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Chris Lattner86e44452003-10-05 19:14:42 +00001//===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
Misha Brukmanfd939082005-04-21 23:48:37 +00002//
John Criswellb576c942003-10-20 19:43:21 +00003// The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
Misha Brukmanfd939082005-04-21 23:48:37 +00007//
John Criswellb576c942003-10-20 19:43:21 +00008//===----------------------------------------------------------------------===//
Chris Lattner86e44452003-10-05 19:14:42 +00009//
10// This transformation is designed for use by code generators which do not yet
Chris Lattner6d784572004-02-08 19:53:56 +000011// support stack unwinding. This pass supports two models of exception handling
12// lowering, the 'cheap' support and the 'expensive' support.
13//
14// 'Cheap' exception handling support gives the program the ability to execute
15// any program which does not "throw an exception", by turning 'invoke'
16// instructions into calls and by turning 'unwind' instructions into calls to
17// abort(). If the program does dynamically use the unwind instruction, the
18// program will print a message then abort.
19//
20// 'Expensive' exception handling support gives the full exception handling
John Criswellfe3706a2005-05-02 14:47:42 +000021// support to the program at the cost of making the 'invoke' instruction
22// really expensive. It basically inserts setjmp/longjmp calls to emulate the
23// exception handling as necessary.
Chris Lattner6d784572004-02-08 19:53:56 +000024//
25// Because the 'expensive' support slows down programs a lot, and EH is only
26// used for a subset of the programs, it must be specifically enabled by an
27// option.
Chris Lattner86e44452003-10-05 19:14:42 +000028//
Chris Lattner0e28eca2004-03-31 22:00:30 +000029// Note that after this pass runs the CFG is not entirely accurate (exceptional
30// control flow edges are not correct anymore) so only very simple things should
31// be done after the lowerinvoke pass has run (like generation of native code).
32// This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
33// support the invoke instruction yet" lowering pass.
34//
Chris Lattner86e44452003-10-05 19:14:42 +000035//===----------------------------------------------------------------------===//
36
Chris Lattnerd216e8b2006-12-19 22:17:40 +000037#define DEBUG_TYPE "lowerinvoke"
Chris Lattner86e44452003-10-05 19:14:42 +000038#include "llvm/Transforms/Scalar.h"
Chris Lattnere1c09302004-02-08 07:30:29 +000039#include "llvm/Constants.h"
40#include "llvm/DerivedTypes.h"
Chris Lattner6d784572004-02-08 19:53:56 +000041#include "llvm/Instructions.h"
Chris Lattnere1c09302004-02-08 07:30:29 +000042#include "llvm/Module.h"
Chris Lattner86e44452003-10-05 19:14:42 +000043#include "llvm/Pass.h"
Chris Lattner6d784572004-02-08 19:53:56 +000044#include "llvm/Transforms/Utils/BasicBlockUtils.h"
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +000045#include "llvm/Transforms/Utils/Local.h"
Reid Spencer551ccae2004-09-01 22:55:40 +000046#include "llvm/ADT/Statistic.h"
47#include "llvm/Support/CommandLine.h"
Chris Lattnera4f0b3a2006-08-27 12:54:02 +000048#include "llvm/Support/Compiler.h"
Duraid Madina2a0013f2006-09-04 06:21:35 +000049#include "llvm/Target/TargetLowering.h"
Chris Lattner6d784572004-02-08 19:53:56 +000050#include <csetjmp>
Reid Spencer6734b572007-02-04 00:40:42 +000051#include <set>
Chris Lattnerdead9932003-12-10 20:22:42 +000052using namespace llvm;
Brian Gaeked0fde302003-11-11 22:41:34 +000053
Chris Lattnerd216e8b2006-12-19 22:17:40 +000054STATISTIC(NumInvokes, "Number of invokes replaced");
55STATISTIC(NumUnwinds, "Number of unwinds replaced");
56STATISTIC(NumSpilled, "Number of registers live across unwind edges");
57
58static cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
Chris Lattner6d784572004-02-08 19:53:56 +000059 cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
Chris Lattner86e44452003-10-05 19:14:42 +000060
Chris Lattnerd216e8b2006-12-19 22:17:40 +000061namespace {
Chris Lattnerf4b54612006-06-28 22:08:15 +000062 class VISIBILITY_HIDDEN LowerInvoke : public FunctionPass {
Chris Lattner6d784572004-02-08 19:53:56 +000063 // Used for both models.
Chris Lattnerb76efb72007-01-07 08:12:01 +000064 Constant *WriteFn;
65 Constant *AbortFn;
Chris Lattner6d784572004-02-08 19:53:56 +000066 Value *AbortMessage;
67 unsigned AbortMessageLength;
68
69 // Used for expensive EH support.
70 const Type *JBLinkTy;
71 GlobalVariable *JBListHead;
Chris Lattnerb76efb72007-01-07 08:12:01 +000072 Constant *SetJmpFn, *LongJmpFn;
Duraid Madina2a0013f2006-09-04 06:21:35 +000073
74 // We peek in TLI to grab the target's jmp_buf size and alignment
75 const TargetLowering *TLI;
76
Chris Lattner86e44452003-10-05 19:14:42 +000077 public:
Duraid Madina2a0013f2006-09-04 06:21:35 +000078 LowerInvoke(const TargetLowering *tli = NULL) : TLI(tli) { }
Chris Lattner86e44452003-10-05 19:14:42 +000079 bool doInitialization(Module &M);
80 bool runOnFunction(Function &F);
Chris Lattnered96fe82006-05-17 21:05:27 +000081
82 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
83 // This is a cluster of orthogonal Transforms
84 AU.addPreservedID(PromoteMemoryToRegisterID);
85 AU.addPreservedID(LowerSelectID);
86 AU.addPreservedID(LowerSwitchID);
87 AU.addPreservedID(LowerAllocationsID);
88 }
89
Chris Lattner6d784572004-02-08 19:53:56 +000090 private:
Chris Lattnerb76efb72007-01-07 08:12:01 +000091 void createAbortMessage(Module *M);
Chris Lattner501825e2004-02-08 22:14:44 +000092 void writeAbortMessage(Instruction *IB);
Chris Lattner6d784572004-02-08 19:53:56 +000093 bool insertCheapEHSupport(Function &F);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +000094 void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
95 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
96 AllocaInst *InvokeNum, SwitchInst *CatchSwitch);
Chris Lattner6d784572004-02-08 19:53:56 +000097 bool insertExpensiveEHSupport(Function &F);
Chris Lattner86e44452003-10-05 19:14:42 +000098 };
99
Chris Lattner7f8897f2006-08-27 22:42:52 +0000100 RegisterPass<LowerInvoke>
Chris Lattner86e44452003-10-05 19:14:42 +0000101 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
102}
103
Chris Lattnercefc18e2004-02-13 16:16:16 +0000104const PassInfo *llvm::LowerInvokePassID = X.getPassInfo();
105
Brian Gaeked0fde302003-11-11 22:41:34 +0000106// Public Interface To the LowerInvoke pass.
Duraid Madina2a0013f2006-09-04 06:21:35 +0000107FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
108 return new LowerInvoke(TLI);
Nate Begeman14b05292005-11-05 09:21:28 +0000109}
Chris Lattner86e44452003-10-05 19:14:42 +0000110
111// doInitialization - Make sure that there is a prototype for abort in the
112// current module.
113bool LowerInvoke::doInitialization(Module &M) {
Reid Spencerc5b206b2006-12-31 05:48:39 +0000114 const Type *VoidPtrTy = PointerType::get(Type::Int8Ty);
Chris Lattnerf1d0d352004-02-09 22:48:47 +0000115 AbortMessage = 0;
Chris Lattner6d784572004-02-08 19:53:56 +0000116 if (ExpensiveEHSupport) {
Nate Begeman14b05292005-11-05 09:21:28 +0000117 // Insert a type for the linked list of jump buffers.
Chris Lattner97d2dbd2006-09-05 17:48:07 +0000118 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
119 JBSize = JBSize ? JBSize : 200;
120 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
Chris Lattnere1c09302004-02-08 07:30:29 +0000121
Chris Lattner6d784572004-02-08 19:53:56 +0000122 { // The type is recursive, so use a type holder.
123 std::vector<const Type*> Elements;
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000124 Elements.push_back(JmpBufTy);
Chris Lattner6d784572004-02-08 19:53:56 +0000125 OpaqueType *OT = OpaqueType::get();
126 Elements.push_back(PointerType::get(OT));
Chris Lattner6d784572004-02-08 19:53:56 +0000127 PATypeHolder JBLType(StructType::get(Elements));
128 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
129 JBLinkTy = JBLType.get();
Chris Lattner11b9be52004-05-28 05:02:13 +0000130 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
Chris Lattner6d784572004-02-08 19:53:56 +0000131 }
132
133 const Type *PtrJBList = PointerType::get(JBLinkTy);
134
135 // Now that we've done that, insert the jmpbuf list head global, unless it
136 // already exists.
Chris Lattner97d2dbd2006-09-05 17:48:07 +0000137 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
Chris Lattner6d784572004-02-08 19:53:56 +0000138 JBListHead = new GlobalVariable(PtrJBList, false,
139 GlobalValue::LinkOnceLinkage,
140 Constant::getNullValue(PtrJBList),
141 "llvm.sjljeh.jblist", &M);
Chris Lattner97d2dbd2006-09-05 17:48:07 +0000142 }
Reid Spencerc5b206b2006-12-31 05:48:39 +0000143 SetJmpFn = M.getOrInsertFunction("llvm.setjmp", Type::Int32Ty,
Jeff Cohen66c5fd62005-10-23 04:37:20 +0000144 PointerType::get(JmpBufTy), (Type *)0);
Chris Lattner860a1612004-02-15 22:24:27 +0000145 LongJmpFn = M.getOrInsertFunction("llvm.longjmp", Type::VoidTy,
Chris Lattner6d784572004-02-08 19:53:56 +0000146 PointerType::get(JmpBufTy),
Reid Spencerc5b206b2006-12-31 05:48:39 +0000147 Type::Int32Ty, (Type *)0);
Chris Lattner6d784572004-02-08 19:53:56 +0000148 }
149
150 // We need the 'write' and 'abort' functions for both models.
Jeff Cohen66c5fd62005-10-23 04:37:20 +0000151 AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, (Type *)0);
Chris Lattnerb76efb72007-01-07 08:12:01 +0000152 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
153 VoidPtrTy, Type::Int32Ty, (Type *)0);
Chris Lattner86e44452003-10-05 19:14:42 +0000154 return true;
155}
156
Chris Lattnerb76efb72007-01-07 08:12:01 +0000157void LowerInvoke::createAbortMessage(Module *M) {
Chris Lattner0c3b3902004-11-13 19:07:32 +0000158 if (ExpensiveEHSupport) {
159 // The abort message for expensive EH support tells the user that the
160 // program 'unwound' without an 'invoke' instruction.
161 Constant *Msg =
162 ConstantArray::get("ERROR: Exception thrown, but not caught!\n");
163 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
Misha Brukmanfd939082005-04-21 23:48:37 +0000164
Chris Lattner0c3b3902004-11-13 19:07:32 +0000165 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
166 GlobalValue::InternalLinkage,
Chris Lattnerb76efb72007-01-07 08:12:01 +0000167 Msg, "abortmsg", M);
Reid Spencerc5b206b2006-12-31 05:48:39 +0000168 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
Chris Lattner0c3b3902004-11-13 19:07:32 +0000169 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx);
170 } else {
171 // The abort message for cheap EH support tells the user that EH is not
172 // enabled.
173 Constant *Msg =
174 ConstantArray::get("Exception handler needed, but not enabled. Recompile"
175 " program with -enable-correct-eh-support.\n");
176 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
177
178 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
179 GlobalValue::InternalLinkage,
Chris Lattnerb76efb72007-01-07 08:12:01 +0000180 Msg, "abortmsg", M);
Reid Spencerc5b206b2006-12-31 05:48:39 +0000181 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
Chris Lattner0c3b3902004-11-13 19:07:32 +0000182 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, GEPIdx);
183 }
184}
185
186
Chris Lattner501825e2004-02-08 22:14:44 +0000187void LowerInvoke::writeAbortMessage(Instruction *IB) {
Chris Lattnerb76efb72007-01-07 08:12:01 +0000188 if (AbortMessage == 0)
189 createAbortMessage(IB->getParent()->getParent()->getParent());
Chris Lattner0c3b3902004-11-13 19:07:32 +0000190
Chris Lattnerb76efb72007-01-07 08:12:01 +0000191 // These are the arguments we WANT...
192 std::vector<Value*> Args;
193 Args.push_back(ConstantInt::get(Type::Int32Ty, 2));
194 Args.push_back(AbortMessage);
195 Args.push_back(ConstantInt::get(Type::Int32Ty, AbortMessageLength));
196 (new CallInst(WriteFn, Args, "", IB))->setTailCall();
Chris Lattner501825e2004-02-08 22:14:44 +0000197}
198
Chris Lattner6d784572004-02-08 19:53:56 +0000199bool LowerInvoke::insertCheapEHSupport(Function &F) {
Chris Lattner86e44452003-10-05 19:14:42 +0000200 bool Changed = false;
Chris Lattnerdead9932003-12-10 20:22:42 +0000201 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
202 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
Chris Lattner86e44452003-10-05 19:14:42 +0000203 // Insert a normal call instruction...
Chris Lattnerefd91682005-05-13 06:27:02 +0000204 CallInst *NewCall = new CallInst(II->getCalledValue(),
205 std::vector<Value*>(II->op_begin()+3,
Chris Lattner86cc4232007-02-11 01:37:51 +0000206 II->op_end()), "", II);
207 NewCall->takeName(II);
Chris Lattnerefd91682005-05-13 06:27:02 +0000208 NewCall->setCallingConv(II->getCallingConv());
Chris Lattner86e44452003-10-05 19:14:42 +0000209 II->replaceAllUsesWith(NewCall);
Misha Brukmanfd939082005-04-21 23:48:37 +0000210
Chris Lattnerdead9932003-12-10 20:22:42 +0000211 // Insert an unconditional branch to the normal destination.
Chris Lattner86e44452003-10-05 19:14:42 +0000212 new BranchInst(II->getNormalDest(), II);
213
Chris Lattnerdead9932003-12-10 20:22:42 +0000214 // Remove any PHI node entries from the exception destination.
Chris Lattneraeb2a1d2004-02-08 21:44:31 +0000215 II->getUnwindDest()->removePredecessor(BB);
Chris Lattnerdead9932003-12-10 20:22:42 +0000216
Chris Lattner86e44452003-10-05 19:14:42 +0000217 // Remove the invoke instruction now.
Chris Lattnerdead9932003-12-10 20:22:42 +0000218 BB->getInstList().erase(II);
Chris Lattner86e44452003-10-05 19:14:42 +0000219
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000220 ++NumInvokes; Changed = true;
Chris Lattnerdead9932003-12-10 20:22:42 +0000221 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
Chris Lattnere1c09302004-02-08 07:30:29 +0000222 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
Chris Lattner501825e2004-02-08 22:14:44 +0000223 writeAbortMessage(UI);
Chris Lattnere1c09302004-02-08 07:30:29 +0000224
Chris Lattner86e44452003-10-05 19:14:42 +0000225 // Insert a call to abort()
Chris Lattnera9e92112005-05-06 06:48:21 +0000226 (new CallInst(AbortFn, std::vector<Value*>(), "", UI))->setTailCall();
Chris Lattner86e44452003-10-05 19:14:42 +0000227
Chris Lattner6d784572004-02-08 19:53:56 +0000228 // Insert a return instruction. This really should be a "barrier", as it
229 // is unreachable.
Chris Lattner86e44452003-10-05 19:14:42 +0000230 new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 :
231 Constant::getNullValue(F.getReturnType()), UI);
232
233 // Remove the unwind instruction now.
Chris Lattnerdead9932003-12-10 20:22:42 +0000234 BB->getInstList().erase(UI);
Chris Lattner86e44452003-10-05 19:14:42 +0000235
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000236 ++NumUnwinds; Changed = true;
Chris Lattner86e44452003-10-05 19:14:42 +0000237 }
238 return Changed;
239}
Chris Lattner6d784572004-02-08 19:53:56 +0000240
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000241/// rewriteExpensiveInvoke - Insert code and hack the function to replace the
242/// specified invoke instruction with a call.
243void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
244 AllocaInst *InvokeNum,
245 SwitchInst *CatchSwitch) {
Reid Spencerc5b206b2006-12-31 05:48:39 +0000246 ConstantInt *InvokeNoC = ConstantInt::get(Type::Int32Ty, InvokeNo);
Chris Lattner6d784572004-02-08 19:53:56 +0000247
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000248 // Insert a store of the invoke num before the invoke and store zero into the
249 // location afterward.
250 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
Chris Lattner93e50ce2005-09-29 17:44:20 +0000251
252 BasicBlock::iterator NI = II->getNormalDest()->begin();
253 while (isa<PHINode>(NI)) ++NI;
254 // nonvolatile.
Reid Spencerc5b206b2006-12-31 05:48:39 +0000255 new StoreInst(Constant::getNullValue(Type::Int32Ty), InvokeNum, false, NI);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000256
257 // Add a switch case to our unwind block.
258 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
259
260 // Insert a normal call instruction.
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000261 CallInst *NewCall = new CallInst(II->getCalledValue(),
262 std::vector<Value*>(II->op_begin()+3,
Chris Lattner86cc4232007-02-11 01:37:51 +0000263 II->op_end()), "",
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000264 II);
Chris Lattner86cc4232007-02-11 01:37:51 +0000265 NewCall->takeName(II);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000266 NewCall->setCallingConv(II->getCallingConv());
267 II->replaceAllUsesWith(NewCall);
268
269 // Replace the invoke with an uncond branch.
270 new BranchInst(II->getNormalDest(), NewCall->getParent());
271 II->eraseFromParent();
272}
Chris Lattner6d784572004-02-08 19:53:56 +0000273
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000274/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
275/// we reach blocks we've already seen.
276static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
277 if (!LiveBBs.insert(BB).second) return; // already been here.
278
279 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
280 MarkBlocksLiveIn(*PI, LiveBBs);
281}
Chris Lattner6d784572004-02-08 19:53:56 +0000282
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000283// First thing we need to do is scan the whole function for values that are
284// live across unwind edges. Each value that is live across an unwind edge
285// we spill into a stack location, guaranteeing that there is nothing live
286// across the unwind edge. This process also splits all critical edges
287// coming out of invoke's.
288void LowerInvoke::
289splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
290 // First step, split all critical edges from invoke instructions.
291 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
292 InvokeInst *II = Invokes[i];
293 SplitCriticalEdge(II, 0, this);
294 SplitCriticalEdge(II, 1, this);
295 assert(!isa<PHINode>(II->getNormalDest()) &&
296 !isa<PHINode>(II->getUnwindDest()) &&
297 "critical edge splitting left single entry phi nodes?");
Chris Lattner6d784572004-02-08 19:53:56 +0000298 }
299
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000300 Function *F = Invokes.back()->getParent()->getParent();
301
302 // To avoid having to handle incoming arguments specially, we lower each arg
Reid Spencer3da59db2006-11-27 01:05:10 +0000303 // to a copy instruction in the entry block. This ensures that the argument
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000304 // value itself cannot be live across the entry block.
305 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
306 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
307 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
308 ++AfterAllocaInsertPt;
309 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
310 AI != E; ++AI) {
Reid Spencer3da59db2006-11-27 01:05:10 +0000311 // This is always a no-op cast because we're casting AI to AI->getType() so
312 // src and destination types are identical. BitCast is the only possibility.
313 CastInst *NC = new BitCastInst(
314 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000315 AI->replaceAllUsesWith(NC);
Reid Spencer3da59db2006-11-27 01:05:10 +0000316 // Normally its is forbidden to replace a CastInst's operand because it
317 // could cause the opcode to reflect an illegal conversion. However, we're
318 // replacing it here with the same value it was constructed with to simply
319 // make NC its user.
320 NC->setOperand(0, AI);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000321 }
322
323 // Finally, scan the code looking for instructions with bad live ranges.
324 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
325 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
326 // Ignore obvious cases we don't have to handle. In particular, most
327 // instructions either have no uses or only have a single use inside the
328 // current block. Ignore them quickly.
329 Instruction *Inst = II;
330 if (Inst->use_empty()) continue;
331 if (Inst->hasOneUse() &&
332 cast<Instruction>(Inst->use_back())->getParent() == BB &&
333 !isa<PHINode>(Inst->use_back())) continue;
334
Chris Lattner45313712005-09-27 21:33:12 +0000335 // If this is an alloca in the entry block, it's not a real register
336 // value.
337 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
338 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
339 continue;
340
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000341 // Avoid iterator invalidation by copying users to a temporary vector.
342 std::vector<Instruction*> Users;
343 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
344 UI != E; ++UI) {
345 Instruction *User = cast<Instruction>(*UI);
346 if (User->getParent() != BB || isa<PHINode>(User))
347 Users.push_back(User);
348 }
349
350 // Scan all of the uses and see if the live range is live across an unwind
351 // edge. If we find a use live across an invoke edge, create an alloca
352 // and spill the value.
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000353 std::set<InvokeInst*> InvokesWithStoreInserted;
354
355 // Find all of the blocks that this value is live in.
356 std::set<BasicBlock*> LiveBBs;
357 LiveBBs.insert(Inst->getParent());
358 while (!Users.empty()) {
359 Instruction *U = Users.back();
360 Users.pop_back();
361
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000362 if (!isa<PHINode>(U)) {
363 MarkBlocksLiveIn(U->getParent(), LiveBBs);
364 } else {
365 // Uses for a PHI node occur in their predecessor block.
366 PHINode *PN = cast<PHINode>(U);
367 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
368 if (PN->getIncomingValue(i) == Inst)
369 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
370 }
371 }
372
373 // Now that we know all of the blocks that this thing is live in, see if
374 // it includes any of the unwind locations.
375 bool NeedsSpill = false;
376 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
377 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
378 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
379 NeedsSpill = true;
380 }
381 }
382
383 // If we decided we need a spill, do it.
384 if (NeedsSpill) {
385 ++NumSpilled;
386 DemoteRegToStack(*Inst, true);
387 }
388 }
389}
390
391bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
392 std::vector<ReturnInst*> Returns;
393 std::vector<UnwindInst*> Unwinds;
394 std::vector<InvokeInst*> Invokes;
395
396 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
397 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
398 // Remember all return instructions in case we insert an invoke into this
399 // function.
400 Returns.push_back(RI);
401 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
402 Invokes.push_back(II);
403 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
404 Unwinds.push_back(UI);
405 }
406
407 if (Unwinds.empty() && Invokes.empty()) return false;
408
409 NumInvokes += Invokes.size();
410 NumUnwinds += Unwinds.size();
Chris Lattner5b3c7022005-09-27 22:44:59 +0000411
412 // TODO: This is not an optimal way to do this. In particular, this always
413 // inserts setjmp calls into the entries of functions with invoke instructions
414 // even though there are possibly paths through the function that do not
415 // execute any invokes. In particular, for functions with early exits, e.g.
416 // the 'addMove' method in hexxagon, it would be nice to not have to do the
417 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
418 // would not be too hard to do.
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000419
420 // If we have an invoke instruction, insert a setjmp that dominates all
421 // invokes. After the setjmp, use a cond branch that goes to the original
422 // code path on zero, and to a designated 'catch' block of nonzero.
423 Value *OldJmpBufPtr = 0;
424 if (!Invokes.empty()) {
425 // First thing we need to do is scan the whole function for values that are
426 // live across unwind edges. Each value that is live across an unwind edge
427 // we spill into a stack location, guaranteeing that there is nothing live
428 // across the unwind edge. This process also splits all critical edges
429 // coming out of invoke's.
430 splitLiveRangesLiveAcrossInvokes(Invokes);
431
432 BasicBlock *EntryBB = F.begin();
433
434 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
435 // that needs to be restored on all exits from the function. This is an
436 // alloca because the value needs to be live across invokes.
Chris Lattner97d2dbd2006-09-05 17:48:07 +0000437 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000438 AllocaInst *JmpBuf =
Chris Lattner97d2dbd2006-09-05 17:48:07 +0000439 new AllocaInst(JBLinkTy, 0, Align, "jblink", F.begin()->begin());
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000440
441 std::vector<Value*> Idx;
Reid Spencerc5b206b2006-12-31 05:48:39 +0000442 Idx.push_back(Constant::getNullValue(Type::Int32Ty));
443 Idx.push_back(ConstantInt::get(Type::Int32Ty, 1));
Chris Lattner1ccd1852007-02-12 22:56:41 +0000444 OldJmpBufPtr = new GetElementPtrInst(JmpBuf, &Idx[0], 2, "OldBuf",
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000445 EntryBB->getTerminator());
446
447 // Copy the JBListHead to the alloca.
448 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
449 EntryBB->getTerminator());
450 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
451
452 // Add the new jumpbuf to the list.
453 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
454
455 // Create the catch block. The catch block is basically a big switch
456 // statement that goes to all of the invoke catch blocks.
457 BasicBlock *CatchBB = new BasicBlock("setjmp.catch", &F);
458
459 // Create an alloca which keeps track of which invoke is currently
460 // executing. For normal calls it contains zero.
Reid Spencerc5b206b2006-12-31 05:48:39 +0000461 AllocaInst *InvokeNum = new AllocaInst(Type::Int32Ty, 0, "invokenum",
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000462 EntryBB->begin());
Reid Spencerc5b206b2006-12-31 05:48:39 +0000463 new StoreInst(ConstantInt::get(Type::Int32Ty, 0), InvokeNum, true,
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000464 EntryBB->getTerminator());
465
466 // Insert a load in the Catch block, and a switch on its value. By default,
467 // we go to a block that just does an unwind (which is the correct action
468 // for a standard call).
469 BasicBlock *UnwindBB = new BasicBlock("unwindbb", &F);
470 Unwinds.push_back(new UnwindInst(UnwindBB));
471
472 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
473 SwitchInst *CatchSwitch =
474 new SwitchInst(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
475
476 // Now that things are set up, insert the setjmp call itself.
477
478 // Split the entry block to insert the conditional branch for the setjmp.
479 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
480 "setjmp.cont");
481
Reid Spencerc5b206b2006-12-31 05:48:39 +0000482 Idx[1] = ConstantInt::get(Type::Int32Ty, 0);
Chris Lattner1ccd1852007-02-12 22:56:41 +0000483 Value *JmpBufPtr = new GetElementPtrInst(JmpBuf, &Idx[0], Idx.size(),
484 "TheJmpBuf",
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000485 EntryBB->getTerminator());
486 Value *SJRet = new CallInst(SetJmpFn, JmpBufPtr, "sjret",
487 EntryBB->getTerminator());
488
489 // Compare the return value to zero.
Reid Spencere4d87aa2006-12-23 06:05:41 +0000490 Value *IsNormal = new ICmpInst(ICmpInst::ICMP_EQ, SJRet,
491 Constant::getNullValue(SJRet->getType()),
492 "notunwind", EntryBB->getTerminator());
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000493 // Nuke the uncond branch.
494 EntryBB->getTerminator()->eraseFromParent();
495
496 // Put in a new condbranch in its place.
497 new BranchInst(ContBlock, CatchBB, IsNormal, EntryBB);
498
499 // At this point, we are all set up, rewrite each invoke instruction.
500 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
501 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch);
502 }
503
504 // We know that there is at least one unwind.
505
506 // Create three new blocks, the block to load the jmpbuf ptr and compare
507 // against null, the block to do the longjmp, and the error block for if it
508 // is null. Add them at the end of the function because they are not hot.
509 BasicBlock *UnwindHandler = new BasicBlock("dounwind", &F);
510 BasicBlock *UnwindBlock = new BasicBlock("unwind", &F);
511 BasicBlock *TermBlock = new BasicBlock("unwinderror", &F);
512
513 // If this function contains an invoke, restore the old jumpbuf ptr.
514 Value *BufPtr;
515 if (OldJmpBufPtr) {
516 // Before the return, insert a copy from the saved value to the new value.
517 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
518 new StoreInst(BufPtr, JBListHead, UnwindHandler);
519 } else {
520 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
521 }
522
523 // Load the JBList, if it's null, then there was no catch!
Reid Spencere4d87aa2006-12-23 06:05:41 +0000524 Value *NotNull = new ICmpInst(ICmpInst::ICMP_NE, BufPtr,
525 Constant::getNullValue(BufPtr->getType()),
526 "notnull", UnwindHandler);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000527 new BranchInst(UnwindBlock, TermBlock, NotNull, UnwindHandler);
528
529 // Create the block to do the longjmp.
530 // Get a pointer to the jmpbuf and longjmp.
531 std::vector<Value*> Idx;
Reid Spencerc5b206b2006-12-31 05:48:39 +0000532 Idx.push_back(Constant::getNullValue(Type::Int32Ty));
533 Idx.push_back(ConstantInt::get(Type::Int32Ty, 0));
Chris Lattner1ccd1852007-02-12 22:56:41 +0000534 Idx[0] = new GetElementPtrInst(BufPtr, &Idx[0], 2, "JmpBuf", UnwindBlock);
Reid Spencerc5b206b2006-12-31 05:48:39 +0000535 Idx[1] = ConstantInt::get(Type::Int32Ty, 1);
Chris Lattnerf4e6c3a2005-09-27 21:18:17 +0000536 new CallInst(LongJmpFn, Idx, "", UnwindBlock);
537 new UnreachableInst(UnwindBlock);
538
539 // Set up the term block ("throw without a catch").
540 new UnreachableInst(TermBlock);
541
542 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
543 writeAbortMessage(TermBlock->getTerminator());
544
545 // Insert a call to abort()
546 (new CallInst(AbortFn, std::vector<Value*>(), "",
547 TermBlock->getTerminator()))->setTailCall();
548
549
550 // Replace all unwinds with a branch to the unwind handler.
551 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
552 new BranchInst(UnwindHandler, Unwinds[i]);
553 Unwinds[i]->eraseFromParent();
554 }
555
556 // Finally, for any returns from this function, if this function contains an
557 // invoke, restore the old jmpbuf pointer to its input value.
558 if (OldJmpBufPtr) {
559 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
560 ReturnInst *R = Returns[i];
561
562 // Before the return, insert a copy from the saved value to the new value.
563 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
564 new StoreInst(OldBuf, JBListHead, true, R);
565 }
566 }
567
568 return true;
Chris Lattner6d784572004-02-08 19:53:56 +0000569}
570
571bool LowerInvoke::runOnFunction(Function &F) {
572 if (ExpensiveEHSupport)
573 return insertExpensiveEHSupport(F);
574 else
575 return insertCheapEHSupport(F);
576}