From 967eeb109bedc4ae606fdf6ad6eca58ffbac6739 Mon Sep 17 00:00:00 2001 From: David Tenty Date: Thu, 20 Feb 2020 14:22:16 -0500 Subject: [PATCH] [AIX] Pack BasicBlockBits Summary: D51664 introduces a new structure BasicBlockBits which it expects to be packed a certain way. This change is very similar to D60164, and we apply the same fix: "On AIX, the canonical layout of bit-fields would cause these ... to span four bytes. Applying the pack pragma for compilers that employ the AIX canonical layout allows these ... to fit within the expected two bytes. In the future, the pragma would also likely need to be applied when building with Clang on AIX." Reviewers: jasonliu, hubert.reinterpretcast, sfertile, xingxue Reviewed By: sfertile Subscribers: llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D74911 --- llvm/include/llvm/IR/BasicBlock.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/llvm/include/llvm/IR/BasicBlock.h b/llvm/include/llvm/IR/BasicBlock.h index f04fbd23e964d..4a3c649c7af26 100644 --- a/llvm/include/llvm/IR/BasicBlock.h +++ b/llvm/include/llvm/IR/BasicBlock.h @@ -461,11 +461,26 @@ class BasicBlock final : public Value, // Basic blocks are data objects also void validateInstrOrdering() const; private: +#if defined(_AIX) && (!defined(__GNUC__) || defined(__ibmxl__)) +// Except for GCC; by default, AIX compilers store bit-fields in 4-byte words +// and give the `pack` pragma push semantics. +#define BEGIN_TWO_BYTE_PACK() _Pragma("pack(2)") +#define END_TWO_BYTE_PACK() _Pragma("pack(pop)") +#else +#define BEGIN_TWO_BYTE_PACK() +#define END_TWO_BYTE_PACK() +#endif + + BEGIN_TWO_BYTE_PACK() /// Bitfield to help interpret the bits in Value::SubclassData. struct BasicBlockBits { unsigned short BlockAddressRefCount : 15; unsigned short InstrOrderValid : 1; }; + END_TWO_BYTE_PACK() + +#undef BEGIN_TWO_BYTE_PACK +#undef END_TWO_BYTE_PACK /// Safely reinterpret the subclass data bits to a more useful form. BasicBlockBits getBasicBlockBits() const {