r360404 - Assume `__cxa_allocate_exception` returns an under-aligned memory on
Akira Hatanaka via cfe-commits
cfe-commits at lists.llvm.org
Thu May 9 19:16:37 PDT 2019
Author: ahatanak
Date: Thu May 9 19:16:37 2019
New Revision: 360404
URL: http://llvm.org/viewvc/llvm-project?rev=360404&view=rev
Log:
Assume `__cxa_allocate_exception` returns an under-aligned memory on
Darwin if the version of libc++abi isn't new enough to include the fix
in r319123
This patch resurrects r264998, which was committed to work around a bug
in libc++abi that was causing _cxa_allocate_exception to return a memory
that wasn't double-word aligned.
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20160328/154332.html
In addition, this patch makes clang issue a warning if the type of the
thrown object requires an alignment that is larger than the minimum
guaranteed by the target C++ runtime.
rdar://problem/49864414
Differential Revision: https://reviews.llvm.org/D61667
Added:
cfe/trunk/test/SemaCXX/warn-overaligned-type-thrown.cpp
Modified:
cfe/trunk/include/clang/AST/ASTContext.h
cfe/trunk/include/clang/Basic/DiagnosticGroups.td
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/include/clang/Basic/TargetInfo.h
cfe/trunk/lib/Basic/Targets/OSTargets.h
cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
cfe/trunk/lib/Sema/SemaExprCXX.cpp
cfe/trunk/test/CodeGenCXX/eh.cpp
Modified: cfe/trunk/include/clang/AST/ASTContext.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/ASTContext.h?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/ASTContext.h (original)
+++ cfe/trunk/include/clang/AST/ASTContext.h Thu May 9 19:16:37 2019
@@ -2166,6 +2166,13 @@ public:
/// pointers and large arrays get extra alignment.
CharUnits getDeclAlign(const Decl *D, bool ForAlignof = false) const;
+ /// Return the alignment (in bytes) of the thrown exception object. This is
+ /// only meaningful for targets that allocate C++ exceptions in a system
+ /// runtime, such as those using the Itanium C++ ABI.
+ CharUnits getExnObjectAlignment() const {
+ return toCharUnitsFromBits(Target->getExnObjectAlignment());
+ }
+
/// Get or compute information about the layout of the specified
/// record (struct/union/class) \p D, which indicates its size and field
/// position information.
Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Thu May 9 19:16:37 2019
@@ -408,6 +408,7 @@ def ObjCMultipleMethodNames : DiagGroup<
def ObjCFlexibleArray : DiagGroup<"objc-flexible-array">;
def ObjCBoxing : DiagGroup<"objc-boxing">;
def OpenCLUnsupportedRGBA: DiagGroup<"opencl-unsupported-rgba">;
+def UnderalignedExceptionObject : DiagGroup<"underaligned-exception-object">;
def DeprecatedObjCIsaUsage : DiagGroup<"deprecated-objc-isa-usage">;
def ExplicitInitializeCall : DiagGroup<"explicit-initialize-call">;
def Packed : DiagGroup<"packed">;
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Thu May 9 19:16:37 2019
@@ -6576,6 +6576,12 @@ def err_throw_incomplete : Error<
"cannot throw object of incomplete type %0">;
def err_throw_incomplete_ptr : Error<
"cannot throw pointer to object of incomplete type %0">;
+def warn_throw_underaligned_obj : Warning<
+ "underaligned exception object thrown">,
+ InGroup<UnderalignedExceptionObject>;
+def note_throw_underaligned_obj : Note<
+ "required alignment of type %0 (%1 bytes) is larger than the supported "
+ "alignment of C++ exception objects on this target (%2 bytes)">;
def err_return_in_constructor_handler : Error<
"return in the catch of a function try block of a constructor is illegal">;
def warn_cdtor_function_try_handler_mem_expr : Warning<
Modified: cfe/trunk/include/clang/Basic/TargetInfo.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/TargetInfo.h?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/TargetInfo.h (original)
+++ cfe/trunk/include/clang/Basic/TargetInfo.h Thu May 9 19:16:37 2019
@@ -637,6 +637,21 @@ public:
/// types for the given target.
unsigned getSimdDefaultAlign() const { return SimdDefaultAlign; }
+ /// Return the alignment (in bits) of the thrown exception object. This is
+ /// only meaningful for targets that allocate C++ exceptions in a system
+ /// runtime, such as those using the Itanium C++ ABI.
+ virtual unsigned getExnObjectAlignment() const {
+ // Itanium says that an _Unwind_Exception has to be "double-word"
+ // aligned (and thus the end of it is also so-aligned), meaning 16
+ // bytes. Of course, that was written for the actual Itanium,
+ // which is a 64-bit platform. Classically, the ABI doesn't really
+ // specify the alignment on other platforms, but in practice
+ // libUnwind declares the struct with __attribute__((aligned)), so
+ // we assume that alignment here. (It's generally 16 bytes, but
+ // some targets overwrite it.)
+ return getDefaultAlignForAttributeAligned();
+ }
+
/// Return the size of intmax_t and uintmax_t for this target, in bits.
unsigned getIntMaxTWidth() const {
return getTypeWidth(IntMaxType);
Modified: cfe/trunk/lib/Basic/Targets/OSTargets.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Targets/OSTargets.h?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/lib/Basic/Targets/OSTargets.h (original)
+++ cfe/trunk/lib/Basic/Targets/OSTargets.h Thu May 9 19:16:37 2019
@@ -133,6 +133,37 @@ public:
/// attribute on declarations that can be dynamically replaced.
bool hasProtectedVisibility() const override { return false; }
+ unsigned getExnObjectAlignment() const override {
+ // Older versions of libc++abi guarantee an alignment of only 8-bytes for
+ // exception objects because of a bug in __cxa_exception that was
+ // eventually fixed in r319123.
+ llvm::VersionTuple MinVersion;
+ const llvm::Triple &T = this->getTriple();
+
+ // Compute the earliest OS versions that have the fix to libc++abi.
+ switch (T.getOS()) {
+ case llvm::Triple::Darwin:
+ case llvm::Triple::MacOSX: // Earliest supporting version is 10.14.
+ MinVersion = llvm::VersionTuple(10U, 14U);
+ break;
+ case llvm::Triple::IOS:
+ case llvm::Triple::TvOS: // Earliest supporting version is 12.0.0.
+ MinVersion = llvm::VersionTuple(12U);
+ break;
+ case llvm::Triple::WatchOS: // Earliest supporting version is 5.0.0.
+ MinVersion = llvm::VersionTuple(5U);
+ break;
+ default:
+ llvm_unreachable("Unexpected OS");
+ }
+
+ unsigned Major, Minor, Micro;
+ T.getOSVersion(Major, Minor, Micro);
+ if (llvm::VersionTuple(Major, Minor, Micro) < MinVersion)
+ return 64;
+ return OSTargetInfo<Target>::getExnObjectAlignment();
+ }
+
TargetInfo::IntType getLeastIntTypeByWidth(unsigned BitWidth,
bool IsSigned) const final {
// Darwin uses `long long` for `int_least64_t` and `int_fast64_t`.
Modified: cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp (original)
+++ cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp Thu May 9 19:16:37 2019
@@ -154,19 +154,6 @@ public:
Address Ptr, QualType ElementType,
const CXXDestructorDecl *Dtor) override;
- /// Itanium says that an _Unwind_Exception has to be "double-word"
- /// aligned (and thus the end of it is also so-aligned), meaning 16
- /// bytes. Of course, that was written for the actual Itanium,
- /// which is a 64-bit platform. Classically, the ABI doesn't really
- /// specify the alignment on other platforms, but in practice
- /// libUnwind declares the struct with __attribute__((aligned)), so
- /// we assume that alignment here. (It's generally 16 bytes, but
- /// some targets overwrite it.)
- CharUnits getAlignmentOfExnObject() {
- auto align = CGM.getContext().getTargetDefaultAlignForAttributeAligned();
- return CGM.getContext().toCharUnitsFromBits(align);
- }
-
void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) override;
void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) override;
@@ -1191,7 +1178,7 @@ void ItaniumCXXABI::emitThrow(CodeGenFun
llvm::CallInst *ExceptionPtr = CGF.EmitNounwindRuntimeCall(
AllocExceptionFn, llvm::ConstantInt::get(SizeTy, TypeSize), "exception");
- CharUnits ExnAlign = getAlignmentOfExnObject();
+ CharUnits ExnAlign = CGF.getContext().getExnObjectAlignment();
CGF.EmitAnyExprToExn(E->getSubExpr(), Address(ExceptionPtr, ExnAlign));
// Now throw the exception.
Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExprCXX.cpp?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Thu May 9 19:16:37 2019
@@ -941,6 +941,21 @@ bool Sema::CheckCXXThrowOperand(SourceLo
}
}
+ // Under the Itanium C++ ABI, memory for the exception object is allocated by
+ // the runtime with no ability for the compiler to request additional
+ // alignment. Warn if the exception type requires alignment beyond the minimum
+ // guaranteed by the target C++ runtime.
+ if (Context.getTargetInfo().getCXXABI().isItaniumFamily()) {
+ CharUnits TypeAlign = Context.getTypeAlignInChars(Ty);
+ CharUnits ExnObjAlign = Context.getExnObjectAlignment();
+ if (ExnObjAlign < TypeAlign) {
+ Diag(ThrowLoc, diag::warn_throw_underaligned_obj);
+ Diag(ThrowLoc, diag::note_throw_underaligned_obj)
+ << Ty << (unsigned)TypeAlign.getQuantity()
+ << (unsigned)ExnObjAlign.getQuantity();
+ }
+ }
+
return false;
}
Modified: cfe/trunk/test/CodeGenCXX/eh.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/eh.cpp?rev=360404&r1=360403&r2=360404&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/eh.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/eh.cpp Thu May 9 19:16:37 2019
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -fcxx-exceptions -fexceptions -triple x86_64-apple-darwin -std=c++11 -emit-llvm %s -o - \
-// RUN: | FileCheck %s
+// RUN: %clang_cc1 -fcxx-exceptions -fexceptions -triple x86_64-apple-macosx10.13.99 -std=c++11 -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=UNALIGNED %s
+// RUN: %clang_cc1 -fcxx-exceptions -fexceptions -triple x86_64-apple-macosx10.14 -std=c++11 -emit-llvm -o - %s | FileCheck --check-prefix=CHECK --check-prefix=ALIGNED %s
struct test1_D {
double d;
@@ -13,7 +13,8 @@ void test1() {
// CHECK: [[EXNOBJ:%.*]] = call i8* @__cxa_allocate_exception(i64 8)
// CHECK-NEXT: [[EXN:%.*]] = bitcast i8* [[EXNOBJ]] to [[DSTAR:%[^*]*\*]]
// CHECK-NEXT: [[EXN2:%.*]] = bitcast [[DSTAR]] [[EXN]] to i8*
-// CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 16 [[EXN2]], i8* align 8 bitcast ([[DSTAR]] @d1 to i8*), i64 8, i1 false)
+// UNALIGNED-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[EXN2]], i8* align 8 bitcast ([[DSTAR]] @d1 to i8*), i64 8, i1 false)
+// ALIGNED-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 16 [[EXN2]], i8* align 8 bitcast ([[DSTAR]] @d1 to i8*), i64 8, i1 false)
// CHECK-NEXT: call void @__cxa_throw(i8* [[EXNOBJ]], i8* bitcast ({ i8*, i8* }* @_ZTI7test1_D to i8*), i8* null) [[NR:#[0-9]+]]
// CHECK-NEXT: unreachable
@@ -466,7 +467,8 @@ int foo() {
// CHECK: [[T0:%.*]] = call i8* @__cxa_allocate_exception(i64 16)
// CHECK-NEXT: [[T1:%.*]] = bitcast i8* [[T0]] to %"class.test17::DerivedException"*
// CHECK-NEXT: [[T2:%.*]] = bitcast %"class.test17::DerivedException"* [[T1]] to i8*
- // CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 16 [[T2]], i8 0, i64 16, i1 false)
+ // UNALIGNED-NEXT: call void @llvm.memset.p0i8.i64(i8* align 8 [[T2]], i8 0, i64 16, i1 false)
+ // ALIGNED-NEXT: call void @llvm.memset.p0i8.i64(i8* align 16 [[T2]], i8 0, i64 16, i1 false)
}
}
Added: cfe/trunk/test/SemaCXX/warn-overaligned-type-thrown.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-overaligned-type-thrown.cpp?rev=360404&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-overaligned-type-thrown.cpp (added)
+++ cfe/trunk/test/SemaCXX/warn-overaligned-type-thrown.cpp Thu May 9 19:16:37 2019
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.13.99 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -DUNDERALIGNED %s
+// RUN: %clang_cc1 -triple arm64-apple-ios10 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -DUNDERALIGNED %s
+// RUN: %clang_cc1 -triple arm64-apple-tvos10 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -DUNDERALIGNED %s
+// RUN: %clang_cc1 -triple arm64-apple-watchos4 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -DUNDERALIGNED %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple arm64-apple-ios12 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple arm64-apple-tvos12 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple arm64-apple-watchos5 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple arm-linux-gnueabi -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple aarch64-linux-gnueabi -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple mipsel-linux-gnu -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple mips64el-linux-gnu -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple wasm32-unknown-unknown -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple wasm64-unknown-unknown -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14 -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -Wno-underaligned-exception-object -DNODIAG %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -verify -fsyntax-only -std=c++11 -fcxx-exceptions -fexceptions -DNODIAG %s
+
+struct S0 {
+ S0();
+ int m;
+};
+
+struct Overaligned1 {
+ Overaligned1();
+ int __attribute__((aligned(16))) m;
+};
+
+struct __attribute__((aligned(16))) Overaligned2 {
+ Overaligned2();
+ int m;
+};
+
+struct Overaligned3 {
+ Overaligned3();
+ int __attribute__((aligned(64))) m;
+};
+
+void test0() {
+ throw S0();
+}
+
+void test1() {
+ throw Overaligned1();
+}
+
+void test2() {
+ throw Overaligned2();
+}
+
+void test3() {
+ throw Overaligned3();
+}
+
+#if defined(NODIAG)
+// expected-no-diagnostics
+#elif defined(UNDERALIGNED)
+// expected-warning at -14 {{underaligned exception object thrown}}
+// expected-note at -15 {{(16 bytes) is larger than the supported alignment of C++ exception objects on this target (8 bytes)}}
+// expected-warning at -12 {{underaligned exception object thrown}}
+// expected-note at -13 {{(16 bytes) is larger than the supported alignment of C++ exception objects on this target (8 bytes)}}
+// expected-warning at -10 {{underaligned exception object thrown}}
+// expected-note at -11 {{(64 bytes) is larger than the supported alignment of C++ exception objects on this target (8 bytes)}}
+#else
+// expected-warning at -13 {{underaligned exception object thrown}}
+// expected-note at -14 {{(64 bytes) is larger than the supported alignment of C++ exception objects on this target (16 bytes)}}
+#endif
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