basic2, sizeof(B)) == 0);
+ using A = SpacedArrayMembers<A1, A2, 2, T>;
+ A arr1;
+ memset(&arr1, 0, sizeof(A));
+ arr1.x[0] = a;
+ arr1.x[1] = b;
+ arr1.y[0] = c;
+ arr1.y[1] = d;
+ A arr2;
+ memset(&arr2, 42, sizeof(A));
+ arr2.x[0] = a;
+ arr2.x[1] = b;
+ arr2.y[0] = c;
+ arr2.y[1] = d;
+ arr2.c = 0;
+ assert(memcmp(&arr1, &arr2, sizeof(A)) != 0);
+ __builtin_zero_non_value_bits(&arr2);
+ assert(memcmp(&arr1, &arr2, sizeof(A)) == 0);
+
+ using P = PaddedPointerMembers<A1, A2, T>;
+ P ptr1;
+ memset(&ptr1, 0, sizeof(P));
+ ptr1.x = &a;
+ ptr1.y = &b;
+ P ptr2;
+ memset(&ptr2, 42, sizeof(P));
+ ptr2.x = &a;
+ ptr2.y = &b;
+ assert(memcmp(&ptr1, &ptr2, sizeof(P)) != 0);
+ __builtin_zero_non_value_bits(&ptr2);
+ assert(memcmp(&ptr1, &ptr2, sizeof(P)) == 0);
+
+ using Three = ThreeMembers<A1, A2, A2, T>;
+ Three three1;
+ memset(&three1, 0, sizeof(Three));
+ three1.x = a;
+ three1.y = b;
+ three1.z = c;
+ Three three2;
+ memset(&three2, 42, sizeof(Three));
+ three2.x = a;
+ three2.y = b;
+ three2.z = c;
+ __builtin_zero_non_value_bits(&three2);
+ assert(memcmp(&three1, &three2, sizeof(Three)) == 0);
+
+ using N = Normal<T>;
+ N normal1;
+ memset(&normal1, 0, sizeof(N));
+ normal1.a = a;
+ normal1.b = b;
+ N normal2;
+ memset(&normal2, 42, sizeof(N));
+ normal2.a = a;
+ normal2.b = b;
+ __builtin_zero_non_value_bits(&normal2);
+ assert(memcmp(&normal1, &normal2, sizeof(N)) == 0);
+
+ using H = HasBase<A1, A2, T>;
+ H base1;
+ memset(&base1, 0, sizeof(H));
+ base1.a = a;
+ base1.b = b;
+ base1.x = c;
+ base1.y = d;
+ base1.z = a;
+ H base2;
+ memset(&base2, 42, sizeof(H));
+ base2.a = a;
+ base2.b = b;
+ base2.x = c;
+ base2.y = d;
+ base2.z = a;
+ assert(memcmp(&base1, &base2, sizeof(H)) != 0);
+ __builtin_zero_non_value_bits(&base2);
+ unsigned i = 0;
+ assert(memcmp(&base1, &base2, sizeof(H)) == 0);
+}
+
+struct UnsizedTail {
+ int size;
+ alignas(8) char buf[];
+
+ UnsizedTail(int size) : size(size) {}
+};
+
+void otherTests() {
+ const size_t size1 = sizeof(UnsizedTail) + 4;
+ char buff1[size1];
+ char buff2[size1];
+ memset(buff1, 0, size1);
+ memset(buff2, 42, size1);
+ auto *u1 = new (buff1) UnsizedTail(4);
+ u1->buf[0] = 1;
+ u1->buf[1] = 2;
+ u1->buf[2] = 3;
+ u1->buf[3] = 4;
+ auto *u2 = new (buff2) UnsizedTail(4);
+ u2->buf[0] = 1;
+ u2->buf[1] = 2;
+ u2->buf[2] = 3;
+ u2->buf[3] = 4;
+ assert(memcmp(u1, u2, sizeof(UnsizedTail)) != 0);
+ __builtin_zero_non_value_bits(u2);
+ assert(memcmp(u1, u2, sizeof(UnsizedTail)) == 0);
+
+ using B = BasicWithPadding<8, 4, char>;
+ auto *basic1 = new B;
+ memset(basic1, 0, sizeof(B));
+ basic1->x = 1;
+ basic1->y = 2;
+ auto *basic2 = new B;
+ memset(basic2, 42, sizeof(B));
+ basic2->x = 1;
+ basic2->y = 2;
+ assert(memcmp(basic1, basic2, sizeof(B)) != 0);
+ __builtin_zero_non_value_bits(basic2);
+ assert(memcmp(basic1, basic2, sizeof(B)) == 0);
+ delete basic2;
+ delete basic1;
+
+ using B = BasicWithPadding<8, 4, char>;
+ B *basic3 = new B;
+ memset(basic3, 0, sizeof(B));
+ basic3->x = 1;
+ basic3->y = 2;
+ B *basic4 = new B;
+ memset(basic4, 42, sizeof(B));
+ basic4->x = 1;
+ basic4->y = 2;
+ assert(memcmp(basic3, basic4, sizeof(B)) != 0);
+ __builtin_zero_non_value_bits(const_cast<volatile B *>(basic4));
+ assert(memcmp(basic3, basic4, sizeof(B)) == 0);
+ delete basic4;
+ delete basic3;
+}
+
+struct Foo {
+ int x;
+ int y;
+};
+
+typedef float Float4Vec __attribute__((ext_vector_type(4)));
+typedef float Float3Vec __attribute__((ext_vector_type(3)));
+
+struct S1 {
+ int x = 0;
+ char c = 0;
+};
+
+struct S2{
+ [[no_unique_address]] S1 s1;
+ bool b;
+ long double l;
+ bool b2;
+};
+
+struct S3{
+ [[no_unique_address]] S1 s1;
+ bool b;
+};
+
+struct alignas(32) S4 {
+ int i;
+};
+struct B1{
+
+};
+
+struct B2 {
+ int x;
+};
+struct B3{
+ char c;
+};
+
+struct B4{
+ bool b;
+};
+
+struct B5{
+ int x2;
+};
+
+struct D:B1,B2,B3,B4,B5{
+ long double l;
+ bool b2;
+}...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/75371
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