diff options
Diffstat (limited to 'clang/lib/CodeGen')
| -rw-r--r-- | clang/lib/CodeGen/ItaniumCXXABI.cpp | 80 |
1 files changed, 39 insertions, 41 deletions
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp index 27825ab85d6..4b1c1c255af 100644 --- a/clang/lib/CodeGen/ItaniumCXXABI.cpp +++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp @@ -1393,25 +1393,7 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF, } // Test whether the variable has completed initialization. - llvm::Value *isInitialized; - - // ARM C++ ABI 3.2.3.1: - // To support the potential use of initialization guard variables - // as semaphores that are the target of ARM SWP and LDREX/STREX - // synchronizing instructions we define a static initialization - // guard variable to be a 4-byte aligned, 4- byte word with the - // following inline access protocol. - // #define INITIALIZED 1 - // if ((obj_guard & INITIALIZED) != INITIALIZED) { - // if (__cxa_guard_acquire(&obj_guard)) - // ... - // } - if (UseARMGuardVarABI && !useInt8GuardVariable) { - llvm::Value *V = Builder.CreateLoad(guard); - llvm::Value *Test1 = llvm::ConstantInt::get(guardTy, 1); - V = Builder.CreateAnd(V, Test1); - isInitialized = Builder.CreateIsNull(V, "guard.uninitialized"); - + // // Itanium C++ ABI 3.3.2: // The following is pseudo-code showing how these functions can be used: // if (obj_guard.first_byte == 0) { @@ -1427,29 +1409,45 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF, // } // } - // ARM64 C++ ABI 3.2.2: - // This ABI instead only specifies the value bit 0 of the static guard - // variable; all other bits are platform defined. Bit 0 shall be 0 when the - // variable is not initialized and 1 when it is. - // FIXME: Reading one bit is no more efficient than reading one byte so - // the codegen is same as generic Itanium ABI. - } else { - // Load the first byte of the guard variable. - llvm::LoadInst *LI = + // Load the first byte of the guard variable. + llvm::LoadInst *LI = Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy)); - LI->setAlignment(1); - - // Itanium ABI: - // An implementation supporting thread-safety on multiprocessor - // systems must also guarantee that references to the initialized - // object do not occur before the load of the initialization flag. - // - // In LLVM, we do this by marking the load Acquire. - if (threadsafe) - LI->setAtomic(llvm::Acquire); - - isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized"); - } + LI->setAlignment(1); + + // Itanium ABI: + // An implementation supporting thread-safety on multiprocessor + // systems must also guarantee that references to the initialized + // object do not occur before the load of the initialization flag. + // + // In LLVM, we do this by marking the load Acquire. + if (threadsafe) + LI->setAtomic(llvm::Acquire); + + // For ARM, we should only check the first bit, rather than the entire byte: + // + // ARM C++ ABI 3.2.3.1: + // To support the potential use of initialization guard variables + // as semaphores that are the target of ARM SWP and LDREX/STREX + // synchronizing instructions we define a static initialization + // guard variable to be a 4-byte aligned, 4-byte word with the + // following inline access protocol. + // #define INITIALIZED 1 + // if ((obj_guard & INITIALIZED) != INITIALIZED) { + // if (__cxa_guard_acquire(&obj_guard)) + // ... + // } + // + // and similarly for ARM64: + // + // ARM64 C++ ABI 3.2.2: + // This ABI instead only specifies the value bit 0 of the static guard + // variable; all other bits are platform defined. Bit 0 shall be 0 when the + // variable is not initialized and 1 when it is. + llvm::Value *V = + (UseARMGuardVarABI && !useInt8GuardVariable) + ? Builder.CreateAnd(LI, llvm::ConstantInt::get(CGM.Int8Ty, 1)) + : LI; + llvm::Value *isInitialized = Builder.CreateIsNull(V, "guard.uninitialized"); llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check"); llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end"); |
