From 6f99eb56c337b7c522cb31de30765f1c37acf0bc Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 15 Sep 2003 04:56:27 +0000 Subject: [PATCH] Initial checkin of the Setjmp/Longjmp lowering/transformation pass, contributed by the masterful Bill Wendling! llvm-svn: 8520 --- llvm/lib/Transforms/IPO/LowerSetJmp.cpp | 501 ++++++++++++++++++++++++ 1 file changed, 501 insertions(+) create mode 100644 llvm/lib/Transforms/IPO/LowerSetJmp.cpp diff --git a/llvm/lib/Transforms/IPO/LowerSetJmp.cpp b/llvm/lib/Transforms/IPO/LowerSetJmp.cpp new file mode 100644 index 000000000000..e0d167a1a1e6 --- /dev/null +++ b/llvm/lib/Transforms/IPO/LowerSetJmp.cpp @@ -0,0 +1,501 @@ +//===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===// +// +// This file implements the lowering of setjmp and longjmp to use the +// LLVM invoke instruction 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. +//===----------------------------------------------------------------------===// + +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/Instructions.h" +#include "llvm/Intrinsics.h" +#include "llvm/Module.h" +#include "llvm/Pass.h" +#include "llvm/Support/InstIterator.h" +#include "llvm/Support/InstVisitor.h" +#include "Support/Statistic.h" +#include "Support/StringExtras.h" +#include "Support/VectorExtras.h" + +#include + +namespace { + Statistic<> LongJmpsTransformed("lowersetjmp", + "Number of longjmps transformed"); + Statistic<> SetJmpsTransformed("lowersetjmp", + "Number of setjmps transformed"); + + //===--------------------------------------------------------------------===// + // LowerSetJmp pass implementation. This is subclassed from the "Pass" + // class because it works on a module as a whole, not a function at a + // time. + + class LowerSetJmp : public Pass, + public InstVisitor { + // LLVM library functions... + Function* InitSJMap; // __llvm_sjljeh_init_setjmpmap + Function* DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap + Function* AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map + Function* ThrowLongJmp; // __llvm_sjljeh_throw_longjmp + Function* TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception + Function* IsLJException; // __llvm_sjljeh_is_longjmp_exception + Function* GetLJValue; // __llvm_sjljeh_get_longjmp_value + + typedef std::pair SwitchValuePair; + + // 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 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 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 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 SwitchValMap; + + // A map of which setjmps we've seen so far in a function. + std::map 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(const std::string& Name); + public: + void visitCallInst(CallInst& CI); + void visitInvokeInst(InvokeInst& II); + void visitReturnInst(ReturnInst& RI); + void visitUnwindInst(UnwindInst& UI); + + bool run(Module& M); + bool doInitialization(Module& M); + }; + + RegisterOpt X("lowersetjmp", "Lower Set Jump"); +} // end anonymous namespace + +// 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::run(Module& M) +{ + bool Changed = false; + + // These are what the functions are called. + Function* SetJmp = M.getNamedFunction("llvm.setjmp"); + Function* LongJmp = M.getNamedFunction("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) + while (!SetJmp->use_empty()) { + assert(isa(SetJmp->use_back()) && + "User of setjmp intrinsic not a call?"); + TransformSetJmpCall(cast(SetJmp->use_back())); + Changed = true; + } + + if (LongJmp) + while (!LongJmp->use_empty()) { + assert(isa(LongJmp->use_back()) && + "User of longjmp intrinsic not a call?"); + TransformLongJmpCall(cast(LongJmp->use_back())); + Changed = true; + } + + // Now go through the affected functions and convert calls and invokes + // to new invokes... + for (std::map::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! + } + } + + 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) +{ + const Type *SBPTy = PointerType::get(Type::SByteTy); + const Type *SBPPTy = PointerType::get(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::VoidTy, SBPPTy, 0); + // void __llvm_sjljeh_destroy_setjmpmap(void**) + DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap", + Type::VoidTy, SBPPTy, 0); + + // void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned) + AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map", + Type::VoidTy, SBPPTy, SBPTy, + Type::UIntTy, 0); + + // void __llvm_sjljeh_throw_longjmp(int*, int) + ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp", + Type::VoidTy, SBPTy, Type::IntTy, 0); + + // unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **) + TryCatchLJ = + M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception", + Type::UIntTy, SBPPTy, 0); + + // bool __llvm_sjljeh_is_longjmp_exception() + IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception", + Type::BoolTy, 0); + + // int __llvm_sjljeh_get_longjmp_value() + GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value", + Type::IntTy, 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(const std::string& Name) +{ + std::string SJLJEh("__llvm_sjljeh"); + + if (Name.size() > SJLJEh.size()) { + std::string N(Name.begin(), Name.begin() + SJLJEh.size()); + return N != SJLJEh; + } + + return true; +} + +// 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) +{ + const Type* SBPTy = PointerType::get(Type::SByteTy); + + // 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 CastInst(Inst->getOperand(1), SBPTy, "LJBuf", Inst); + new CallInst(ThrowLongJmp, make_vector(CI, Inst->getOperand(2), 0), + "", 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) + new BranchInst(SVP.first->getParent(), Inst); + else + new UnwindInst(Inst); + + // Remove all insts after the branch/unwind inst. + Inst->getParent()->getInstList().erase(Inst, + Inst->getParent()->getInstList().end()); + + ++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->getEntryNode().begin(); + assert(Inst && "Couldn't find even ONE instruction in entry block!"); + + // Fill in the alloca and call to initialize the SJ map. + const Type *SBPTy = PointerType::get(Type::SByteTy); + AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst); + new CallInst(InitSJMap, make_vector(Map, 0), "", 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 = new BasicBlock("RethrowExcept", Func); + BasicBlock::InstListType& RethrowBlkIL = Rethrow->getInstList(); + + // 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. + RethrowBlkIL.push_back(new UnwindInst()); + 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 = new BasicBlock("LongJmpBlkPre", Func); + BasicBlock::InstListType& LongJmpPreIL = LongJmpPre->getInstList(); + + // Keep track of the preliminary basic block for some of the other + // transformations. + PrelimBBMap[Func] = LongJmpPre; + + // Grab the exception. + CallInst* Cond = new + CallInst(IsLJException, std::vector(), "IsLJExcept"); + LongJmpPreIL.push_back(Cond); + + // The "decision basic block" gets the number associated with the + // setjmp call returning to switch on and the value returned by + // longjmp. + BasicBlock* DecisionBB = new BasicBlock("LJDecisionBB", Func); + BasicBlock::InstListType& DecisionBBIL = DecisionBB->getInstList(); + + LongJmpPreIL.push_back(new BranchInst(DecisionBB, Rethrow, Cond)); + + // Fill in the "decision" basic block. + CallInst* LJVal = new CallInst(GetLJValue, std::vector(), "LJVal"); + DecisionBBIL.push_back(LJVal); + CallInst* SJNum = new + CallInst(TryCatchLJ, make_vector(GetSetJmpMap(Func), 0), "SJNum"); + DecisionBBIL.push_back(SJNum); + + SwitchInst* SI = new SwitchInst(SJNum, Rethrow); + DecisionBBIL.push_back(SI); + 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. + const Type* SBPTy = PointerType::get(Type::SByteTy); + CastInst* BufPtr = new CastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst); + new CallInst(AddSJToMap, + make_vector(GetSetJmpMap(Func), BufPtr, + ConstantUInt::get(Type::UIntTy, + SetJmpIDMap[Func]++), 0), + "", Inst); + + // FIXME: This is a nasty piece of code. We want the jump buffer to + // dominate all uses. However, we're doing unnatural things to the CFG + // which cause this dominance to be lost. The only way to guarantee we + // get it back is to place where the jump buffer is being allocated + // into the entry block. That's what this code does. The alloca for the + // jump buffer is followed by a getelementptr call. + if (GetElementPtrInst* GEP = dyn_cast(Inst->getOperand(1))) + if (GEP->use_size() > 1) { + if (AllocaInst* AI = dyn_cast(GEP->getPointerOperand())) { + BasicBlock& Entry = Func->getEntryNode(); + BasicBlock::InstListType& EntryIL = Entry.getInstList(); + + Instruction* NewAI = AI->clone(); + Instruction* NewGEP = GEP->clone(); + NewAI->setName(AI->getName()); + NewGEP->setName(GEP->getName()); + EntryIL.push_front(NewGEP); + EntryIL.push_front(NewAI); + GEP->replaceAllUsesWith(NewGEP); + AI->replaceAllUsesWith(NewAI); + } + } + + // 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("SetJmpContBlock"); + + // Reposition the split BB in the BB list to make things tidier. + Func->getBasicBlockList().remove(SetJmpContBlock); + Func->getBasicBlockList().insert(++Function::iterator(ABlock), + SetJmpContBlock); + + // This PHI node will be in the new block created from the + // splitBasicBlock call. + PHINode* PHI = new PHINode(Type::IntTy, "SetJmpReturn", Inst); + + // Coming from a call to setjmp, the return is 0. + PHI->addIncoming(ConstantInt::getNullValue(Type::IntTy), ABlock); + + // Add the case for this setjmp's number... + SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func)); + SVP.first->addCase(ConstantUInt::get(Type::UIntTy, 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->getParent()->getInstList().erase(Inst); + + ++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(); + BasicBlock* NewBB = OldBB->splitBasicBlock(CI); + assert(NewBB && "Couldn't split BB of \"call\" instruction!!"); + NewBB->setName("Call2Invoke"); + + // Reposition the split BB in the BB list to make things tidier. + Function* Func = OldBB->getParent(); + Func->getBasicBlockList().remove(NewBB); + Func->getBasicBlockList().insert(++Function::iterator(OldBB), NewBB); + + // Construct the new "invoke" instruction. + TerminatorInst* Term = OldBB->getTerminator(); + std::vector Params(CI.op_begin() + 1, CI.op_end()); + InvokeInst* II = new + InvokeInst(CI.getCalledValue(), NewBB, PrelimBBMap[Func], + Params, CI.getName(), Term); + + // Replace the old call inst with the invoke inst and remove the call. + CI.replaceAllUsesWith(II); + CI.getParent()->getInstList().erase(&CI); + + // The old terminator is useless now that we have the invoke inst. + Term->getParent()->getInstList().erase(Term); +} + +// 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; + + Function* Func = II.getParent()->getParent(); + + BasicBlock* NormalBB = II.getNormalDest(); + BasicBlock* ExceptBB = II.getExceptionalDest(); + + BasicBlock* NewExceptBB = new BasicBlock("InvokeExcept", Func); + BasicBlock::InstListType& InstList = NewExceptBB->getInstList(); + + // 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 = new + CallInst(IsLJException, std::vector(), "IsLJExcept"); + InstList.push_back(IsLJExcept); + + BranchInst* BR = new BranchInst(PrelimBBMap[Func], ExceptBB, IsLJExcept); + InstList.push_back(BR); + + II.setExceptionalDest(NewExceptBB); +} + +// visitReturnInst - We want to destroy the setjmp map upon exit from the +// function. +void LowerSetJmp::visitReturnInst(ReturnInst& RI) +{ + Function* Func = RI.getParent()->getParent(); + new CallInst(DestroySJMap, make_vector(GetSetJmpMap(Func), 0), + "", &RI); +} + +// visitUnwindInst - We want to destroy the setjmp map upon exit from the +// function. +void LowerSetJmp::visitUnwindInst(UnwindInst& UI) +{ + Function* Func = UI.getParent()->getParent(); + new CallInst(DestroySJMap, make_vector(GetSetJmpMap(Func), 0), + "", &UI); +} + +Pass* createLowerSetJmpPass() +{ + return new LowerSetJmp(); +}