1 //===- SjLjEHPass.cpp - Eliminate Invoke & Unwind instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation is designed for use by code generators which use SjLj
11 // based exception handling.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "sjljehprepare"
16 #include "llvm/Transforms/Scalar.h"
17 #include "llvm/Constants.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Intrinsics.h"
21 #include "llvm/LLVMContext.h"
22 #include "llvm/Module.h"
23 #include "llvm/Pass.h"
24 #include "llvm/CodeGen/Passes.h"
25 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
26 #include "llvm/Transforms/Utils/Local.h"
27 #include "llvm/ADT/Statistic.h"
28 #include "llvm/ADT/SmallVector.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Target/TargetLowering.h"
35 STATISTIC(NumInvokes, "Number of invokes replaced");
36 STATISTIC(NumUnwinds, "Number of unwinds replaced");
37 STATISTIC(NumSpilled, "Number of registers live across unwind edges");
40 class SjLjEHPass : public FunctionPass {
42 const TargetLowering *TLI;
44 const Type *FunctionContextTy;
46 Constant *UnregisterFn;
47 Constant *BuiltinSetjmpFn;
48 Constant *FrameAddrFn;
49 Constant *StackAddrFn;
50 Constant *StackRestoreFn;
54 Constant *ExceptionFn;
59 static char ID; // Pass identification, replacement for typeid
60 explicit SjLjEHPass(const TargetLowering *tli = NULL)
61 : FunctionPass(&ID), TLI(tli) { }
62 bool doInitialization(Module &M);
63 bool runOnFunction(Function &F);
65 virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
66 const char *getPassName() const {
67 return "SJLJ Exception Handling preparation";
71 void insertCallSiteStore(Instruction *I, int Number, Value *CallSite);
72 void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite,
73 SwitchInst *CatchSwitch);
74 void splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes);
75 bool insertSjLjEHSupport(Function &F);
77 } // end anonymous namespace
79 char SjLjEHPass::ID = 0;
81 // Public Interface To the SjLjEHPass pass.
82 FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) {
83 return new SjLjEHPass(TLI);
85 // doInitialization - Set up decalarations and types needed to process
87 bool SjLjEHPass::doInitialization(Module &M) {
88 // Build the function context structure.
89 // builtin_setjmp uses a five word jbuf
90 const Type *VoidPtrTy =
91 Type::getInt8PtrTy(M.getContext());
92 const Type *Int32Ty = Type::getInt32Ty(M.getContext());
94 StructType::get(M.getContext(),
97 ArrayType::get(Int32Ty, 4), // __data
98 VoidPtrTy, // __personality
100 ArrayType::get(VoidPtrTy, 5), // __jbuf
102 RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register",
103 Type::getVoidTy(M.getContext()),
104 PointerType::getUnqual(FunctionContextTy),
107 M.getOrInsertFunction("_Unwind_SjLj_Unregister",
108 Type::getVoidTy(M.getContext()),
109 PointerType::getUnqual(FunctionContextTy),
111 FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress);
112 StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
113 StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
114 BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp);
115 LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda);
116 SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector);
117 ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception);
118 CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite);
124 /// insertCallSiteStore - Insert a store of the call-site value to the
126 void SjLjEHPass::insertCallSiteStore(Instruction *I, int Number,
128 ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()),
130 // Insert a store of the call-site number
131 new StoreInst(CallSiteNoC, CallSite, true, I); // volatile
134 /// markInvokeCallSite - Insert code to mark the call_site for this invoke
135 void SjLjEHPass::markInvokeCallSite(InvokeInst *II, int InvokeNo,
137 SwitchInst *CatchSwitch) {
138 ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()),
140 // The runtime comes back to the dispatcher with the call_site - 1 in
141 // the context. Odd, but there it is.
142 ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
145 // If the unwind edge has phi nodes, split the edge.
146 if (isa<PHINode>(II->getUnwindDest()->begin())) {
147 SplitCriticalEdge(II, 1, this);
149 // If there are any phi nodes left, they must have a single predecessor.
150 while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
151 PN->replaceAllUsesWith(PN->getIncomingValue(0));
152 PN->eraseFromParent();
156 // Insert the store of the call site value
157 insertCallSiteStore(II, InvokeNo, CallSite);
159 // Record the call site value for the back end so it stays associated with
161 CallInst::Create(CallSiteFn, CallSiteNoC, "", II);
163 // Add a switch case to our unwind block.
164 CatchSwitch->addCase(SwitchValC, II->getUnwindDest());
165 // We still want this to look like an invoke so we emit the LSDA properly,
166 // so we don't transform the invoke into a call here.
169 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
170 /// we reach blocks we've already seen.
171 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
172 if (!LiveBBs.insert(BB).second) return; // already been here.
174 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
175 MarkBlocksLiveIn(*PI, LiveBBs);
178 /// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge
179 /// we spill into a stack location, guaranteeing that there is nothing live
180 /// across the unwind edge. This process also splits all critical edges
181 /// coming out of invoke's.
183 splitLiveRangesLiveAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) {
184 // First step, split all critical edges from invoke instructions.
185 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
186 InvokeInst *II = Invokes[i];
187 SplitCriticalEdge(II, 0, this);
188 SplitCriticalEdge(II, 1, this);
189 assert(!isa<PHINode>(II->getNormalDest()) &&
190 !isa<PHINode>(II->getUnwindDest()) &&
191 "critical edge splitting left single entry phi nodes?");
194 Function *F = Invokes.back()->getParent()->getParent();
196 // To avoid having to handle incoming arguments specially, we lower each arg
197 // to a copy instruction in the entry block. This ensures that the argument
198 // value itself cannot be live across the entry block.
199 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
200 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
201 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
202 ++AfterAllocaInsertPt;
203 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
205 // This is always a no-op cast because we're casting AI to AI->getType() so
206 // src and destination types are identical. BitCast is the only possibility.
207 CastInst *NC = new BitCastInst(
208 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
209 AI->replaceAllUsesWith(NC);
210 // Normally its is forbidden to replace a CastInst's operand because it
211 // could cause the opcode to reflect an illegal conversion. However, we're
212 // replacing it here with the same value it was constructed with to simply
214 NC->setOperand(0, AI);
217 // Finally, scan the code looking for instructions with bad live ranges.
218 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
219 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
220 // Ignore obvious cases we don't have to handle. In particular, most
221 // instructions either have no uses or only have a single use inside the
222 // current block. Ignore them quickly.
223 Instruction *Inst = II;
224 if (Inst->use_empty()) continue;
225 if (Inst->hasOneUse() &&
226 cast<Instruction>(Inst->use_back())->getParent() == BB &&
227 !isa<PHINode>(Inst->use_back())) continue;
229 // If this is an alloca in the entry block, it's not a real register
231 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
232 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
235 // Avoid iterator invalidation by copying users to a temporary vector.
236 SmallVector<Instruction*,16> Users;
237 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
239 Instruction *User = cast<Instruction>(*UI);
240 if (User->getParent() != BB || isa<PHINode>(User))
241 Users.push_back(User);
244 // Find all of the blocks that this value is live in.
245 std::set<BasicBlock*> LiveBBs;
246 LiveBBs.insert(Inst->getParent());
247 while (!Users.empty()) {
248 Instruction *U = Users.back();
251 if (!isa<PHINode>(U)) {
252 MarkBlocksLiveIn(U->getParent(), LiveBBs);
254 // Uses for a PHI node occur in their predecessor block.
255 PHINode *PN = cast<PHINode>(U);
256 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
257 if (PN->getIncomingValue(i) == Inst)
258 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
262 // Now that we know all of the blocks that this thing is live in, see if
263 // it includes any of the unwind locations.
264 bool NeedsSpill = false;
265 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
266 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
267 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
272 // If we decided we need a spill, do it.
275 DemoteRegToStack(*Inst, true);
280 bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
281 SmallVector<ReturnInst*,16> Returns;
282 SmallVector<UnwindInst*,16> Unwinds;
283 SmallVector<InvokeInst*,16> Invokes;
285 // Look through the terminators of the basic blocks to find invokes, returns
287 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
288 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
289 // Remember all return instructions in case we insert an invoke into this
291 Returns.push_back(RI);
292 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
293 Invokes.push_back(II);
294 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
295 Unwinds.push_back(UI);
298 // If we don't have any invokes or unwinds, there's nothing to do.
299 if (Unwinds.empty() && Invokes.empty()) return false;
301 // Find the eh.selector.*, eh.exception and alloca calls.
303 // Remember any allocas() that aren't in the entry block, as the
304 // jmpbuf saved SP will need to be updated for them.
306 // We'll use the first eh.selector to determine the right personality
307 // function to use. For SJLJ, we always use the same personality for the
308 // whole function, not on a per-selector basis.
309 // FIXME: That's a bit ugly. Better way?
310 SmallVector<CallInst*,16> EH_Selectors;
311 SmallVector<CallInst*,16> EH_Exceptions;
312 SmallVector<Instruction*,16> JmpbufUpdatePoints;
313 // Note: Skip the entry block since there's nothing there that interests
314 // us. eh.selector and eh.exception shouldn't ever be there, and we
315 // want to disregard any allocas that are there.
316 for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) {
317 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
318 if (CallInst *CI = dyn_cast<CallInst>(I)) {
319 if (CI->getCalledFunction() == SelectorFn) {
320 if (!PersonalityFn) PersonalityFn = CI->getOperand(2);
321 EH_Selectors.push_back(CI);
322 } else if (CI->getCalledFunction() == ExceptionFn) {
323 EH_Exceptions.push_back(CI);
324 } else if (CI->getCalledFunction() == StackRestoreFn) {
325 JmpbufUpdatePoints.push_back(CI);
327 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
328 JmpbufUpdatePoints.push_back(AI);
332 // If we don't have any eh.selector calls, we can't determine the personality
333 // function. Without a personality function, we can't process exceptions.
334 if (!PersonalityFn) return false;
336 NumInvokes += Invokes.size();
337 NumUnwinds += Unwinds.size();
339 if (!Invokes.empty()) {
340 // We have invokes, so we need to add register/unregister calls to get
341 // this function onto the global unwind stack.
343 // First thing we need to do is scan the whole function for values that are
344 // live across unwind edges. Each value that is live across an unwind edge
345 // we spill into a stack location, guaranteeing that there is nothing live
346 // across the unwind edge. This process also splits all critical edges
347 // coming out of invoke's.
348 splitLiveRangesLiveAcrossInvokes(Invokes);
350 BasicBlock *EntryBB = F.begin();
351 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
352 // that needs to be restored on all exits from the function. This is an
353 // alloca because the value needs to be added to the global context list.
354 unsigned Align = 4; // FIXME: Should be a TLI check?
355 AllocaInst *FunctionContext =
356 new AllocaInst(FunctionContextTy, 0, Align,
357 "fcn_context", F.begin()->begin());
360 const Type *Int32Ty = Type::getInt32Ty(F.getContext());
361 Value *Zero = ConstantInt::get(Int32Ty, 0);
362 // We need to also keep around a reference to the call_site field
364 Idxs[1] = ConstantInt::get(Int32Ty, 1);
365 CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
367 EntryBB->getTerminator());
369 // The exception selector comes back in context->data[1]
370 Idxs[1] = ConstantInt::get(Int32Ty, 2);
371 Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
373 EntryBB->getTerminator());
374 Idxs[1] = ConstantInt::get(Int32Ty, 1);
375 Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2,
377 EntryBB->getTerminator());
378 // The exception value comes back in context->data[0]
380 Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, Idxs+2,
382 EntryBB->getTerminator());
384 // The result of the eh.selector call will be replaced with a
385 // a reference to the selector value returned in the function
386 // context. We leave the selector itself so the EH analysis later
388 for (int i = 0, e = EH_Selectors.size(); i < e; ++i) {
389 CallInst *I = EH_Selectors[i];
390 Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I);
391 I->replaceAllUsesWith(SelectorVal);
393 // eh.exception calls are replaced with references to the proper
394 // location in the context. Unlike eh.selector, the eh.exception
395 // calls are removed entirely.
396 for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) {
397 CallInst *I = EH_Exceptions[i];
398 // Possible for there to be duplicates, so check to make sure
399 // the instruction hasn't already been removed.
400 if (!I->getParent()) continue;
401 Value *Val = new LoadInst(ExceptionAddr, "exception", true, I);
402 const Type *Ty = Type::getInt8PtrTy(F.getContext());
403 Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I);
405 I->replaceAllUsesWith(Val);
406 I->eraseFromParent();
409 // The entry block changes to have the eh.sjlj.setjmp, with a conditional
410 // branch to a dispatch block for non-zero returns. If we return normally,
411 // we're not handling an exception and just register the function context
414 // Create the dispatch block. The dispatch block is basically a big switch
415 // statement that goes to all of the invoke landing pads.
416 BasicBlock *DispatchBlock =
417 BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F);
419 // Insert a load in the Catch block, and a switch on its value. By default,
420 // we go to a block that just does an unwind (which is the correct action
421 // for a standard call).
422 BasicBlock *UnwindBlock =
423 BasicBlock::Create(F.getContext(), "unwindbb", &F);
424 Unwinds.push_back(new UnwindInst(F.getContext(), UnwindBlock));
426 Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true,
428 SwitchInst *DispatchSwitch =
429 SwitchInst::Create(DispatchLoad, UnwindBlock, Invokes.size(),
431 // Split the entry block to insert the conditional branch for the setjmp.
432 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
433 "eh.sjlj.setjmp.cont");
435 // Populate the Function Context
437 // 2. Personality function address
438 // 3. jmpbuf (save SP, FP and call eh.sjlj.setjmp)
442 Idxs[1] = ConstantInt::get(Int32Ty, 4);
443 Value *LSDAFieldPtr =
444 GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
446 EntryBB->getTerminator());
447 Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr",
448 EntryBB->getTerminator());
449 new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator());
451 Idxs[1] = ConstantInt::get(Int32Ty, 3);
452 Value *PersonalityFieldPtr =
453 GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
455 EntryBB->getTerminator());
456 new StoreInst(PersonalityFn, PersonalityFieldPtr, true,
457 EntryBB->getTerminator());
459 // Save the frame pointer.
460 Idxs[1] = ConstantInt::get(Int32Ty, 5);
462 = GetElementPtrInst::Create(FunctionContext, Idxs, Idxs+2,
464 EntryBB->getTerminator());
465 Idxs[1] = ConstantInt::get(Int32Ty, 0);
467 GetElementPtrInst::Create(JBufPtr, Idxs, Idxs+2, "jbuf_fp_gep",
468 EntryBB->getTerminator());
470 Value *Val = CallInst::Create(FrameAddrFn,
471 ConstantInt::get(Int32Ty, 0),
473 EntryBB->getTerminator());
474 new StoreInst(Val, FramePtr, true, EntryBB->getTerminator());
476 // Save the stack pointer.
477 Idxs[1] = ConstantInt::get(Int32Ty, 2);
479 GetElementPtrInst::Create(JBufPtr, Idxs, Idxs+2, "jbuf_sp_gep",
480 EntryBB->getTerminator());
482 Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator());
483 new StoreInst(Val, StackPtr, true, EntryBB->getTerminator());
485 // Call the setjmp instrinsic. It fills in the rest of the jmpbuf.
487 CastInst::Create(Instruction::BitCast, JBufPtr,
488 Type::getInt8PtrTy(F.getContext()), "",
489 EntryBB->getTerminator());
490 Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg,
492 EntryBB->getTerminator());
493 // check the return value of the setjmp. non-zero goes to dispatcher.
494 Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
495 ICmpInst::ICMP_EQ, DispatchVal, Zero,
497 // Nuke the uncond branch.
498 EntryBB->getTerminator()->eraseFromParent();
500 // Put in a new condbranch in its place.
501 BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB);
503 // Register the function context and make sure it's known to not throw
505 CallInst::Create(RegisterFn, FunctionContext, "",
506 ContBlock->getTerminator());
507 Register->setDoesNotThrow();
509 // At this point, we are all set up, update the invoke instructions
510 // to mark their call_site values, and fill in the dispatch switch
512 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
513 markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch);
515 // Mark call instructions that aren't nounwind as no-action
516 // (call_site == -1). Skip the entry block, as prior to then, no function
517 // context has been created for this function and any unexpected exceptions
518 // thrown will go directly to the caller's context, which is what we want
519 // anyway, so no need to do anything here.
520 for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) {
521 for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I)
522 if (CallInst *CI = dyn_cast<CallInst>(I)) {
523 // Ignore calls to the EH builtins (eh.selector, eh.exception)
524 Constant *Callee = CI->getCalledFunction();
525 if (Callee != SelectorFn && Callee != ExceptionFn
526 && !CI->doesNotThrow())
527 insertCallSiteStore(CI, -1, CallSite);
531 // Replace all unwinds with a branch to the unwind handler.
532 // ??? Should this ever happen with sjlj exceptions?
533 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
534 BranchInst::Create(UnwindBlock, Unwinds[i]);
535 Unwinds[i]->eraseFromParent();
538 // Following any allocas not in the entry block, update the saved SP
539 // in the jmpbuf to the new value.
540 for (unsigned i = 0, e = JmpbufUpdatePoints.size(); i != e; ++i) {
541 Instruction *AI = JmpbufUpdatePoints[i];
542 Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp");
543 StackAddr->insertAfter(AI);
544 Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true);
545 StoreStackAddr->insertAfter(StackAddr);
548 // Finally, for any returns from this function, if this function contains an
549 // invoke, add a call to unregister the function context.
550 for (unsigned i = 0, e = Returns.size(); i != e; ++i)
551 CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]);
557 bool SjLjEHPass::runOnFunction(Function &F) {
558 bool Res = insertSjLjEHSupport(F);