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Added support for constant strings of the form @"this-is-a-string". 

They are replaced with calls to the CoreFoundation function 
CFStringCreateWithBytes() by a portion of the IRForTarget pass.

llvm-svn: 119582
This commit is contained in:
Sean Callanan 2010-11-17 23:00:36 +00:00
parent ac6429fc9a
commit afe16a71f7
2 changed files with 431 additions and 43 deletions
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78
lldb/include/lldb/Expression/IRForTarget.h
View File

@ -17,6 +17,7 @@ namespace llvm {
class CallInst;
class Constant;
class Function;
class GlobalVariable;
class Instruction;
class Module;
class Value;
@ -113,6 +114,54 @@ private:
bool createResultVariable(llvm::Module &M,
llvm::Function &F);
//------------------------------------------------------------------
/// A function-level pass to find Objective-C constant strings and
/// transform them to calls to CFStringCreateWithBytes.
//------------------------------------------------------------------
//------------------------------------------------------------------
/// Rewrite a single Objective-C constant string.
///
/// @param[in] M
/// The module currently being processed.
///
/// @param[in] NSStr
/// The constant NSString to be transformed
///
/// @param[in] CStr
/// The constant C string inside the NSString. This will be
/// passed as the bytes argument to CFStringCreateWithBytes.
///
/// @param[in] FirstEntryInstruction
/// An instruction early in the execution of the function.
/// When this function synthesizes a call to
/// CFStringCreateWithBytes, it places the call before this
/// instruction. The instruction should come before all
/// uses of the NSString.
///
/// @return
/// True on success; false otherwise
//------------------------------------------------------------------
bool rewriteObjCConstString(llvm::Module &M,
llvm::GlobalVariable *NSStr,
llvm::GlobalVariable *CStr,
llvm::Instruction *FirstEntryInstruction);
//------------------------------------------------------------------
/// The top-level pass implementation
///
/// @param[in] M
/// The module currently being processed.
///
/// @param[in] F
/// The function currently being processed.
///
/// @return
/// True on success; false otherwise
//------------------------------------------------------------------
bool rewriteObjCConstStrings(llvm::Module &M,
llvm::Function &F);
//------------------------------------------------------------------
/// A basic block-level pass to find all Objective-C method calls and
/// rewrite them to use sel_registerName instead of statically allocated
@ -327,7 +376,36 @@ private:
std::string m_func_name; ///< The name of the function to translate
lldb_private::ClangExpressionDeclMap *m_decl_map; ///< The DeclMap containing the Decls
llvm::Constant *m_CFStringCreateWithBytes; ///< The address of the function CFStringCreateWithBytes, cast to the appropriate function pointer type
llvm::Constant *m_sel_registerName; ///< The address of the function sel_registerName, cast to the appropriate function pointer type
private:
//------------------------------------------------------------------
/// UnfoldConstant operates on a constant [Old] which has just been
/// replaced with a value [New]. We assume that new_value has
/// been properly placed early in the function, in front of the
/// first instruction in the entry basic block
/// [FirstEntryInstruction].
///
/// UnfoldConstant reads through the uses of Old and replaces Old
/// in those uses with New. Where those uses are constants, the
/// function generates new instructions to compute the result of the
/// new, non-constant expression and places them before
/// FirstEntryInstruction. These instructions replace the constant
/// uses, so UnfoldConstant calls itself recursively for those.
///
/// @param[in] M
/// The module currently being processed.
///
/// @param[in] F
/// The function currently being processed.
///
/// @return
/// True on success; false otherwise
//------------------------------------------------------------------
static bool UnfoldConstant(llvm::Constant *Old,
llvm::Value *New,
llvm::Instruction *FirstEntryInstruction);
};
#endif

388
lldb/source/Expression/IRForTarget.cpp
View File

@ -37,6 +37,7 @@ IRForTarget::IRForTarget(lldb_private::ClangExpressionDeclMap *decl_map,
const char *func_name) :
ModulePass(ID),
m_decl_map(decl_map),
m_CFStringCreateWithBytes(NULL),
m_sel_registerName(NULL),
m_func_name(func_name),
m_resolve_vars(resolve_vars)
@ -256,6 +257,295 @@ IRForTarget::createResultVariable (llvm::Module &llvm_module, llvm::Function &ll
return true;
}
static void DebugUsers(lldb::LogSP &log, Value *V, uint8_t depth)
{
if (!depth)
return;
depth--;
log->Printf(" <Begin %d users>", V->getNumUses());
for (Value::use_iterator ui = V->use_begin(), ue = V->use_end();
ui != ue;
++ui)
{
log->Printf(" <Use %p> %s", *ui, PrintValue(*ui).c_str());
DebugUsers(log, *ui, depth);
}
log->Printf(" <End uses>");
}
bool
IRForTarget::rewriteObjCConstString(llvm::Module &M,
llvm::GlobalVariable *NSStr,
llvm::GlobalVariable *CStr,
Instruction *FirstEntryInstruction)
{
lldb::LogSP log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
const Type *i8_ptr_ty = Type::getInt8PtrTy(M.getContext());
const IntegerType *intptr_ty = Type::getIntNTy(M.getContext(),
(M.getPointerSize() == Module::Pointer64) ? 64 : 32);
const Type *i32_ty = Type::getInt32Ty(M.getContext());
const Type *i8_ty = Type::getInt8Ty(M.getContext());
if (!m_CFStringCreateWithBytes)
{
lldb::addr_t CFStringCreateWithBytes_addr;
static lldb_private::ConstString g_CFStringCreateWithBytes_str ("CFStringCreateWithBytes");
if (!m_decl_map->GetFunctionAddress (g_CFStringCreateWithBytes_str, CFStringCreateWithBytes_addr))
{
if (log)
log->PutCString("Couldn't find CFStringCreateWithBytes in the target");
return false;
}
if (log)
log->Printf("Found CFStringCreateWithBytes at 0x%llx", CFStringCreateWithBytes_addr);
// Build the function type:
//
// CFStringRef CFStringCreateWithBytes (
// CFAllocatorRef alloc,
// const UInt8 *bytes,
// CFIndex numBytes,
// CFStringEncoding encoding,
// Boolean isExternalRepresentation
// );
//
// We make the following substitutions:
//
// CFStringRef -> i8*
// CFAllocatorRef -> i8*
// UInt8 * -> i8*
// CFIndex -> long (i32 or i64, as appropriate; we ask the module for its pointer size for now)
// CFStringEncoding -> i32
// Boolean -> i8
std::vector <const Type *> CFSCWB_arg_types;
CFSCWB_arg_types.push_back(i8_ptr_ty);
CFSCWB_arg_types.push_back(i8_ptr_ty);
CFSCWB_arg_types.push_back(intptr_ty);
CFSCWB_arg_types.push_back(i32_ty);
CFSCWB_arg_types.push_back(i8_ty);
llvm::Type *CFSCWB_ty = FunctionType::get(i8_ptr_ty, CFSCWB_arg_types, false);
// Build the constant containing the pointer to the function
PointerType *CFSCWB_ptr_ty = PointerType::getUnqual(CFSCWB_ty);
Constant *CFSCWB_addr_int = ConstantInt::get(intptr_ty, CFStringCreateWithBytes_addr, false);
m_CFStringCreateWithBytes = ConstantExpr::getIntToPtr(CFSCWB_addr_int, CFSCWB_ptr_ty);
}
ConstantArray *string_array = dyn_cast<ConstantArray>(CStr->getInitializer());
SmallVector <Value*, 5> CFSCWB_arguments;
Constant *alloc_arg = Constant::getNullValue(i8_ptr_ty);
Constant *bytes_arg = ConstantExpr::getBitCast(CStr, i8_ptr_ty);
Constant *numBytes_arg = ConstantInt::get(intptr_ty, string_array->getType()->getNumElements(), false);
Constant *encoding_arg = ConstantInt::get(i32_ty, 0x0600, false); /* 0x0600 is kCFStringEncodingASCII */
Constant *isExternal_arg = ConstantInt::get(i8_ty, 0x0, false); /* 0x0 is false */
CFSCWB_arguments.push_back(alloc_arg);
CFSCWB_arguments.push_back(bytes_arg);
CFSCWB_arguments.push_back(numBytes_arg);
CFSCWB_arguments.push_back(encoding_arg);
CFSCWB_arguments.push_back(isExternal_arg);
CallInst *CFSCWB_call = CallInst::Create(m_CFStringCreateWithBytes,
CFSCWB_arguments.begin(),
CFSCWB_arguments.end(),
"CFStringCreateWithBytes",
FirstEntryInstruction);
Constant *initializer = NSStr->getInitializer();
if (!UnfoldConstant(NSStr, CFSCWB_call, FirstEntryInstruction))
{
if (log)
log->PutCString("Couldn't replace the NSString with the result of the call");
return false;
}
NSStr->eraseFromParent();
return true;
}
bool
IRForTarget::rewriteObjCConstStrings(Module &M,
Function &F)
{
lldb::LogSP log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
ValueSymbolTable& value_symbol_table = M.getValueSymbolTable();
BasicBlock &entry_block(F.getEntryBlock());
Instruction *FirstEntryInstruction(entry_block.getFirstNonPHIOrDbg());
if (!FirstEntryInstruction)
{
if (log)
log->PutCString("Couldn't find first instruction for rewritten Objective-C strings");
return false;
}
for (ValueSymbolTable::iterator vi = value_symbol_table.begin(), ve = value_symbol_table.end();
vi != ve;
++vi)
{
if (strstr(vi->first(), "_unnamed_cfstring_"))
{
Value *nsstring_value = vi->second;
GlobalVariable *nsstring_global = dyn_cast<GlobalVariable>(nsstring_value);
if (!nsstring_global)
{
if (log)
log->PutCString("NSString variable is not a GlobalVariable");
return false;
}
if (!nsstring_global->hasInitializer())
{
if (log)
log->PutCString("NSString variable does not have an initializer");
return false;
}
ConstantStruct *nsstring_struct = dyn_cast<ConstantStruct>(nsstring_global->getInitializer());
if (!nsstring_struct)
{
if (log)
log->PutCString("NSString variable's initializer is not a ConstantStruct");
return false;
}
// We expect the following structure:
//
// struct {
// int *isa;
// int flags;
// char *str;
// long length;
// };
if (nsstring_struct->getNumOperands() != 4)
{
if (log)
log->Printf("NSString variable's initializer structure has an unexpected number of members. Should be 4, is %d", nsstring_struct->getNumOperands());
return false;
}
Constant *nsstring_member = nsstring_struct->getOperand(2);
if (!nsstring_member)
{
if (log)
log->PutCString("NSString initializer's str element was empty");
return false;
}
ConstantExpr *nsstring_expr = dyn_cast<ConstantExpr>(nsstring_member);
if (!nsstring_expr)
{
if (log)
log->PutCString("NSString initializer's str element is not a ConstantExpr");
return false;
}
if (nsstring_expr->getOpcode() != Instruction::GetElementPtr)
{
if (log)
log->Printf("NSString initializer's str element is not a GetElementPtr expression, it's a %s", nsstring_expr->getOpcodeName());
return false;
}
Constant *nsstring_cstr = nsstring_expr->getOperand(0);
GlobalVariable *cstr_global = dyn_cast<GlobalVariable>(nsstring_cstr);
if (!cstr_global)
{
if (log)
log->PutCString("NSString initializer's str element is not a GlobalVariable");
nsstring_cstr->dump();
return false;
}
if (!cstr_global->hasInitializer())
{
if (log)
log->PutCString("NSString initializer's str element does not have an initializer");
return false;
}
ConstantArray *cstr_array = dyn_cast<ConstantArray>(cstr_global->getInitializer());
if (!cstr_array)
{
if (log)
log->PutCString("NSString initializer's str element is not a ConstantArray");
return false;
}
if (!cstr_array->isCString())
{
if (log)
log->PutCString("NSString initializer's str element is not a C string array");
return false;
}
if (log)
log->Printf("Found NSString constant %s, which contains \"%s\"", vi->first(), cstr_array->getAsString().c_str());
if (!rewriteObjCConstString(M, nsstring_global, cstr_global, FirstEntryInstruction))
{
if (log)
log->PutCString("Error rewriting the constant string");
return false;
}
}
}
for (ValueSymbolTable::iterator vi = value_symbol_table.begin(), ve = value_symbol_table.end();
vi != ve;
++vi)
{
if (!strcmp(vi->first(), "__CFConstantStringClassReference"))
{
GlobalVariable *gv = dyn_cast<GlobalVariable>(vi->second);
if (!gv)
{
if (log)
log->PutCString("__CFConstantStringClassReference is not a global variable");
return false;
}
gv->eraseFromParent();
break;
}
}
return true;
}
static bool isObjCSelectorRef(Value *V)
{
GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
@ -366,7 +656,7 @@ IRForTarget::RewriteObjCSelector(Instruction* selector_load,
CallInst *srN_call = CallInst::Create(m_sel_registerName,
srN_arguments.begin(),
srN_arguments.end(),
"srN",
"sel_registerName",
selector_load);
// Replace the load with the call in all users
@ -638,14 +928,14 @@ IRForTarget::MaybeHandleVariable
bool
IRForTarget::MaybeHandleCallArguments(Module &M,
CallInst *C)
CallInst *Old)
{
// lldb::LogSP log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
for (unsigned op_index = 0, num_ops = C->getNumArgOperands();
for (unsigned op_index = 0, num_ops = Old->getNumArgOperands();
op_index < num_ops;
++op_index)
if (!MaybeHandleVariable(M, C->getArgOperand(op_index))) // conservatively believe that this is a store
if (!MaybeHandleVariable(M, Old->getArgOperand(op_index))) // conservatively believe that this is a store
return false;
return true;
@ -813,9 +1103,9 @@ IRForTarget::resolveExternals(Module &M,
static bool isGuardVariableRef(Value *V)
{
Constant *C;
Constant *Old;
if (!(C = dyn_cast<Constant>(V)))
if (!(Old = dyn_cast<Constant>(V)))
return false;
ConstantExpr *CE;
@ -825,10 +1115,10 @@ static bool isGuardVariableRef(Value *V)
if (CE->getOpcode() != Instruction::BitCast)
return false;
C = CE->getOperand(0);
Old = CE->getOperand(0);
}
GlobalVariable *GV = dyn_cast<GlobalVariable>(C);
GlobalVariable *GV = dyn_cast<GlobalVariable>(Old);
if (!GV || !GV->hasName() || !GV->getName().startswith("_ZGV"))
return false;
@ -909,19 +1199,8 @@ IRForTarget::removeGuards(Module &M, BasicBlock &BB)
return true;
}
// UnfoldConstant operates on a constant [C] which has just been replaced with a value
// [new_value]. We assume that new_value has been properly placed early in the function,
// most likely somewhere in front of the first instruction in the entry basic block
// [first_entry_instruction].
//
// UnfoldConstant reads through the uses of C and replaces C in those uses with new_value.
// Where those uses are constants, the function generates new instructions to compute the
// result of the new, non-constant expression and places them before first_entry_instruction.
// These instructions replace the constant uses, so UnfoldConstant calls itself recursively
// for those.
static bool
UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instruction)
bool
IRForTarget::UnfoldConstant(Constant *Old, Value *New, Instruction *FirstEntryInstruction)
{
lldb::LogSP log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
@ -931,8 +1210,8 @@ UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instructi
// We do this because the use list might change, invalidating our iterator.
// Much better to keep a work list ourselves.
for (ui = C->use_begin();
ui != C->use_end();
for (ui = Old->use_begin();
ui != Old->use_end();
++ui)
users.push_back(*ui);
@ -961,12 +1240,12 @@ UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instructi
Value *s = constant_expr->getOperand(0);
if (s == C)
s = new_value;
if (s == Old)
s = New;
BitCastInst *bit_cast(new BitCastInst(s, C->getType(), "", first_entry_instruction));
BitCastInst *bit_cast(new BitCastInst(s, Old->getType(), "", FirstEntryInstruction));
UnfoldConstant(constant_expr, bit_cast, first_entry_instruction);
UnfoldConstant(constant_expr, bit_cast, FirstEntryInstruction);
}
break;
case Instruction::GetElementPtr:
@ -977,8 +1256,8 @@ UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instructi
Value *ptr = constant_expr->getOperand(0);
if (ptr == C)
ptr = new_value;
if (ptr == Old)
ptr = New;
SmallVector<Value*, 16> indices;
@ -991,15 +1270,15 @@ UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instructi
{
Value *operand = constant_expr->getOperand(operand_index);
if (operand == C)
operand = new_value;
if (operand == Old)
operand = New;
indices.push_back(operand);
}
GetElementPtrInst *get_element_ptr(GetElementPtrInst::Create(ptr, indices.begin(), indices.end(), "", first_entry_instruction));
GetElementPtrInst *get_element_ptr(GetElementPtrInst::Create(ptr, indices.begin(), indices.end(), "", FirstEntryInstruction));
UnfoldConstant(constant_expr, get_element_ptr, first_entry_instruction);
UnfoldConstant(constant_expr, get_element_ptr, FirstEntryInstruction);
}
break;
}
@ -1014,7 +1293,7 @@ UnfoldConstant(Constant *C, Value *new_value, Instruction *first_entry_instructi
else
{
// simple fall-through case for non-constants
user->replaceUsesOfWith(C, new_value);
user->replaceUsesOfWith(Old, New);
}
}
@ -1067,9 +1346,9 @@ IRForTarget::replaceVariables(Module &M, Function &F)
log->Printf("Arg: \"%s\"", PrintValue(argument).c_str());
BasicBlock &entry_block(F.getEntryBlock());
Instruction *first_entry_instruction(entry_block.getFirstNonPHIOrDbg());
Instruction *FirstEntryInstruction(entry_block.getFirstNonPHIOrDbg());
if (!first_entry_instruction)
if (!FirstEntryInstruction)
return false;
LLVMContext &context(M.getContext());
@ -1096,11 +1375,11 @@ IRForTarget::replaceVariables(Module &M, Function &F)
offset);
ConstantInt *offset_int(ConstantInt::getSigned(offset_type, offset));
GetElementPtrInst *get_element_ptr = GetElementPtrInst::Create(argument, offset_int, "", first_entry_instruction);
BitCastInst *bit_cast = new BitCastInst(get_element_ptr, value->getType(), "", first_entry_instruction);
GetElementPtrInst *get_element_ptr = GetElementPtrInst::Create(argument, offset_int, "", FirstEntryInstruction);
BitCastInst *bit_cast = new BitCastInst(get_element_ptr, value->getType(), "", FirstEntryInstruction);
if (Constant *constant = dyn_cast<Constant>(value))
UnfoldConstant(constant, bit_cast, first_entry_instruction);
UnfoldConstant(constant, bit_cast, FirstEntryInstruction);
else
value->replaceAllUsesWith(bit_cast);
@ -1138,6 +1417,37 @@ IRForTarget::runOnModule(Module &M)
if (!createResultVariable(M, *function))
return false;
///////////////////////////////////////////////////////////////////////////////
// Fix all Objective-C constant strings to use NSStringWithCString:encoding:
//
if (log)
{
std::string s;
raw_string_ostream oss(s);
M.print(oss, NULL);
oss.flush();
log->Printf("Module after creating the result variable: \n\"%s\"", s.c_str());
}
if (!rewriteObjCConstStrings(M, *function))
return false;
if (log)
{
std::string s;
raw_string_ostream oss(s);
M.print(oss, NULL);
oss.flush();
log->Printf("Module after rewriting Objective-C const strings: \n\"%s\"", s.c_str());
}
//////////////////////////////////
// Run basic-block level passes
//