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Initial checkin of the Setjmp/Longjmp lowering/transformation pass, 

contributed by the masterful Bill Wendling!

llvm-svn: 8520
This commit is contained in:
Chris Lattner 2003-09-15 04:56:27 +00:00
parent da3585335b
commit 6f99eb56c3
1 changed files with 501 additions and 0 deletions
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llvm/lib/Transforms/IPO/LowerSetJmp.cpp Normal file
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//===- 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 <set>
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<LowerSetJmp> {
// 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<SwitchInst*, CallInst*> 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<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(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<LowerSetJmp> 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<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!
}
}
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<Value*>(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<Value*>(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<Value*>(), "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<Value*>(), "LJVal");
DecisionBBIL.push_back(LJVal);
CallInst* SJNum = new
CallInst(TryCatchLJ, make_vector<Value*>(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<Value*>(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<GetElementPtrInst>(Inst->getOperand(1)))
if (GEP->use_size() > 1) {
if (AllocaInst* AI = dyn_cast<AllocaInst>(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<Value*> 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<Value*>(), "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<Value*>(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<Value*>(GetSetJmpMap(Func), 0),
"", &UI);
}
Pass* createLowerSetJmpPass()
{
return new LowerSetJmp();
}