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llvm-mirror/lib/CodeGen/SjLjEHPrepare.cpp
Jim Grosbach a09b5ac346 PR4747 
Shared landing pads run into trouble with SJLJ, as the dispatch table is
mapped to call sites, and merging the pads will throw that off. There needs
to be a one-to-one mapping of landing pad exception table entries to invoke
call points.

Detecting the shared pad during lowering of SJLJ info insn't sufficient, as
the dispatch function may still need separate destinations to properly
handle phi-nodes.

llvm-svn: 80530
2009-08-31 01:35:03 +00:00

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//===- SjLjEHPass.cpp - Eliminate Invoke & Unwind instructions -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This transformation is designed for use by code generators which use SjLj
// based exception handling.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sjljehprepare"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLowering.h"
using namespace llvm;
STATISTIC(NumInvokes, "Number of invokes replaced");
STATISTIC(NumUnwinds, "Number of unwinds replaced");
STATISTIC(NumSpilled, "Number of registers live across unwind edges");
namespace {
class VISIBILITY_HIDDEN SjLjEHPass : public FunctionPass {
const TargetLowering *TLI;
const Type *FunctionContextTy;
Constant *RegisterFn;
Constant *UnregisterFn;
Constant *ResumeFn;
Constant *BuiltinSetjmpFn;
Constant *FrameAddrFn;
Constant *LSDAAddrFn;
Value *PersonalityFn;
Constant *Selector32Fn;
Constant *Selector64Fn;
Constant *ExceptionFn;
Value *CallSite;
public:
static char ID; // Pass identification, replacement for typeid
explicit SjLjEHPass(const TargetLowering *tli = NULL)
: FunctionPass(&ID), TLI(tli) { }
bool doInitialization(Module &M);
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
const char *getPassName() const {
return "SJLJ Exception Handling preparation";
}
private:
void markInvokeCallSite(InvokeInst *II, unsigned InvokeNo,
Value *CallSite,
SwitchInst *CatchSwitch);
void splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes);
bool insertSjLjEHSupport(Function &F);
};
} // end anonymous namespace
char SjLjEHPass::ID = 0;
// Public Interface To the SjLjEHPass pass.
FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) {
return new SjLjEHPass(TLI);
}
// doInitialization - Set up decalarations and types needed to process
// exceptions.
bool SjLjEHPass::doInitialization(Module &M) {
// Build the function context structure.
// builtin_setjmp uses a five word jbuf
const Type *VoidPtrTy =
PointerType::getUnqual(Type::getInt8Ty(M.getContext()));
const Type *Int32Ty = Type::getInt32Ty(M.getContext());
FunctionContextTy =
StructType::get(M.getContext(),
VoidPtrTy, // __prev
Int32Ty, // call_site
ArrayType::get(Int32Ty, 4), // __data
VoidPtrTy, // __personality
VoidPtrTy, // __lsda
ArrayType::get(VoidPtrTy, 5), // __jbuf
NULL);
RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register",
Type::getVoidTy(M.getContext()),
PointerType::getUnqual(FunctionContextTy),
(Type *)0);
UnregisterFn =
M.getOrInsertFunction("_Unwind_SjLj_Unregister",
Type::getVoidTy(M.getContext()),
PointerType::getUnqual(FunctionContextTy),
(Type *)0);
ResumeFn =
M.getOrInsertFunction("_Unwind_SjLj_Resume",
Type::getVoidTy(M.getContext()),
VoidPtrTy,
(Type *)0);
FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress);
BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp);
LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda);
Selector32Fn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector_i32);
Selector64Fn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector_i64);
ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception);
PersonalityFn = 0;
return true;
}
/// markInvokeCallSite - Insert code to mark the call_site for this invoke
void SjLjEHPass::markInvokeCallSite(InvokeInst *II, unsigned InvokeNo,
Value *CallSite,
SwitchInst *CatchSwitch) {
ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()),
InvokeNo);
// The runtime comes back to the dispatcher with the call_site - 1 in
// the context. Odd, but there it is.
ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
InvokeNo - 1);
// If the unwind edge has phi nodes, split the edge.
if (isa<PHINode>(II->getUnwindDest()->begin())) {
SplitCriticalEdge(II, 1, this);
// If there are any phi nodes left, they must have a single predecessor.
while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
PN->replaceAllUsesWith(PN->getIncomingValue(0));
PN->eraseFromParent();
}
}
// Insert a store of the invoke num before the invoke and store zero into the
// location afterward.
new StoreInst(CallSiteNoC, CallSite, true, II); // volatile
// Add a switch case to our unwind block.
CatchSwitch->addCase(SwitchValC, II->getUnwindDest());
// We still want this to look like an invoke so we emit the LSDA properly
// FIXME: ??? Or will this cause strangeness with mis-matched IDs like
// when it was in the front end?
}
/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
/// we reach blocks we've already seen.
static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
if (!LiveBBs.insert(BB).second) return; // already been here.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
MarkBlocksLiveIn(*PI, LiveBBs);
}
/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge
/// we spill into a stack location, guaranteeing that there is nothing live
/// across the unwind edge. This process also splits all critical edges
/// coming out of invoke's.
void SjLjEHPass::
splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) {
// First step, split all critical edges from invoke instructions.
for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
InvokeInst *II = Invokes[i];
SplitCriticalEdge(II, 0, this);
SplitCriticalEdge(II, 1, this);
assert(!isa<PHINode>(II->getNormalDest()) &&
!isa<PHINode>(II->getUnwindDest()) &&
"critical edge splitting left single entry phi nodes?");
}
Function *F = Invokes.back()->getParent()->getParent();
// To avoid having to handle incoming arguments specially, we lower each arg
// to a copy instruction in the entry block. This ensures that the argument
// value itself cannot be live across the entry block.
BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
while (isa<AllocaInst>(AfterAllocaInsertPt) &&
isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
++AfterAllocaInsertPt;
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI) {
// This is always a no-op cast because we're casting AI to AI->getType() so
// src and destination types are identical. BitCast is the only possibility.
CastInst *NC = new BitCastInst(
AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
AI->replaceAllUsesWith(NC);
// Normally its is forbidden to replace a CastInst's operand because it
// could cause the opcode to reflect an illegal conversion. However, we're
// replacing it here with the same value it was constructed with to simply
// make NC its user.
NC->setOperand(0, AI);
}
// Finally, scan the code looking for instructions with bad live ranges.
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
// Ignore obvious cases we don't have to handle. In particular, most
// instructions either have no uses or only have a single use inside the
// current block. Ignore them quickly.
Instruction *Inst = II;
if (Inst->use_empty()) continue;
if (Inst->hasOneUse() &&
cast<Instruction>(Inst->use_back())->getParent() == BB &&
!isa<PHINode>(Inst->use_back())) continue;
// If this is an alloca in the entry block, it's not a real register
// value.
if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
continue;
// Avoid iterator invalidation by copying users to a temporary vector.
SmallVector<Instruction*,16> Users;
for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (User->getParent() != BB || isa<PHINode>(User))
Users.push_back(User);
}
// Find all of the blocks that this value is live in.
std::set<BasicBlock*> LiveBBs;
LiveBBs.insert(Inst->getParent());
while (!Users.empty()) {
Instruction *U = Users.back();
Users.pop_back();
if (!isa<PHINode>(U)) {
MarkBlocksLiveIn(U->getParent(), LiveBBs);
} else {
// Uses for a PHI node occur in their predecessor block.
PHINode *PN = cast<PHINode>(U);
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == Inst)
MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
}
}
// Now that we know all of the blocks that this thing is live in, see if
// it includes any of the unwind locations.
bool NeedsSpill = false;
for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
NeedsSpill = true;
}
}
// If we decided we need a spill, do it.
if (NeedsSpill) {
++NumSpilled;
DemoteRegToStack(*Inst, true);
}
}
}
bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
SmallVector<ReturnInst*,16> Returns;
SmallVector<UnwindInst*,16> Unwinds;
SmallVector<InvokeInst*,16> Invokes;
// Look through the terminators of the basic blocks to find invokes, returns
// and unwinds
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
// Remember all return instructions in case we insert an invoke into this
// function.
Returns.push_back(RI);
} else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
Invokes.push_back(II);
} else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
Unwinds.push_back(UI);
}
// If we don't have any invokes or unwinds, there's nothing to do.
if (Unwinds.empty() && Invokes.empty()) return false;
// Find the eh.selector.* and eh.exception calls. We'll use the first
// eh.selector to determine the right personality function to use. For
// SJLJ, we always use the same personality for the whole function,
// not on a per-selector basis.
// FIXME: That's a bit ugly. Better way?
SmallVector<CallInst*,16> EH_Selectors;
SmallVector<CallInst*,16> EH_Exceptions;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
if (CallInst *CI = dyn_cast<CallInst>(I)) {
if (CI->getCalledFunction() == Selector32Fn ||
CI->getCalledFunction() == Selector64Fn) {
if (!PersonalityFn) PersonalityFn = CI->getOperand(2);
EH_Selectors.push_back(CI);
} else if (CI->getCalledFunction() == ExceptionFn) {
EH_Exceptions.push_back(CI);
}
}
}
}
// If we don't have any eh.selector calls, we can't determine the personality
// function. Without a personality function, we can't process exceptions.
if (!PersonalityFn) return false;
NumInvokes += Invokes.size();
NumUnwinds += Unwinds.size();
if (!Invokes.empty()) {
// We have invokes, so we need to add register/unregister calls to get
// this function onto the global unwind stack.
//
// First thing we need to do is scan the whole function for values that are
// live across unwind edges. Each value that is live across an unwind edge
// we spill into a stack location, guaranteeing that there is nothing live
// across the unwind edge. This process also splits all critical edges
// coming out of invoke's.
splitLiveRangesLiveAcrossInvokes(Invokes);
BasicBlock *EntryBB = F.begin();
// Create an alloca for the incoming jump buffer ptr and the new jump buffer
// that needs to be restored on all exits from the function. This is an
// alloca because the value needs to be added to the global context list.
unsigned Align = 4; // FIXME: Should be a TLI check?
AllocaInst *FunctionContext =
new AllocaInst(FunctionContextTy, 0, Align,
"fcn_context", F.begin()->begin());
Value *Idxs[2];
const Type *Int32Ty = Type::getInt32Ty(F.getContext());
Value *Zero = ConstantInt::get(Int32Ty, 0);
// We need to also keep around a reference to the call_site field
Idxs[0] = Zero;
Idxs[1] = ConstantInt::get(Int32Ty, 1);
CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
"call_site",
EntryBB->getTerminator());
// The exception selector comes back in context->data[1]
Idxs[1] = ConstantInt::get(Int32Ty, 2);
Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
"fc_data",
EntryBB->getTerminator());
Idxs[1] = ConstantInt::get(Int32Ty, 1);
Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2,
"exc_selector_gep",
EntryBB->getTerminator());
// The exception value comes back in context->data[0]
Idxs[1] = Zero;
Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2,
"exception_gep",
EntryBB->getTerminator());
// The result of the eh.selector call will be replaced with a
// a reference to the selector value returned in the function
// context. We leave the selector itself so the EH analysis later
// can use it.
for (int i = 0, e = EH_Selectors.size(); i < e; ++i) {
CallInst *I = EH_Selectors[i];
Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I);
I->replaceAllUsesWith(SelectorVal);
}
// eh.exception calls are replaced with references to the proper
// location in the context. Unlike eh.selector, the eh.exception
// calls are removed entirely.
for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) {
CallInst *I = EH_Exceptions[i];
// Possible for there to be duplicates, so check to make sure
// the instruction hasn't already been removed.
if (!I->getParent()) continue;
Value *Val = new LoadInst(ExceptionAddr, "exception", true, I);
Type *Ty = PointerType::getUnqual(Type::getInt8Ty(F.getContext()));
Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I);
I->replaceAllUsesWith(Val);
I->eraseFromParent();
}
// The entry block changes to have the eh.sjlj.setjmp, with a conditional
// branch to a dispatch block for non-zero returns. If we return normally,
// we're not handling an exception and just register the function context
// and continue.
// Create the dispatch block. The dispatch block is basically a big switch
// statement that goes to all of the invoke landing pads.
BasicBlock *DispatchBlock =
BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F);
// Insert a load in the Catch block, and a switch on its value. By default,
// we go to a block that just does an unwind (which is the correct action
// for a standard call).
BasicBlock *UnwindBlock = BasicBlock::Create(F.getContext(), "unwindbb", &F);
Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock));
Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true,
DispatchBlock);
SwitchInst *DispatchSwitch =
SwitchInst::Create(DispatchLoad, UnwindBlock, Invokes.size(), DispatchBlock);
// Split the entry block to insert the conditional branch for the setjmp.
BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
"eh.sjlj.setjmp.cont");
// Populate the Function Context
// 1. LSDA address
// 2. Personality function address
// 3. jmpbuf (save FP and call eh.sjlj.setjmp)
// LSDA address
Idxs[0] = Zero;
Idxs[1] = ConstantInt::get(Int32Ty, 4);
Value *LSDAFieldPtr =
GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
"lsda_gep",
EntryBB->getTerminator());
Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr",
EntryBB->getTerminator());
new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator());
Idxs[1] = ConstantInt::get(Int32Ty, 3);
Value *PersonalityFieldPtr =
GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
"lsda_gep",
EntryBB->getTerminator());
new StoreInst(PersonalityFn, PersonalityFieldPtr, true,
EntryBB->getTerminator());
// Save the frame pointer.
Idxs[1] = ConstantInt::get(Int32Ty, 5);
Value *FieldPtr
= GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
"jbuf_gep",
EntryBB->getTerminator());
Idxs[1] = ConstantInt::get(Int32Ty, 0);
Value *ElemPtr =
GetElementPtrInst::Create(FieldPtr, Idxs, Idxs+2, "jbuf_fp_gep",
EntryBB->getTerminator());
Value *Val = CallInst::Create(FrameAddrFn,
ConstantInt::get(Int32Ty, 0),
"fp",
EntryBB->getTerminator());
new StoreInst(Val, ElemPtr, true, EntryBB->getTerminator());
// Call the setjmp instrinsic. It fills in the rest of the jmpbuf
Value *SetjmpArg =
CastInst::Create(Instruction::BitCast, FieldPtr,
Type::getInt8Ty(F.getContext())->getPointerTo(), "",
EntryBB->getTerminator());
Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg,
"dispatch",
EntryBB->getTerminator());
// check the return value of the setjmp. non-zero goes to dispatcher
Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
ICmpInst::ICMP_EQ, DispatchVal, Zero,
"notunwind");
// Nuke the uncond branch.
EntryBB->getTerminator()->eraseFromParent();
// Put in a new condbranch in its place.
BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB);
// Register the function context and make sure it's known to not throw
CallInst *Register =
CallInst::Create(RegisterFn, FunctionContext, "",
ContBlock->getTerminator());
Register->setDoesNotThrow();
// At this point, we are all set up, update the invoke instructions
// to mark their call_site values, and fill in the dispatch switch
// accordingly.
for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch);
// The front end has likely added calls to _Unwind_Resume. We need
// to find those calls and mark the call_site as -1 immediately prior.
// resume is a noreturn function, so any block that has a call to it
// should end in an 'unreachable' instruction with the call immediately
// prior. That's how we'll search.
// ??? There's got to be a better way. this is fugly.
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if ((dyn_cast<UnreachableInst>(BB->getTerminator()))) {
BasicBlock::iterator I = BB->getTerminator();
// Check the previous instruction and see if it's a resume call
if (I == BB->begin()) continue;
if (CallInst *CI = dyn_cast<CallInst>(--I)) {
if (CI->getCalledFunction() == ResumeFn) {
Value *NegativeOne = Constant::getAllOnesValue(Int32Ty);
new StoreInst(NegativeOne, CallSite, true, I); // volatile
}
}
}
// Replace all unwinds with a branch to the unwind handler.
// ??? Should this ever happen with sjlj exceptions?
for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
BranchInst::Create(UnwindBlock, Unwinds[i]);
Unwinds[i]->eraseFromParent();
}
// Finally, for any returns from this function, if this function contains an
// invoke, add a call to unregister the function context.
for (unsigned i = 0, e = Returns.size(); i != e; ++i)
CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]);
}
return true;
}
bool SjLjEHPass::runOnFunction(Function &F) {
bool Res = insertSjLjEHSupport(F);
return Res;
}
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