https://github.com/Michael137 created https://github.com/llvm/llvm-project/pull/93809
This is the outcome of the discussions we had in https://discourse.llvm.org/t/rfc-lldb-handling-no-unique-address-in-lldb/77483 To summarize, LLDB creates AST nodes by parsing debug-info and hands those off to Clang for codegen. There are certain Clang attributes that affect structure layout which are not encoded in DWARF, one of which is `[[no_unique_address]]`. But the affects of such attributes *is* encoded in DWARF in terms of member offsets and sizes. So some of the correctness checks that the `RecordLayoutBuilder` performs aren't really necessary for layouts provided by LLDB since we know that the offsets we get from DWARF are correct (modulo corrupt DWARF). Hence this patch guards those asserts behind the `DebuggerSupport` flag. This unblocks the libc++ `compressed_pair` refactor in https://github.com/llvm/llvm-project/issues/93069 >From 91276f5b2dc05032a285b465c0c8a69541bb25c4 Mon Sep 17 00:00:00 2001 From: Michael Buch <michaelbuc...@gmail.com> Date: Thu, 2 May 2024 09:05:01 +0100 Subject: [PATCH] [clang][lldb] Don't assert structure layout correctness for layouts provided by LLDB This is the outcome of the discussions we had in https://discourse.llvm.org/t/rfc-lldb-handling-no-unique-address-in-lldb/77483 To summarize, LLDB creates AST nodes by parsing debug-info and hands those off to Clang for codegen. There are certain Clang attributes that affect structure layout which are not encoded in DWARF, one of which is `[[no_unique_address]]`. But the affects of such attributes *is* encoded in DWARF in terms of member offsets and sizes. So some of the correctness checks that the `RecordLayoutBuilder` performs aren't really necessary for layouts provided by LLDB since we know that the offsets we get from DWARF are correct (modulo corrupt DWARF). Hence this patch guards those asserts behind the `DebuggerSupport` flag. --- clang/lib/CodeGen/CGRecordLayoutBuilder.cpp | 18 ++++--- .../API/lang/cpp/no_unique_address/Makefile | 3 ++ .../no_unique_address/TestNoUniqueAddress.py | 50 +++++++++++++++++++ .../API/lang/cpp/no_unique_address/main.cpp | 35 +++++++++++++ 4 files changed, 100 insertions(+), 6 deletions(-) create mode 100644 lldb/test/API/lang/cpp/no_unique_address/Makefile create mode 100644 lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py create mode 100644 lldb/test/API/lang/cpp/no_unique_address/main.cpp diff --git a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp index 5169be204c14d..32fb032214e28 100644 --- a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp +++ b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp @@ -950,6 +950,9 @@ void CGRecordLowering::calculateZeroInit() { // Verify accumulateBitfields computed the correct storage representations. void CGRecordLowering::checkBitfieldClipping(bool IsNonVirtualBaseType) const { #ifndef NDEBUG + if (Context.getLangOpts().DebuggerSupport) + return; + auto ScissorOffset = calculateTailClippingOffset(IsNonVirtualBaseType); auto Tail = CharUnits::Zero(); for (const auto &M : Members) { @@ -1008,7 +1011,8 @@ void CGRecordLowering::insertPadding() { if (!Member->Data) continue; CharUnits Offset = Member->Offset; - assert(Offset >= Size); + if (!Context.getLangOpts().DebuggerSupport) + assert(Offset >= Size); // Insert padding if we need to. if (Offset != Size.alignTo(Packed ? CharUnits::One() : getAlignment(Member->Data))) @@ -1138,8 +1142,9 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) { const ASTRecordLayout &Layout = getContext().getASTRecordLayout(D); uint64_t TypeSizeInBits = getContext().toBits(Layout.getSize()); - assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) && - "Type size mismatch!"); + if (!Context.getLangOpts().DebuggerSupport) + assert(TypeSizeInBits == getDataLayout().getTypeAllocSizeInBits(Ty) && + "Type size mismatch!"); if (BaseTy) { CharUnits NonVirtualSize = Layout.getNonVirtualSize(); @@ -1147,9 +1152,10 @@ CodeGenTypes::ComputeRecordLayout(const RecordDecl *D, llvm::StructType *Ty) { uint64_t AlignedNonVirtualTypeSizeInBits = getContext().toBits(NonVirtualSize); - assert(AlignedNonVirtualTypeSizeInBits == - getDataLayout().getTypeAllocSizeInBits(BaseTy) && - "Type size mismatch!"); + if (!Context.getLangOpts().DebuggerSupport) + assert(AlignedNonVirtualTypeSizeInBits == + getDataLayout().getTypeAllocSizeInBits(BaseTy) && + "Type size mismatch!"); } // Verify that the LLVM and AST field offsets agree. diff --git a/lldb/test/API/lang/cpp/no_unique_address/Makefile b/lldb/test/API/lang/cpp/no_unique_address/Makefile new file mode 100644 index 0000000000000..99998b20bcb05 --- /dev/null +++ b/lldb/test/API/lang/cpp/no_unique_address/Makefile @@ -0,0 +1,3 @@ +CXX_SOURCES := main.cpp + +include Makefile.rules diff --git a/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py b/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py new file mode 100644 index 0000000000000..373bcb9062cde --- /dev/null +++ b/lldb/test/API/lang/cpp/no_unique_address/TestNoUniqueAddress.py @@ -0,0 +1,50 @@ +""" +Test that LLDB correctly handles fields +marked with [[no_unique_address]]. +""" + +import lldb +from lldbsuite.test.decorators import * +from lldbsuite.test.lldbtest import * +from lldbsuite.test import lldbutil + +class NoUniqueAddressTestCase(TestBase): + def test(self): + self.build() + lldbutil.run_to_source_breakpoint( + self, "return 0", lldb.SBFileSpec("main.cpp", False) + ) + + # Qualified/unqualified lookup to templates in namespace + self.expect_expr("b1", result_type="basic::Foo", result_children=[ValueCheck( + name="a", type="Empty" + )]) + + self.expect_expr("b2", result_type="bases::Foo", result_children=[ + ValueCheck(type="bases::B", children=[ + ValueCheck(name="x", type="Empty") + ]), + ValueCheck(type="bases::A", children=[ + ValueCheck(name="c", type="long", value="1"), + ValueCheck(name="d", type="long", value="2") + ]), + ValueCheck(type="bases::C", children=[ + ValueCheck(name="x", type="Empty") + ]), + ]) + self.expect_expr("b3", result_type="bases::Bar", result_children=[ + ValueCheck(type="bases::B", children=[ + ValueCheck(name="x", type="Empty") + ]), + ValueCheck(type="bases::C", children=[ + ValueCheck(name="x", type="Empty") + ]), + ValueCheck(type="bases::A", children=[ + ValueCheck(name="c", type="long", value="5"), + ValueCheck(name="d", type="long", value="6") + ]), + ]) + + self.expect("frame var b1") + self.expect("frame var b2") + self.expect("frame var b3") diff --git a/lldb/test/API/lang/cpp/no_unique_address/main.cpp b/lldb/test/API/lang/cpp/no_unique_address/main.cpp new file mode 100644 index 0000000000000..424fa90859cea --- /dev/null +++ b/lldb/test/API/lang/cpp/no_unique_address/main.cpp @@ -0,0 +1,35 @@ +struct Empty {}; + +namespace basic { +struct Foo { + [[no_unique_address]] Empty a; +}; +} // namespace basic + +namespace bases { +struct A { + long c, d; +}; + +struct B { + [[no_unique_address]] Empty x; +}; + +struct C { + [[no_unique_address]] Empty x; +}; + +struct Foo : B, A, C {}; +struct Bar : B, C, A {}; +} // namespace bases + +int main() { + basic::Foo b1; + bases::Foo b2; + bases::Bar b3; + b2.c = 1; + b2.d = 2; + b3.c = 5; + b3.d = 6; + return 0; +} _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
