https://github.com/pranavk created https://github.com/llvm/llvm-project/pull/120670
We incorrectly return CXX records in AVX registers when they should be returned in memory. This is violation of x86-64 psABI. Detailed discussion is here: https://groups.google.com/g/x86-64-abi/c/BjOOyihHuqg/m/KurXdUcWAgAJ >From 573cb2685f5ea060eff3d374f58ff04426c1f3d4 Mon Sep 17 00:00:00 2001 From: Pranav Kant <p...@google.com> Date: Fri, 20 Dec 2024 02:17:23 +0000 Subject: [PATCH] [clang] Return larger CXX records in memory We incorrectly return CXX records in AVX registers when they should be returned in memory. This is violation of x86-64 psABI. Detailed discussion is here: https://groups.google.com/g/x86-64-abi/c/BjOOyihHuqg/m/KurXdUcWAgAJ --- clang/include/clang/Basic/LangOptions.h | 1 + clang/lib/CodeGen/Targets/X86.cpp | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+) diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h index 949c8f5d448bcf..0dd644eba559b9 100644 --- a/clang/include/clang/Basic/LangOptions.h +++ b/clang/include/clang/Basic/LangOptions.h @@ -245,6 +245,7 @@ class LangOptionsBase { /// construction vtable because it hasn't added 'type' as a substitution. /// - Skip mangling enclosing class templates of member-like friend /// function templates. + /// - Incorrectly return C++ records in AVX registers. Ver19, /// Conform to the underlying platform's C and C++ ABIs as closely diff --git a/clang/lib/CodeGen/Targets/X86.cpp b/clang/lib/CodeGen/Targets/X86.cpp index 7f73bf2a65266e..70d812057d0b01 100644 --- a/clang/lib/CodeGen/Targets/X86.cpp +++ b/clang/lib/CodeGen/Targets/X86.cpp @@ -1334,6 +1334,20 @@ class X86_64ABIInfo : public ABIInfo { return T.isOSLinux() || T.isOSNetBSD(); } + bool returnCXXRecordGreaterThan128InMem(unsigned Size, unsigned TypeSize, + unsigned NativeSize) const { + // Clang <= 19.0 did not do this. + if (getContext().getLangOpts().getClangABICompat() <= + LangOptions::ClangABI::Ver19) + return false; + + // The only case a 256(or 512)-bit wide vector could be used to return + // is when CXX record contains a single 256(or 512)-bit element. + if (Size > 128 && (Size != TypeSize || Size > NativeSize)) + return true; + return false; + } + X86AVXABILevel AVXLevel; // Some ABIs (e.g. X32 ABI and Native Client OS) use 32 bit pointers on // 64-bit hardware. @@ -2067,6 +2081,10 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase, Class &Lo, classify(I.getType(), Offset, FieldLo, FieldHi, isNamedArg); Lo = merge(Lo, FieldLo); Hi = merge(Hi, FieldHi); + if (returnCXXRecordGreaterThan128InMem( + Size, getContext().getTypeSize(I.getType()), + getNativeVectorSizeForAVXABI(AVXLevel))) + Lo = Memory; if (Lo == Memory || Hi == Memory) { postMerge(Size, Lo, Hi); return; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
