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was a "major hack" :) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8524 91177308-0d34-0410-b5e6-96231b3b80d8
479 lines
19 KiB
C++
479 lines
19 KiB
C++
//===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===//
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//
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// This file implements the lowering of setjmp and longjmp to use the
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// LLVM invoke and unwind instructions as necessary.
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//
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// Lowering of longjmp is fairly trivial. We replace the call with a
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// call to the LLVM library function "__llvm_sjljeh_throw_longjmp()".
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// This unwinds the stack for us calling all of the destructors for
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// objects allocated on the stack.
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//
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// At a setjmp call, the basic block is split and the setjmp removed.
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// The calls in a function that have a setjmp are converted to invoke
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// where the except part checks to see if it's a longjmp exception and,
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// if so, if it's handled in the function. If it is, then it gets the
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// value returned by the longjmp and goes to where the basic block was
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// split. Invoke instructions are handled in a similar fashion with the
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// original except block being executed if it isn't a longjmp except
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// that is handled by that function.
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//
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// This pass was contributed to LLVM by Bill Wendling.
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//
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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// FIXME: This pass doesn't deal with PHI statements just yet. That is,
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// we expect this to occur before SSAification is done. This would seem
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// to make sense, but in general, it might be a good idea to make this
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// pass invokable via the "opt" command at will.
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//===----------------------------------------------------------------------===//
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Intrinsics.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Support/InstVisitor.h"
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#include "Support/Statistic.h"
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#include "Support/StringExtras.h"
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#include "Support/VectorExtras.h"
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#include <set>
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namespace {
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Statistic<> LongJmpsTransformed("lowersetjmp",
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"Number of longjmps transformed");
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Statistic<> SetJmpsTransformed("lowersetjmp",
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"Number of setjmps transformed");
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//===--------------------------------------------------------------------===//
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// LowerSetJmp pass implementation. This is subclassed from the "Pass"
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// class because it works on a module as a whole, not a function at a
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// time.
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class LowerSetJmp : public Pass,
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public InstVisitor<LowerSetJmp> {
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// LLVM library functions...
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Function* InitSJMap; // __llvm_sjljeh_init_setjmpmap
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Function* DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap
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Function* AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map
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Function* ThrowLongJmp; // __llvm_sjljeh_throw_longjmp
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Function* TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception
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Function* IsLJException; // __llvm_sjljeh_is_longjmp_exception
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Function* GetLJValue; // __llvm_sjljeh_get_longjmp_value
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typedef std::pair<SwitchInst*, CallInst*> SwitchValuePair;
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// The setjmp map is going to hold information about which setjmps
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// were called (each setjmp gets its own number) and with which
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// buffer it was called.
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std::map<Function*, AllocaInst*> SJMap;
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// The rethrow basic block map holds the basic block to branch to if
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// the exception isn't handled in the current function and needs to
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// be rethrown.
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std::map<const Function*, BasicBlock*> RethrowBBMap;
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// The preliminary basic block map holds a basic block that grabs the
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// exception and determines if it's handled by the current function.
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std::map<const Function*, BasicBlock*> PrelimBBMap;
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// The switch/value map holds a switch inst/call inst pair. The
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// switch inst controls which handler (if any) gets called and the
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// value is the value returned to that handler by the call to
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// __llvm_sjljeh_get_longjmp_value.
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std::map<const Function*, SwitchValuePair> SwitchValMap;
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// A map of which setjmps we've seen so far in a function.
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std::map<const Function*, unsigned> SetJmpIDMap;
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AllocaInst* GetSetJmpMap(Function* Func);
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BasicBlock* GetRethrowBB(Function* Func);
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SwitchValuePair GetSJSwitch(Function* Func, BasicBlock* Rethrow);
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void TransformLongJmpCall(CallInst* Inst);
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void TransformSetJmpCall(CallInst* Inst);
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bool IsTransformableFunction(const std::string& Name);
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public:
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void visitCallInst(CallInst& CI);
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void visitInvokeInst(InvokeInst& II);
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void visitReturnInst(ReturnInst& RI);
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void visitUnwindInst(UnwindInst& UI);
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bool run(Module& M);
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bool doInitialization(Module& M);
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};
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RegisterOpt<LowerSetJmp> X("lowersetjmp", "Lower Set Jump");
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} // end anonymous namespace
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// run - Run the transformation on the program. We grab the function
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// prototypes for longjmp and setjmp. If they are used in the program,
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// then we can go directly to the places they're at and transform them.
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bool LowerSetJmp::run(Module& M)
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{
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bool Changed = false;
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// These are what the functions are called.
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Function* SetJmp = M.getNamedFunction("llvm.setjmp");
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Function* LongJmp = M.getNamedFunction("llvm.longjmp");
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// This program doesn't have longjmp and setjmp calls.
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if ((!LongJmp || LongJmp->use_empty()) &&
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(!SetJmp || SetJmp->use_empty())) return false;
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// Initialize some values and functions we'll need to transform the
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// setjmp/longjmp functions.
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doInitialization(M);
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if (SetJmp)
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while (!SetJmp->use_empty()) {
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assert(isa<CallInst>(SetJmp->use_back()) &&
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"User of setjmp intrinsic not a call?");
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TransformSetJmpCall(cast<CallInst>(SetJmp->use_back()));
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Changed = true;
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}
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if (LongJmp)
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while (!LongJmp->use_empty()) {
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assert(isa<CallInst>(LongJmp->use_back()) &&
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"User of longjmp intrinsic not a call?");
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TransformLongJmpCall(cast<CallInst>(LongJmp->use_back()));
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Changed = true;
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}
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// Now go through the affected functions and convert calls and invokes
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// to new invokes...
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for (std::map<Function*, AllocaInst*>::iterator
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B = SJMap.begin(), E = SJMap.end(); B != E; ++B) {
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Function* F = B->first;
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for (Function::iterator BB = F->begin(), BE = F->end(); BB != BE; ++BB)
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for (BasicBlock::iterator IB = BB->begin(), IE = BB->end(); IB != IE; ) {
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visit(*IB++);
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if (IB != BB->end() && IB->getParent() != BB)
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break; // The next instruction got moved to a different block!
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}
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}
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SJMap.clear();
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RethrowBBMap.clear();
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PrelimBBMap.clear();
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SwitchValMap.clear();
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SetJmpIDMap.clear();
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return Changed;
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}
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// doInitialization - For the lower long/setjmp pass, this ensures that a
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// module contains a declaration for the intrisic functions we are going
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// to call to convert longjmp and setjmp calls.
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//
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// This function is always successful, unless it isn't.
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bool LowerSetJmp::doInitialization(Module& M)
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{
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const Type *SBPTy = PointerType::get(Type::SByteTy);
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const Type *SBPPTy = PointerType::get(SBPTy);
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// N.B. See llvm/runtime/GCCLibraries/libexception/SJLJ-Exception.h for
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// a description of the following library functions.
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// void __llvm_sjljeh_init_setjmpmap(void**)
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InitSJMap = M.getOrInsertFunction("__llvm_sjljeh_init_setjmpmap",
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Type::VoidTy, SBPPTy, 0);
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// void __llvm_sjljeh_destroy_setjmpmap(void**)
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DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap",
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Type::VoidTy, SBPPTy, 0);
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// void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned)
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AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map",
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Type::VoidTy, SBPPTy, SBPTy,
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Type::UIntTy, 0);
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// void __llvm_sjljeh_throw_longjmp(int*, int)
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ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp",
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Type::VoidTy, SBPTy, Type::IntTy, 0);
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// unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **)
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TryCatchLJ =
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M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception",
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Type::UIntTy, SBPPTy, 0);
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// bool __llvm_sjljeh_is_longjmp_exception()
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IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception",
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Type::BoolTy, 0);
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// int __llvm_sjljeh_get_longjmp_value()
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GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value",
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Type::IntTy, 0);
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return true;
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}
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// IsTransformableFunction - Return true if the function name isn't one
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// of the ones we don't want transformed. Currently, don't transform any
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// "llvm.{setjmp,longjmp}" functions and none of the setjmp/longjmp error
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// handling functions (beginning with __llvm_sjljeh_...they don't throw
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// exceptions).
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bool LowerSetJmp::IsTransformableFunction(const std::string& Name)
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{
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std::string SJLJEh("__llvm_sjljeh");
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if (Name.size() > SJLJEh.size())
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return std::string(Name.begin(), Name.begin() + SJLJEh.size()) != SJLJEh;
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return true;
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}
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// TransformLongJmpCall - Transform a longjmp call into a call to the
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// internal __llvm_sjljeh_throw_longjmp function. It then takes care of
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// throwing the exception for us.
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void LowerSetJmp::TransformLongJmpCall(CallInst* Inst)
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{
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const Type* SBPTy = PointerType::get(Type::SByteTy);
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// Create the call to "__llvm_sjljeh_throw_longjmp". This takes the
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// same parameters as "longjmp", except that the buffer is cast to a
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// char*. It returns "void", so it doesn't need to replace any of
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// Inst's uses and doesn't get a name.
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CastInst* CI = new CastInst(Inst->getOperand(1), SBPTy, "LJBuf", Inst);
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new CallInst(ThrowLongJmp, make_vector<Value*>(CI, Inst->getOperand(2), 0),
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"", Inst);
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SwitchValuePair& SVP = SwitchValMap[Inst->getParent()->getParent()];
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// If the function has a setjmp call in it (they are transformed first)
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// we should branch to the basic block that determines if this longjmp
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// is applicable here. Otherwise, issue an unwind.
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if (SVP.first)
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new BranchInst(SVP.first->getParent(), Inst);
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else
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new UnwindInst(Inst);
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// Remove all insts after the branch/unwind inst.
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Inst->getParent()->getInstList().erase(Inst,
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Inst->getParent()->getInstList().end());
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++LongJmpsTransformed;
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}
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// GetSetJmpMap - Retrieve (create and initialize, if necessary) the
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// setjmp map. This map is going to hold information about which setjmps
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// were called (each setjmp gets its own number) and with which buffer it
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// was called. There can be only one!
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AllocaInst* LowerSetJmp::GetSetJmpMap(Function* Func)
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{
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if (SJMap[Func]) return SJMap[Func];
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// Insert the setjmp map initialization before the first instruction in
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// the function.
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Instruction* Inst = Func->getEntryNode().begin();
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assert(Inst && "Couldn't find even ONE instruction in entry block!");
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// Fill in the alloca and call to initialize the SJ map.
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const Type *SBPTy = PointerType::get(Type::SByteTy);
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AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst);
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new CallInst(InitSJMap, make_vector<Value*>(Map, 0), "", Inst);
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return SJMap[Func] = Map;
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}
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// GetRethrowBB - Only one rethrow basic block is needed per function.
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// If this is a longjmp exception but not handled in this block, this BB
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// performs the rethrow.
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BasicBlock* LowerSetJmp::GetRethrowBB(Function* Func)
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{
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if (RethrowBBMap[Func]) return RethrowBBMap[Func];
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// The basic block we're going to jump to if we need to rethrow the
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// exception.
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BasicBlock* Rethrow = new BasicBlock("RethrowExcept", Func);
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BasicBlock::InstListType& RethrowBlkIL = Rethrow->getInstList();
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// Fill in the "Rethrow" BB with a call to rethrow the exception. This
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// is the last instruction in the BB since at this point the runtime
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// should exit this function and go to the next function.
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RethrowBlkIL.push_back(new UnwindInst());
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return RethrowBBMap[Func] = Rethrow;
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}
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// GetSJSwitch - Return the switch statement that controls which handler
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// (if any) gets called and the value returned to that handler.
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LowerSetJmp::SwitchValuePair LowerSetJmp::GetSJSwitch(Function* Func,
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BasicBlock* Rethrow)
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{
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if (SwitchValMap[Func].first) return SwitchValMap[Func];
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BasicBlock* LongJmpPre = new BasicBlock("LongJmpBlkPre", Func);
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BasicBlock::InstListType& LongJmpPreIL = LongJmpPre->getInstList();
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// Keep track of the preliminary basic block for some of the other
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// transformations.
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PrelimBBMap[Func] = LongJmpPre;
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// Grab the exception.
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CallInst* Cond = new
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CallInst(IsLJException, std::vector<Value*>(), "IsLJExcept");
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LongJmpPreIL.push_back(Cond);
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// The "decision basic block" gets the number associated with the
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// setjmp call returning to switch on and the value returned by
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// longjmp.
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BasicBlock* DecisionBB = new BasicBlock("LJDecisionBB", Func);
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BasicBlock::InstListType& DecisionBBIL = DecisionBB->getInstList();
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LongJmpPreIL.push_back(new BranchInst(DecisionBB, Rethrow, Cond));
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// Fill in the "decision" basic block.
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CallInst* LJVal = new CallInst(GetLJValue, std::vector<Value*>(), "LJVal");
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DecisionBBIL.push_back(LJVal);
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CallInst* SJNum = new
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CallInst(TryCatchLJ, make_vector<Value*>(GetSetJmpMap(Func), 0), "SJNum");
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DecisionBBIL.push_back(SJNum);
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SwitchInst* SI = new SwitchInst(SJNum, Rethrow);
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DecisionBBIL.push_back(SI);
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return SwitchValMap[Func] = SwitchValuePair(SI, LJVal);
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}
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// TransformSetJmpCall - The setjmp call is a bit trickier to transform.
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// We're going to convert all setjmp calls to nops. Then all "call" and
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// "invoke" instructions in the function are converted to "invoke" where
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// the "except" branch is used when returning from a longjmp call.
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void LowerSetJmp::TransformSetJmpCall(CallInst* Inst)
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{
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BasicBlock* ABlock = Inst->getParent();
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Function* Func = ABlock->getParent();
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// Add this setjmp to the setjmp map.
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const Type* SBPTy = PointerType::get(Type::SByteTy);
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CastInst* BufPtr = new CastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst);
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new CallInst(AddSJToMap,
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make_vector<Value*>(GetSetJmpMap(Func), BufPtr,
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ConstantUInt::get(Type::UIntTy,
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SetJmpIDMap[Func]++), 0),
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"", Inst);
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// Change the setjmp call into a branch statement. We'll remove the
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// setjmp call in a little bit. No worries.
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BasicBlock* SetJmpContBlock = ABlock->splitBasicBlock(Inst);
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assert(SetJmpContBlock && "Couldn't split setjmp BB!!");
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SetJmpContBlock->setName("SetJmpContBlock");
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// Reposition the split BB in the BB list to make things tidier.
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Func->getBasicBlockList().remove(SetJmpContBlock);
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Func->getBasicBlockList().insert(++Function::iterator(ABlock),
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SetJmpContBlock);
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// This PHI node will be in the new block created from the
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// splitBasicBlock call.
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PHINode* PHI = new PHINode(Type::IntTy, "SetJmpReturn", Inst);
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// Coming from a call to setjmp, the return is 0.
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PHI->addIncoming(ConstantInt::getNullValue(Type::IntTy), ABlock);
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// Add the case for this setjmp's number...
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SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func));
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SVP.first->addCase(ConstantUInt::get(Type::UIntTy, SetJmpIDMap[Func] - 1),
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SetJmpContBlock);
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// Value coming from the handling of the exception.
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PHI->addIncoming(SVP.second, SVP.second->getParent());
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// Replace all uses of this instruction with the PHI node created by
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// the eradication of setjmp.
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Inst->replaceAllUsesWith(PHI);
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Inst->getParent()->getInstList().erase(Inst);
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++SetJmpsTransformed;
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}
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// visitCallInst - This converts all LLVM call instructions into invoke
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// instructions. The except part of the invoke goes to the "LongJmpBlkPre"
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// that grabs the exception and proceeds to determine if it's a longjmp
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// exception or not.
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void LowerSetJmp::visitCallInst(CallInst& CI)
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{
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if (CI.getCalledFunction())
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if (!IsTransformableFunction(CI.getCalledFunction()->getName()) ||
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CI.getCalledFunction()->isIntrinsic()) return;
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BasicBlock* OldBB = CI.getParent();
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BasicBlock* NewBB = OldBB->splitBasicBlock(CI);
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assert(NewBB && "Couldn't split BB of \"call\" instruction!!");
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NewBB->setName("Call2Invoke");
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// Reposition the split BB in the BB list to make things tidier.
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Function* Func = OldBB->getParent();
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Func->getBasicBlockList().remove(NewBB);
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Func->getBasicBlockList().insert(++Function::iterator(OldBB), NewBB);
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// Construct the new "invoke" instruction.
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TerminatorInst* Term = OldBB->getTerminator();
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std::vector<Value*> Params(CI.op_begin() + 1, CI.op_end());
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InvokeInst* II = new
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InvokeInst(CI.getCalledValue(), NewBB, PrelimBBMap[Func],
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Params, CI.getName(), Term);
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// Replace the old call inst with the invoke inst and remove the call.
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CI.replaceAllUsesWith(II);
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CI.getParent()->getInstList().erase(&CI);
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// The old terminator is useless now that we have the invoke inst.
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Term->getParent()->getInstList().erase(Term);
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}
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// visitInvokeInst - Converting the "invoke" instruction is fairly
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// straight-forward. The old exception part is replaced by a query asking
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// if this is a longjmp exception. If it is, then it goes to the longjmp
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// exception blocks. Otherwise, control is passed the old exception.
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void LowerSetJmp::visitInvokeInst(InvokeInst& II)
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{
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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();
|
|
}
|