+++ /dev/null
-//===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the lowering of setjmp and longjmp to use the
-// LLVM invoke and unwind instructions as necessary.
-//
-// Lowering of longjmp is fairly trivial. We replace the call with a
-// call to the LLVM library function "__llvm_sjljeh_throw_longjmp()".
-// This unwinds the stack for us calling all of the destructors for
-// objects allocated on the stack.
-//
-// At a setjmp call, the basic block is split and the setjmp removed.
-// The calls in a function that have a setjmp are converted to invoke
-// where the except part checks to see if it's a longjmp exception and,
-// if so, if it's handled in the function. If it is, then it gets the
-// value returned by the longjmp and goes to where the basic block was
-// split. Invoke instructions are handled in a similar fashion with the
-// original except block being executed if it isn't a longjmp except
-// that is handled by that function.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-// FIXME: This pass doesn't deal with PHI statements just yet. That is,
-// we expect this to occur before SSAification is done. This would seem
-// to make sense, but in general, it might be a good idea to make this
-// pass invokable via the "opt" command at will.
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "lowersetjmp"
-#include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/Intrinsics.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/InstVisitor.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/DepthFirstIterator.h"
-#include "llvm/ADT/Statistic.h"
-#include <map>
-using namespace llvm;
-
-STATISTIC(LongJmpsTransformed, "Number of longjmps transformed");
-STATISTIC(SetJmpsTransformed , "Number of setjmps transformed");
-STATISTIC(CallsTransformed , "Number of calls invokified");
-STATISTIC(InvokesTransformed , "Number of invokes modified");
-
-namespace {
- //===--------------------------------------------------------------------===//
- // LowerSetJmp pass implementation.
- class LowerSetJmp : public ModulePass, public InstVisitor<LowerSetJmp> {
- // LLVM library functions...
- Constant *InitSJMap; // __llvm_sjljeh_init_setjmpmap
- Constant *DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap
- Constant *AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map
- Constant *ThrowLongJmp; // __llvm_sjljeh_throw_longjmp
- Constant *TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception
- Constant *IsLJException; // __llvm_sjljeh_is_longjmp_exception
- Constant *GetLJValue; // __llvm_sjljeh_get_longjmp_value
-
- typedef std::pair<SwitchInst*, CallInst*> SwitchValuePair;
-
- // Keep track of those basic blocks reachable via a depth-first search of
- // the CFG from a setjmp call. We only need to transform those "call" and
- // "invoke" instructions that are reachable from the setjmp call site.
- std::set<BasicBlock*> DFSBlocks;
-
- // The setjmp map is going to hold information about which setjmps
- // were called (each setjmp gets its own number) and with which
- // buffer it was called.
- std::map<Function*, AllocaInst*> SJMap;
-
- // The rethrow basic block map holds the basic block to branch to if
- // the exception isn't handled in the current function and needs to
- // be rethrown.
- std::map<const Function*, BasicBlock*> RethrowBBMap;
-
- // The preliminary basic block map holds a basic block that grabs the
- // exception and determines if it's handled by the current function.
- std::map<const Function*, BasicBlock*> PrelimBBMap;
-
- // The switch/value map holds a switch inst/call inst pair. The
- // switch inst controls which handler (if any) gets called and the
- // value is the value returned to that handler by the call to
- // __llvm_sjljeh_get_longjmp_value.
- std::map<const Function*, SwitchValuePair> SwitchValMap;
-
- // A map of which setjmps we've seen so far in a function.
- std::map<const Function*, unsigned> SetJmpIDMap;
-
- AllocaInst* GetSetJmpMap(Function* Func);
- BasicBlock* GetRethrowBB(Function* Func);
- SwitchValuePair GetSJSwitch(Function* Func, BasicBlock* Rethrow);
-
- void TransformLongJmpCall(CallInst* Inst);
- void TransformSetJmpCall(CallInst* Inst);
-
- bool IsTransformableFunction(StringRef Name);
- public:
- static char ID; // Pass identification, replacement for typeid
- LowerSetJmp() : ModulePass(ID) {
- initializeLowerSetJmpPass(*PassRegistry::getPassRegistry());
- }
-
- void visitCallInst(CallInst& CI);
- void visitInvokeInst(InvokeInst& II);
- void visitReturnInst(ReturnInst& RI);
- void visitUnwindInst(UnwindInst& UI);
-
- bool runOnModule(Module& M);
- bool doInitialization(Module& M);
- };
-} // end anonymous namespace
-
-char LowerSetJmp::ID = 0;
-INITIALIZE_PASS(LowerSetJmp, "lowersetjmp", "Lower Set Jump", false, false)
-
-// run - Run the transformation on the program. We grab the function
-// prototypes for longjmp and setjmp. If they are used in the program,
-// then we can go directly to the places they're at and transform them.
-bool LowerSetJmp::runOnModule(Module& M) {
- bool Changed = false;
-
- // These are what the functions are called.
- Function* SetJmp = M.getFunction("llvm.setjmp");
- Function* LongJmp = M.getFunction("llvm.longjmp");
-
- // This program doesn't have longjmp and setjmp calls.
- if ((!LongJmp || LongJmp->use_empty()) &&
- (!SetJmp || SetJmp->use_empty())) return false;
-
- // Initialize some values and functions we'll need to transform the
- // setjmp/longjmp functions.
- doInitialization(M);
-
- if (SetJmp) {
- for (Value::use_iterator B = SetJmp->use_begin(), E = SetJmp->use_end();
- B != E; ++B) {
- BasicBlock* BB = cast<Instruction>(*B)->getParent();
- for (df_ext_iterator<BasicBlock*> I = df_ext_begin(BB, DFSBlocks),
- E = df_ext_end(BB, DFSBlocks); I != E; ++I)
- /* empty */;
- }
-
- while (!SetJmp->use_empty()) {
- assert(isa<CallInst>(SetJmp->use_back()) &&
- "User of setjmp intrinsic not a call?");
- TransformSetJmpCall(cast<CallInst>(SetJmp->use_back()));
- Changed = true;
- }
- }
-
- if (LongJmp)
- while (!LongJmp->use_empty()) {
- assert(isa<CallInst>(LongJmp->use_back()) &&
- "User of longjmp intrinsic not a call?");
- TransformLongJmpCall(cast<CallInst>(LongJmp->use_back()));
- Changed = true;
- }
-
- // Now go through the affected functions and convert calls and invokes
- // to new invokes...
- for (std::map<Function*, AllocaInst*>::iterator
- B = SJMap.begin(), E = SJMap.end(); B != E; ++B) {
- Function* F = B->first;
- for (Function::iterator BB = F->begin(), BE = F->end(); BB != BE; ++BB)
- for (BasicBlock::iterator IB = BB->begin(), IE = BB->end(); IB != IE; ) {
- visit(*IB++);
- if (IB != BB->end() && IB->getParent() != BB)
- break; // The next instruction got moved to a different block!
- }
- }
-
- DFSBlocks.clear();
- SJMap.clear();
- RethrowBBMap.clear();
- PrelimBBMap.clear();
- SwitchValMap.clear();
- SetJmpIDMap.clear();
-
- return Changed;
-}
-
-// doInitialization - For the lower long/setjmp pass, this ensures that a
-// module contains a declaration for the intrisic functions we are going
-// to call to convert longjmp and setjmp calls.
-//
-// This function is always successful, unless it isn't.
-bool LowerSetJmp::doInitialization(Module& M)
-{
- Type *SBPTy = Type::getInt8PtrTy(M.getContext());
- Type *SBPPTy = PointerType::getUnqual(SBPTy);
-
- // N.B. See llvm/runtime/GCCLibraries/libexception/SJLJ-Exception.h for
- // a description of the following library functions.
-
- // void __llvm_sjljeh_init_setjmpmap(void**)
- InitSJMap = M.getOrInsertFunction("__llvm_sjljeh_init_setjmpmap",
- Type::getVoidTy(M.getContext()),
- SBPPTy, (Type *)0);
- // void __llvm_sjljeh_destroy_setjmpmap(void**)
- DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap",
- Type::getVoidTy(M.getContext()),
- SBPPTy, (Type *)0);
-
- // void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned)
- AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map",
- Type::getVoidTy(M.getContext()),
- SBPPTy, SBPTy,
- Type::getInt32Ty(M.getContext()),
- (Type *)0);
-
- // void __llvm_sjljeh_throw_longjmp(int*, int)
- ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp",
- Type::getVoidTy(M.getContext()), SBPTy,
- Type::getInt32Ty(M.getContext()),
- (Type *)0);
-
- // unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **)
- TryCatchLJ =
- M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception",
- Type::getInt32Ty(M.getContext()), SBPPTy, (Type *)0);
-
- // bool __llvm_sjljeh_is_longjmp_exception()
- IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception",
- Type::getInt1Ty(M.getContext()),
- (Type *)0);
-
- // int __llvm_sjljeh_get_longjmp_value()
- GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value",
- Type::getInt32Ty(M.getContext()),
- (Type *)0);
- return true;
-}
-
-// IsTransformableFunction - Return true if the function name isn't one
-// of the ones we don't want transformed. Currently, don't transform any
-// "llvm.{setjmp,longjmp}" functions and none of the setjmp/longjmp error
-// handling functions (beginning with __llvm_sjljeh_...they don't throw
-// exceptions).
-bool LowerSetJmp::IsTransformableFunction(StringRef Name) {
- return !Name.startswith("__llvm_sjljeh_");
-}
-
-// TransformLongJmpCall - Transform a longjmp call into a call to the
-// internal __llvm_sjljeh_throw_longjmp function. It then takes care of
-// throwing the exception for us.
-void LowerSetJmp::TransformLongJmpCall(CallInst* Inst)
-{
- Type* SBPTy = Type::getInt8PtrTy(Inst->getContext());
-
- // Create the call to "__llvm_sjljeh_throw_longjmp". This takes the
- // same parameters as "longjmp", except that the buffer is cast to a
- // char*. It returns "void", so it doesn't need to replace any of
- // Inst's uses and doesn't get a name.
- CastInst* CI =
- new BitCastInst(Inst->getArgOperand(0), SBPTy, "LJBuf", Inst);
- Value *Args[] = { CI, Inst->getArgOperand(1) };
- CallInst::Create(ThrowLongJmp, Args, "", Inst);
-
- SwitchValuePair& SVP = SwitchValMap[Inst->getParent()->getParent()];
-
- // If the function has a setjmp call in it (they are transformed first)
- // we should branch to the basic block that determines if this longjmp
- // is applicable here. Otherwise, issue an unwind.
- if (SVP.first)
- BranchInst::Create(SVP.first->getParent(), Inst);
- else
- new UnwindInst(Inst->getContext(), Inst);
-
- // Remove all insts after the branch/unwind inst. Go from back to front to
- // avoid replaceAllUsesWith if possible.
- BasicBlock *BB = Inst->getParent();
- Instruction *Removed;
- do {
- Removed = &BB->back();
- // If the removed instructions have any users, replace them now.
- if (!Removed->use_empty())
- Removed->replaceAllUsesWith(UndefValue::get(Removed->getType()));
- Removed->eraseFromParent();
- } while (Removed != Inst);
-
- ++LongJmpsTransformed;
-}
-
-// GetSetJmpMap - Retrieve (create and initialize, if necessary) the
-// setjmp map. This map is going to hold information about which setjmps
-// were called (each setjmp gets its own number) and with which buffer it
-// was called. There can be only one!
-AllocaInst* LowerSetJmp::GetSetJmpMap(Function* Func)
-{
- if (SJMap[Func]) return SJMap[Func];
-
- // Insert the setjmp map initialization before the first instruction in
- // the function.
- Instruction* Inst = Func->getEntryBlock().begin();
- assert(Inst && "Couldn't find even ONE instruction in entry block!");
-
- // Fill in the alloca and call to initialize the SJ map.
- Type *SBPTy =
- Type::getInt8PtrTy(Func->getContext());
- AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst);
- CallInst::Create(InitSJMap, Map, "", Inst);
- return SJMap[Func] = Map;
-}
-
-// GetRethrowBB - Only one rethrow basic block is needed per function.
-// If this is a longjmp exception but not handled in this block, this BB
-// performs the rethrow.
-BasicBlock* LowerSetJmp::GetRethrowBB(Function* Func)
-{
- if (RethrowBBMap[Func]) return RethrowBBMap[Func];
-
- // The basic block we're going to jump to if we need to rethrow the
- // exception.
- BasicBlock* Rethrow =
- BasicBlock::Create(Func->getContext(), "RethrowExcept", Func);
-
- // Fill in the "Rethrow" BB with a call to rethrow the exception. This
- // is the last instruction in the BB since at this point the runtime
- // should exit this function and go to the next function.
- new UnwindInst(Func->getContext(), Rethrow);
- return RethrowBBMap[Func] = Rethrow;
-}
-
-// GetSJSwitch - Return the switch statement that controls which handler
-// (if any) gets called and the value returned to that handler.
-LowerSetJmp::SwitchValuePair LowerSetJmp::GetSJSwitch(Function* Func,
- BasicBlock* Rethrow)
-{
- if (SwitchValMap[Func].first) return SwitchValMap[Func];
-
- BasicBlock* LongJmpPre =
- BasicBlock::Create(Func->getContext(), "LongJmpBlkPre", Func);
-
- // Keep track of the preliminary basic block for some of the other
- // transformations.
- PrelimBBMap[Func] = LongJmpPre;
-
- // Grab the exception.
- CallInst* Cond = CallInst::Create(IsLJException, "IsLJExcept", LongJmpPre);
-
- // The "decision basic block" gets the number associated with the
- // setjmp call returning to switch on and the value returned by
- // longjmp.
- BasicBlock* DecisionBB =
- BasicBlock::Create(Func->getContext(), "LJDecisionBB", Func);
-
- BranchInst::Create(DecisionBB, Rethrow, Cond, LongJmpPre);
-
- // Fill in the "decision" basic block.
- CallInst* LJVal = CallInst::Create(GetLJValue, "LJVal", DecisionBB);
- CallInst* SJNum = CallInst::Create(TryCatchLJ, GetSetJmpMap(Func), "SJNum",
- DecisionBB);
-
- SwitchInst* SI = SwitchInst::Create(SJNum, Rethrow, 0, DecisionBB);
- return SwitchValMap[Func] = SwitchValuePair(SI, LJVal);
-}
-
-// TransformSetJmpCall - The setjmp call is a bit trickier to transform.
-// We're going to convert all setjmp calls to nops. Then all "call" and
-// "invoke" instructions in the function are converted to "invoke" where
-// the "except" branch is used when returning from a longjmp call.
-void LowerSetJmp::TransformSetJmpCall(CallInst* Inst)
-{
- BasicBlock* ABlock = Inst->getParent();
- Function* Func = ABlock->getParent();
-
- // Add this setjmp to the setjmp map.
- Type* SBPTy =
- Type::getInt8PtrTy(Inst->getContext());
- CastInst* BufPtr =
- new BitCastInst(Inst->getArgOperand(0), SBPTy, "SBJmpBuf", Inst);
- Value *Args[] = {
- GetSetJmpMap(Func), BufPtr,
- ConstantInt::get(Type::getInt32Ty(Inst->getContext()), SetJmpIDMap[Func]++)
- };
- CallInst::Create(AddSJToMap, Args, "", Inst);
-
- // We are guaranteed that there are no values live across basic blocks
- // (because we are "not in SSA form" yet), but there can still be values live
- // in basic blocks. Because of this, splitting the setjmp block can cause
- // values above the setjmp to not dominate uses which are after the setjmp
- // call. For all of these occasions, we must spill the value to the stack.
- //
- std::set<Instruction*> InstrsAfterCall;
-
- // The call is probably very close to the end of the basic block, for the
- // common usage pattern of: 'if (setjmp(...))', so keep track of the
- // instructions after the call.
- for (BasicBlock::iterator I = ++BasicBlock::iterator(Inst), E = ABlock->end();
- I != E; ++I)
- InstrsAfterCall.insert(I);
-
- for (BasicBlock::iterator II = ABlock->begin();
- II != BasicBlock::iterator(Inst); ++II)
- // Loop over all of the uses of instruction. If any of them are after the
- // call, "spill" the value to the stack.
- for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
- UI != E; ++UI) {
- User *U = *UI;
- if (cast<Instruction>(U)->getParent() != ABlock ||
- InstrsAfterCall.count(cast<Instruction>(U))) {
- DemoteRegToStack(*II);
- break;
- }
- }
- InstrsAfterCall.clear();
-
- // Change the setjmp call into a branch statement. We'll remove the
- // setjmp call in a little bit. No worries.
- BasicBlock* SetJmpContBlock = ABlock->splitBasicBlock(Inst);
- assert(SetJmpContBlock && "Couldn't split setjmp BB!!");
-
- SetJmpContBlock->setName(ABlock->getName()+"SetJmpCont");
-
- // Add the SetJmpContBlock to the set of blocks reachable from a setjmp.
- DFSBlocks.insert(SetJmpContBlock);
-
- // This PHI node will be in the new block created from the
- // splitBasicBlock call.
- PHINode* PHI = PHINode::Create(Type::getInt32Ty(Inst->getContext()), 2,
- "SetJmpReturn", Inst);
-
- // Coming from a call to setjmp, the return is 0.
- PHI->addIncoming(Constant::getNullValue(Type::getInt32Ty(Inst->getContext())),
- ABlock);
-
- // Add the case for this setjmp's number...
- SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func));
- SVP.first->addCase(ConstantInt::get(Type::getInt32Ty(Inst->getContext()),
- SetJmpIDMap[Func] - 1),
- SetJmpContBlock);
-
- // Value coming from the handling of the exception.
- PHI->addIncoming(SVP.second, SVP.second->getParent());
-
- // Replace all uses of this instruction with the PHI node created by
- // the eradication of setjmp.
- Inst->replaceAllUsesWith(PHI);
- Inst->eraseFromParent();
-
- ++SetJmpsTransformed;
-}
-
-// visitCallInst - This converts all LLVM call instructions into invoke
-// instructions. The except part of the invoke goes to the "LongJmpBlkPre"
-// that grabs the exception and proceeds to determine if it's a longjmp
-// exception or not.
-void LowerSetJmp::visitCallInst(CallInst& CI)
-{
- if (CI.getCalledFunction())
- if (!IsTransformableFunction(CI.getCalledFunction()->getName()) ||
- CI.getCalledFunction()->isIntrinsic()) return;
-
- BasicBlock* OldBB = CI.getParent();
-
- // If not reachable from a setjmp call, don't transform.
- if (!DFSBlocks.count(OldBB)) return;
-
- BasicBlock* NewBB = OldBB->splitBasicBlock(CI);
- assert(NewBB && "Couldn't split BB of \"call\" instruction!!");
- DFSBlocks.insert(NewBB);
- NewBB->setName("Call2Invoke");
-
- Function* Func = OldBB->getParent();
-
- // Construct the new "invoke" instruction.
- TerminatorInst* Term = OldBB->getTerminator();
- CallSite CS(&CI);
- std::vector<Value*> Params(CS.arg_begin(), CS.arg_end());
- InvokeInst* II =
- InvokeInst::Create(CI.getCalledValue(), NewBB, PrelimBBMap[Func],
- Params, CI.getName(), Term);
- II->setCallingConv(CI.getCallingConv());
- II->setAttributes(CI.getAttributes());
-
- // Replace the old call inst with the invoke inst and remove the call.
- CI.replaceAllUsesWith(II);
- CI.eraseFromParent();
-
- // The old terminator is useless now that we have the invoke inst.
- Term->eraseFromParent();
- ++CallsTransformed;
-}
-
-// visitInvokeInst - Converting the "invoke" instruction is fairly
-// straight-forward. The old exception part is replaced by a query asking
-// if this is a longjmp exception. If it is, then it goes to the longjmp
-// exception blocks. Otherwise, control is passed the old exception.
-void LowerSetJmp::visitInvokeInst(InvokeInst& II)
-{
- if (II.getCalledFunction())
- if (!IsTransformableFunction(II.getCalledFunction()->getName()) ||
- II.getCalledFunction()->isIntrinsic()) return;
-
- BasicBlock* BB = II.getParent();
-
- // If not reachable from a setjmp call, don't transform.
- if (!DFSBlocks.count(BB)) return;
-
- BasicBlock* ExceptBB = II.getUnwindDest();
-
- Function* Func = BB->getParent();
- BasicBlock* NewExceptBB = BasicBlock::Create(II.getContext(),
- "InvokeExcept", Func);
-
- // If this is a longjmp exception, then branch to the preliminary BB of
- // the longjmp exception handling. Otherwise, go to the old exception.
- CallInst* IsLJExcept = CallInst::Create(IsLJException, "IsLJExcept",
- NewExceptBB);
-
- BranchInst::Create(PrelimBBMap[Func], ExceptBB, IsLJExcept, NewExceptBB);
-
- II.setUnwindDest(NewExceptBB);
- ++InvokesTransformed;
-}
-
-// visitReturnInst - We want to destroy the setjmp map upon exit from the
-// function.
-void LowerSetJmp::visitReturnInst(ReturnInst &RI) {
- Function* Func = RI.getParent()->getParent();
- CallInst::Create(DestroySJMap, GetSetJmpMap(Func), "", &RI);
-}
-
-// visitUnwindInst - We want to destroy the setjmp map upon exit from the
-// function.
-void LowerSetJmp::visitUnwindInst(UnwindInst &UI) {
- Function* Func = UI.getParent()->getParent();
- CallInst::Create(DestroySJMap, GetSetJmpMap(Func), "", &UI);
-}
-
-ModulePass *llvm::createLowerSetJmpPass() {
- return new LowerSetJmp();
-}
-
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