1 //===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the lowering of setjmp and longjmp to use the
11 // LLVM invoke and unwind instructions as necessary.
13 // Lowering of longjmp is fairly trivial. We replace the call with a
14 // call to the LLVM library function "__llvm_sjljeh_throw_longjmp()".
15 // This unwinds the stack for us calling all of the destructors for
16 // objects allocated on the stack.
18 // At a setjmp call, the basic block is split and the setjmp removed.
19 // The calls in a function that have a setjmp are converted to invoke
20 // where the except part checks to see if it's a longjmp exception and,
21 // if so, if it's handled in the function. If it is, then it gets the
22 // value returned by the longjmp and goes to where the basic block was
23 // split. Invoke instructions are handled in a similar fashion with the
24 // original except block being executed if it isn't a longjmp except
25 // that is handled by that function.
27 //===----------------------------------------------------------------------===//
29 //===----------------------------------------------------------------------===//
30 // FIXME: This pass doesn't deal with PHI statements just yet. That is,
31 // we expect this to occur before SSAification is done. This would seem
32 // to make sense, but in general, it might be a good idea to make this
33 // pass invokable via the "opt" command at will.
34 //===----------------------------------------------------------------------===//
36 #include "llvm/Transforms/IPO.h"
37 #include "llvm/Constants.h"
38 #include "llvm/DerivedTypes.h"
39 #include "llvm/Instructions.h"
40 #include "llvm/Intrinsics.h"
41 #include "llvm/Module.h"
42 #include "llvm/Pass.h"
43 #include "llvm/Support/CFG.h"
44 #include "llvm/Support/InstVisitor.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 #include "llvm/ADT/DepthFirstIterator.h"
47 #include "llvm/ADT/Statistic.h"
48 #include "llvm/ADT/StringExtras.h"
49 #include "llvm/ADT/VectorExtras.h"
53 Statistic<> LongJmpsTransformed("lowersetjmp",
54 "Number of longjmps transformed");
55 Statistic<> SetJmpsTransformed("lowersetjmp",
56 "Number of setjmps transformed");
57 Statistic<> CallsTransformed("lowersetjmp",
58 "Number of calls invokified");
59 Statistic<> InvokesTransformed("lowersetjmp",
60 "Number of invokes modified");
62 //===--------------------------------------------------------------------===//
63 // LowerSetJmp pass implementation. This is subclassed from the "Pass"
64 // class because it works on a module as a whole, not a function at a
67 class LowerSetJmp : public ModulePass,
68 public InstVisitor<LowerSetJmp> {
69 // LLVM library functions...
70 Function* InitSJMap; // __llvm_sjljeh_init_setjmpmap
71 Function* DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap
72 Function* AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map
73 Function* ThrowLongJmp; // __llvm_sjljeh_throw_longjmp
74 Function* TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception
75 Function* IsLJException; // __llvm_sjljeh_is_longjmp_exception
76 Function* GetLJValue; // __llvm_sjljeh_get_longjmp_value
78 typedef std::pair<SwitchInst*, CallInst*> SwitchValuePair;
80 // Keep track of those basic blocks reachable via a depth-first search of
81 // the CFG from a setjmp call. We only need to transform those "call" and
82 // "invoke" instructions that are reachable from the setjmp call site.
83 std::set<BasicBlock*> DFSBlocks;
85 // The setjmp map is going to hold information about which setjmps
86 // were called (each setjmp gets its own number) and with which
87 // buffer it was called.
88 std::map<Function*, AllocaInst*> SJMap;
90 // The rethrow basic block map holds the basic block to branch to if
91 // the exception isn't handled in the current function and needs to
93 std::map<const Function*, BasicBlock*> RethrowBBMap;
95 // The preliminary basic block map holds a basic block that grabs the
96 // exception and determines if it's handled by the current function.
97 std::map<const Function*, BasicBlock*> PrelimBBMap;
99 // The switch/value map holds a switch inst/call inst pair. The
100 // switch inst controls which handler (if any) gets called and the
101 // value is the value returned to that handler by the call to
102 // __llvm_sjljeh_get_longjmp_value.
103 std::map<const Function*, SwitchValuePair> SwitchValMap;
105 // A map of which setjmps we've seen so far in a function.
106 std::map<const Function*, unsigned> SetJmpIDMap;
108 AllocaInst* GetSetJmpMap(Function* Func);
109 BasicBlock* GetRethrowBB(Function* Func);
110 SwitchValuePair GetSJSwitch(Function* Func, BasicBlock* Rethrow);
112 void TransformLongJmpCall(CallInst* Inst);
113 void TransformSetJmpCall(CallInst* Inst);
115 bool IsTransformableFunction(const std::string& Name);
117 void visitCallInst(CallInst& CI);
118 void visitInvokeInst(InvokeInst& II);
119 void visitReturnInst(ReturnInst& RI);
120 void visitUnwindInst(UnwindInst& UI);
122 bool runOnModule(Module& M);
123 bool doInitialization(Module& M);
126 RegisterOpt<LowerSetJmp> X("lowersetjmp", "Lower Set Jump");
127 } // end anonymous namespace
129 // run - Run the transformation on the program. We grab the function
130 // prototypes for longjmp and setjmp. If they are used in the program,
131 // then we can go directly to the places they're at and transform them.
132 bool LowerSetJmp::runOnModule(Module& M) {
133 bool Changed = false;
135 // These are what the functions are called.
136 Function* SetJmp = M.getNamedFunction("llvm.setjmp");
137 Function* LongJmp = M.getNamedFunction("llvm.longjmp");
139 // This program doesn't have longjmp and setjmp calls.
140 if ((!LongJmp || LongJmp->use_empty()) &&
141 (!SetJmp || SetJmp->use_empty())) return false;
143 // Initialize some values and functions we'll need to transform the
144 // setjmp/longjmp functions.
148 for (Value::use_iterator B = SetJmp->use_begin(), E = SetJmp->use_end();
150 BasicBlock* BB = cast<Instruction>(*B)->getParent();
151 for (df_ext_iterator<BasicBlock*> I = df_ext_begin(BB, DFSBlocks),
152 E = df_ext_end(BB, DFSBlocks); I != E; ++I)
156 while (!SetJmp->use_empty()) {
157 assert(isa<CallInst>(SetJmp->use_back()) &&
158 "User of setjmp intrinsic not a call?");
159 TransformSetJmpCall(cast<CallInst>(SetJmp->use_back()));
165 while (!LongJmp->use_empty()) {
166 assert(isa<CallInst>(LongJmp->use_back()) &&
167 "User of longjmp intrinsic not a call?");
168 TransformLongJmpCall(cast<CallInst>(LongJmp->use_back()));
172 // Now go through the affected functions and convert calls and invokes
174 for (std::map<Function*, AllocaInst*>::iterator
175 B = SJMap.begin(), E = SJMap.end(); B != E; ++B) {
176 Function* F = B->first;
177 for (Function::iterator BB = F->begin(), BE = F->end(); BB != BE; ++BB)
178 for (BasicBlock::iterator IB = BB->begin(), IE = BB->end(); IB != IE; ) {
180 if (IB != BB->end() && IB->getParent() != BB)
181 break; // The next instruction got moved to a different block!
187 RethrowBBMap.clear();
189 SwitchValMap.clear();
195 // doInitialization - For the lower long/setjmp pass, this ensures that a
196 // module contains a declaration for the intrisic functions we are going
197 // to call to convert longjmp and setjmp calls.
199 // This function is always successful, unless it isn't.
200 bool LowerSetJmp::doInitialization(Module& M)
202 const Type *SBPTy = PointerType::get(Type::SByteTy);
203 const Type *SBPPTy = PointerType::get(SBPTy);
205 // N.B. See llvm/runtime/GCCLibraries/libexception/SJLJ-Exception.h for
206 // a description of the following library functions.
208 // void __llvm_sjljeh_init_setjmpmap(void**)
209 InitSJMap = M.getOrInsertFunction("__llvm_sjljeh_init_setjmpmap",
210 Type::VoidTy, SBPPTy, 0);
211 // void __llvm_sjljeh_destroy_setjmpmap(void**)
212 DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap",
213 Type::VoidTy, SBPPTy, 0);
215 // void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned)
216 AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map",
217 Type::VoidTy, SBPPTy, SBPTy,
220 // void __llvm_sjljeh_throw_longjmp(int*, int)
221 ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp",
222 Type::VoidTy, SBPTy, Type::IntTy, 0);
224 // unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **)
226 M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception",
227 Type::UIntTy, SBPPTy, 0);
229 // bool __llvm_sjljeh_is_longjmp_exception()
230 IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception",
233 // int __llvm_sjljeh_get_longjmp_value()
234 GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value",
239 // IsTransformableFunction - Return true if the function name isn't one
240 // of the ones we don't want transformed. Currently, don't transform any
241 // "llvm.{setjmp,longjmp}" functions and none of the setjmp/longjmp error
242 // handling functions (beginning with __llvm_sjljeh_...they don't throw
244 bool LowerSetJmp::IsTransformableFunction(const std::string& Name)
246 std::string SJLJEh("__llvm_sjljeh");
248 if (Name.size() > SJLJEh.size())
249 return std::string(Name.begin(), Name.begin() + SJLJEh.size()) != SJLJEh;
254 // TransformLongJmpCall - Transform a longjmp call into a call to the
255 // internal __llvm_sjljeh_throw_longjmp function. It then takes care of
256 // throwing the exception for us.
257 void LowerSetJmp::TransformLongJmpCall(CallInst* Inst)
259 const Type* SBPTy = PointerType::get(Type::SByteTy);
261 // Create the call to "__llvm_sjljeh_throw_longjmp". This takes the
262 // same parameters as "longjmp", except that the buffer is cast to a
263 // char*. It returns "void", so it doesn't need to replace any of
264 // Inst's uses and doesn't get a name.
265 CastInst* CI = new CastInst(Inst->getOperand(1), SBPTy, "LJBuf", Inst);
266 new CallInst(ThrowLongJmp, make_vector<Value*>(CI, Inst->getOperand(2), 0),
269 SwitchValuePair& SVP = SwitchValMap[Inst->getParent()->getParent()];
271 // If the function has a setjmp call in it (they are transformed first)
272 // we should branch to the basic block that determines if this longjmp
273 // is applicable here. Otherwise, issue an unwind.
275 new BranchInst(SVP.first->getParent(), Inst);
277 new UnwindInst(Inst);
279 // Remove all insts after the branch/unwind inst.
280 Inst->getParent()->getInstList().erase(Inst,
281 Inst->getParent()->getInstList().end());
283 ++LongJmpsTransformed;
286 // GetSetJmpMap - Retrieve (create and initialize, if necessary) the
287 // setjmp map. This map is going to hold information about which setjmps
288 // were called (each setjmp gets its own number) and with which buffer it
289 // was called. There can be only one!
290 AllocaInst* LowerSetJmp::GetSetJmpMap(Function* Func)
292 if (SJMap[Func]) return SJMap[Func];
294 // Insert the setjmp map initialization before the first instruction in
296 Instruction* Inst = Func->getEntryBlock().begin();
297 assert(Inst && "Couldn't find even ONE instruction in entry block!");
299 // Fill in the alloca and call to initialize the SJ map.
300 const Type *SBPTy = PointerType::get(Type::SByteTy);
301 AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst);
302 new CallInst(InitSJMap, make_vector<Value*>(Map, 0), "", Inst);
303 return SJMap[Func] = Map;
306 // GetRethrowBB - Only one rethrow basic block is needed per function.
307 // If this is a longjmp exception but not handled in this block, this BB
308 // performs the rethrow.
309 BasicBlock* LowerSetJmp::GetRethrowBB(Function* Func)
311 if (RethrowBBMap[Func]) return RethrowBBMap[Func];
313 // The basic block we're going to jump to if we need to rethrow the
315 BasicBlock* Rethrow = new BasicBlock("RethrowExcept", Func);
317 // Fill in the "Rethrow" BB with a call to rethrow the exception. This
318 // is the last instruction in the BB since at this point the runtime
319 // should exit this function and go to the next function.
320 new UnwindInst(Rethrow);
321 return RethrowBBMap[Func] = Rethrow;
324 // GetSJSwitch - Return the switch statement that controls which handler
325 // (if any) gets called and the value returned to that handler.
326 LowerSetJmp::SwitchValuePair LowerSetJmp::GetSJSwitch(Function* Func,
329 if (SwitchValMap[Func].first) return SwitchValMap[Func];
331 BasicBlock* LongJmpPre = new BasicBlock("LongJmpBlkPre", Func);
332 BasicBlock::InstListType& LongJmpPreIL = LongJmpPre->getInstList();
334 // Keep track of the preliminary basic block for some of the other
336 PrelimBBMap[Func] = LongJmpPre;
338 // Grab the exception.
340 CallInst(IsLJException, std::vector<Value*>(), "IsLJExcept");
341 LongJmpPreIL.push_back(Cond);
343 // The "decision basic block" gets the number associated with the
344 // setjmp call returning to switch on and the value returned by
346 BasicBlock* DecisionBB = new BasicBlock("LJDecisionBB", Func);
347 BasicBlock::InstListType& DecisionBBIL = DecisionBB->getInstList();
349 new BranchInst(DecisionBB, Rethrow, Cond, LongJmpPre);
351 // Fill in the "decision" basic block.
352 CallInst* LJVal = new CallInst(GetLJValue, std::vector<Value*>(), "LJVal");
353 DecisionBBIL.push_back(LJVal);
354 CallInst* SJNum = new
355 CallInst(TryCatchLJ, make_vector<Value*>(GetSetJmpMap(Func), 0), "SJNum");
356 DecisionBBIL.push_back(SJNum);
358 SwitchInst* SI = new SwitchInst(SJNum, Rethrow, DecisionBB);
359 return SwitchValMap[Func] = SwitchValuePair(SI, LJVal);
362 // TransformSetJmpCall - The setjmp call is a bit trickier to transform.
363 // We're going to convert all setjmp calls to nops. Then all "call" and
364 // "invoke" instructions in the function are converted to "invoke" where
365 // the "except" branch is used when returning from a longjmp call.
366 void LowerSetJmp::TransformSetJmpCall(CallInst* Inst)
368 BasicBlock* ABlock = Inst->getParent();
369 Function* Func = ABlock->getParent();
371 // Add this setjmp to the setjmp map.
372 const Type* SBPTy = PointerType::get(Type::SByteTy);
373 CastInst* BufPtr = new CastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst);
374 new CallInst(AddSJToMap,
375 make_vector<Value*>(GetSetJmpMap(Func), BufPtr,
376 ConstantUInt::get(Type::UIntTy,
377 SetJmpIDMap[Func]++), 0),
380 // We are guaranteed that there are no values live across basic blocks
381 // (because we are "not in SSA form" yet), but there can still be values live
382 // in basic blocks. Because of this, splitting the setjmp block can cause
383 // values above the setjmp to not dominate uses which are after the setjmp
384 // call. For all of these occasions, we must spill the value to the stack.
386 std::set<Instruction*> InstrsAfterCall;
388 // The call is probably very close to the end of the basic block, for the
389 // common usage pattern of: 'if (setjmp(...))', so keep track of the
390 // instructions after the call.
391 for (BasicBlock::iterator I = ++BasicBlock::iterator(Inst), E = ABlock->end();
393 InstrsAfterCall.insert(I);
395 for (BasicBlock::iterator II = ABlock->begin();
396 II != BasicBlock::iterator(Inst); ++II)
397 // Loop over all of the uses of instruction. If any of them are after the
398 // call, "spill" the value to the stack.
399 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
401 if (cast<Instruction>(*UI)->getParent() != ABlock ||
402 InstrsAfterCall.count(cast<Instruction>(*UI))) {
403 DemoteRegToStack(*II);
406 InstrsAfterCall.clear();
408 // Change the setjmp call into a branch statement. We'll remove the
409 // setjmp call in a little bit. No worries.
410 BasicBlock* SetJmpContBlock = ABlock->splitBasicBlock(Inst);
411 assert(SetJmpContBlock && "Couldn't split setjmp BB!!");
413 SetJmpContBlock->setName("SetJmpContBlock");
415 // This PHI node will be in the new block created from the
416 // splitBasicBlock call.
417 PHINode* PHI = new PHINode(Type::IntTy, "SetJmpReturn", Inst);
419 // Coming from a call to setjmp, the return is 0.
420 PHI->addIncoming(ConstantInt::getNullValue(Type::IntTy), ABlock);
422 // Add the case for this setjmp's number...
423 SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func));
424 SVP.first->addCase(ConstantUInt::get(Type::UIntTy, SetJmpIDMap[Func] - 1),
427 // Value coming from the handling of the exception.
428 PHI->addIncoming(SVP.second, SVP.second->getParent());
430 // Replace all uses of this instruction with the PHI node created by
431 // the eradication of setjmp.
432 Inst->replaceAllUsesWith(PHI);
433 Inst->getParent()->getInstList().erase(Inst);
435 ++SetJmpsTransformed;
438 // visitCallInst - This converts all LLVM call instructions into invoke
439 // instructions. The except part of the invoke goes to the "LongJmpBlkPre"
440 // that grabs the exception and proceeds to determine if it's a longjmp
442 void LowerSetJmp::visitCallInst(CallInst& CI)
444 if (CI.getCalledFunction())
445 if (!IsTransformableFunction(CI.getCalledFunction()->getName()) ||
446 CI.getCalledFunction()->isIntrinsic()) return;
448 BasicBlock* OldBB = CI.getParent();
450 // If not reachable from a setjmp call, don't transform.
451 if (!DFSBlocks.count(OldBB)) return;
453 BasicBlock* NewBB = OldBB->splitBasicBlock(CI);
454 assert(NewBB && "Couldn't split BB of \"call\" instruction!!");
455 NewBB->setName("Call2Invoke");
457 Function* Func = OldBB->getParent();
459 // Construct the new "invoke" instruction.
460 TerminatorInst* Term = OldBB->getTerminator();
461 std::vector<Value*> Params(CI.op_begin() + 1, CI.op_end());
463 InvokeInst(CI.getCalledValue(), NewBB, PrelimBBMap[Func],
464 Params, CI.getName(), Term);
466 // Replace the old call inst with the invoke inst and remove the call.
467 CI.replaceAllUsesWith(II);
468 CI.getParent()->getInstList().erase(&CI);
470 // The old terminator is useless now that we have the invoke inst.
471 Term->getParent()->getInstList().erase(Term);
475 // visitInvokeInst - Converting the "invoke" instruction is fairly
476 // straight-forward. The old exception part is replaced by a query asking
477 // if this is a longjmp exception. If it is, then it goes to the longjmp
478 // exception blocks. Otherwise, control is passed the old exception.
479 void LowerSetJmp::visitInvokeInst(InvokeInst& II)
481 if (II.getCalledFunction())
482 if (!IsTransformableFunction(II.getCalledFunction()->getName()) ||
483 II.getCalledFunction()->isIntrinsic()) return;
485 BasicBlock* BB = II.getParent();
487 // If not reachable from a setjmp call, don't transform.
488 if (!DFSBlocks.count(BB)) return;
490 BasicBlock* NormalBB = II.getNormalDest();
491 BasicBlock* ExceptBB = II.getUnwindDest();
493 Function* Func = BB->getParent();
494 BasicBlock* NewExceptBB = new BasicBlock("InvokeExcept", Func);
495 BasicBlock::InstListType& InstList = NewExceptBB->getInstList();
497 // If this is a longjmp exception, then branch to the preliminary BB of
498 // the longjmp exception handling. Otherwise, go to the old exception.
499 CallInst* IsLJExcept = new
500 CallInst(IsLJException, std::vector<Value*>(), "IsLJExcept");
501 InstList.push_back(IsLJExcept);
503 new BranchInst(PrelimBBMap[Func], ExceptBB, IsLJExcept, NewExceptBB);
505 II.setUnwindDest(NewExceptBB);
506 ++InvokesTransformed;
509 // visitReturnInst - We want to destroy the setjmp map upon exit from the
511 void LowerSetJmp::visitReturnInst(ReturnInst &RI) {
512 Function* Func = RI.getParent()->getParent();
513 new CallInst(DestroySJMap, make_vector<Value*>(GetSetJmpMap(Func), 0),
517 // visitUnwindInst - We want to destroy the setjmp map upon exit from the
519 void LowerSetJmp::visitUnwindInst(UnwindInst &UI) {
520 Function* Func = UI.getParent()->getParent();
521 new CallInst(DestroySJMap, make_vector<Value*>(GetSetJmpMap(Func), 0),
525 ModulePass *llvm::createLowerSetJmpPass() {
526 return new LowerSetJmp();