Remove Emscripten support

lib/Transforms/NaCl/LowerEmSetjmp.cpp

-//===- LowerEmSetjmp - Lower setjmp/longjmp for Emscripten/JS   -----------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// Lowers setjmp to a reasonably-performant approach for emscripten. The idea
-// is that each block with a setjmp is broken up into the part right after
-// the setjmp, and a new basic block is added which is either reached from
-// the setjmp, or later from a longjmp. To handle the longjmp, all calls that
-// might longjmp are checked immediately afterwards.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DerivedTypes.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Target/TargetLowering.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Transforms/NaCl.h"
-#include "llvm/IR/Dominators.h"
-#include "llvm/Transforms/Utils/PromoteMemToReg.h"
-#include <vector>
-#include <set>
-#include <list>
-
-#include "llvm/Support/raw_ostream.h"
-
-#ifdef NDEBUG
-#undef assert
-#define assert(x) { if (!(x)) report_fatal_error(#x); }
-#endif
-
-using namespace llvm;
-
-// Utilities for mem/reg: based on Reg2Mem and MemToReg
-
-bool valueEscapes(const Instruction *Inst) {
-  const BasicBlock *BB = Inst->getParent();
-  for (Value::const_user_iterator UI = Inst->user_begin(),E = Inst->user_end();
-       UI != E; ++UI) {
-    const User *U = *UI;
-    const Instruction *I = cast<Instruction>(U);
-    if (I->getParent() != BB || isa<PHINode>(I))
-      return true;
-  }
-  return false;
-}
-
-void doRegToMem(Function &F) { // see Reg2Mem.cpp
-  // Insert all new allocas into entry block.
-  BasicBlock *BBEntry = &F.getEntryBlock();
-  assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
-         "Entry block to function must not have predecessors!");
-
-  // Find first non-alloca instruction and create insertion point. This is
-  // safe if block is well-formed: it always have terminator, otherwise
-  // we'll get and assertion.
-  BasicBlock::iterator I = BBEntry->begin();
-  while (isa<AllocaInst>(I)) ++I;
-
-  CastInst *AllocaInsertionPoint =
-    new BitCastInst(Constant::getNullValue(Type::getInt32Ty(F.getContext())),
-                    Type::getInt32Ty(F.getContext()),
-                    "reg2mem alloca point", I);
-
-  // Find the escaped instructions. But don't create stack slots for
-  // allocas in entry block.
-  std::list<Instruction*> WorkList;
-  for (Function::iterator ibb = F.begin(), ibe = F.end();
-       ibb != ibe; ++ibb)
-    for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
-         iib != iie; ++iib) {
-      if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
-          valueEscapes(iib)) {
-        WorkList.push_front(&*iib);
-      }
-    }
-
-  // Demote escaped instructions
-  for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
-       ile = WorkList.end(); ilb != ile; ++ilb)
-    DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
-
-  WorkList.clear();
-
-  // Find all phi's
-  for (Function::iterator ibb = F.begin(), ibe = F.end();
-       ibb != ibe; ++ibb)
-    for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
-         iib != iie; ++iib)
-      if (isa<PHINode>(iib))
-        WorkList.push_front(&*iib);
-
-  // Demote phi nodes
-  for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
-       ile = WorkList.end(); ilb != ile; ++ilb)
-    DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
-}
-
-void doMemToReg(Function &F) {
-  std::vector<AllocaInst*> Allocas;
-
-  BasicBlock &BB = F.getEntryBlock();  // Get the entry node for the function
-
-  DominatorTreeWrapperPass DTW;
-  DTW.runOnFunction(F);
-  DominatorTree& DT = DTW.getDomTree();
-
-  while (1) {
-    Allocas.clear();
-
-    // Find allocas that are safe to promote, by looking at all instructions in
-    // the entry node
-    for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
-      if (AllocaInst *AI = dyn_cast<AllocaInst>(I))       // Is it an alloca?
-        if (isAllocaPromotable(AI))
-          Allocas.push_back(AI);
-
-    if (Allocas.empty()) break;
-
-    PromoteMemToReg(Allocas, DT);
-  }
-}
-
-// LowerEmSetjmp
-
-namespace {
-  class LowerEmSetjmp : public ModulePass {
-    Module *TheModule;
-
-  public:
-    static char ID; // Pass identification, replacement for typeid
-    explicit LowerEmSetjmp() : ModulePass(ID), TheModule(NULL) {
-      initializeLowerEmSetjmpPass(*PassRegistry::getPassRegistry());
-    }
-    bool runOnModule(Module &M);
-  };
-}
-
-char LowerEmSetjmp::ID = 0;
-INITIALIZE_PASS(LowerEmSetjmp, "loweremsetjmp",
-                "Lower setjmp and longjmp for js/emscripten",
-                false, false)
-
-bool LowerEmSetjmp::runOnModule(Module &M) {
-  TheModule = &M;
-
-  Function *Setjmp = TheModule->getFunction("setjmp");
-  Function *Longjmp = TheModule->getFunction("longjmp");
-  if (!Setjmp && !Longjmp) return false;
-
-  Type *i32 = Type::getInt32Ty(M.getContext());
-  Type *Void = Type::getVoidTy(M.getContext());
-
-  // Add functions
-
-  Function *EmSetjmp = NULL;
-
-  if (Setjmp) {
-    SmallVector<Type*, 2> EmSetjmpTypes;
-    EmSetjmpTypes.push_back(Setjmp->getFunctionType()->getParamType(0));
-    EmSetjmpTypes.push_back(i32); // extra param that says which setjmp in the function it is
-    FunctionType *EmSetjmpFunc = FunctionType::get(i32, EmSetjmpTypes, false);
-    EmSetjmp = Function::Create(EmSetjmpFunc, GlobalValue::ExternalLinkage, "emscripten_setjmp", TheModule);
-  }
-
-  Function *EmLongjmp = Longjmp ? Function::Create(Longjmp->getFunctionType(), GlobalValue::ExternalLinkage, "emscripten_longjmp", TheModule) : NULL;
-
-  SmallVector<Type*, 1> IntArgTypes;
-  IntArgTypes.push_back(i32);
-  FunctionType *IntIntFunc = FunctionType::get(i32, IntArgTypes, false);
-
-  Function *CheckLongjmp = Function::Create(IntIntFunc, GlobalValue::ExternalLinkage, "emscripten_check_longjmp", TheModule); // gets control flow
-
-  Function *GetLongjmpResult = Function::Create(IntIntFunc, GlobalValue::ExternalLinkage, "emscripten_get_longjmp_result", TheModule); // gets int value longjmp'd
-
-  FunctionType *VoidFunc = FunctionType::get(Void, false);
-  Function *PrepSetjmp = Function::Create(VoidFunc, GlobalValue::ExternalLinkage, "emscripten_prep_setjmp", TheModule);
-
-  Function *CleanupSetjmp = Function::Create(VoidFunc, GlobalValue::ExternalLinkage, "emscripten_cleanup_setjmp", TheModule);
-
-  Function *PreInvoke = TheModule->getFunction("emscripten_preinvoke");
-  if (!PreInvoke) PreInvoke = Function::Create(VoidFunc, GlobalValue::ExternalLinkage, "emscripten_preinvoke", TheModule);
-
-  FunctionType *IntFunc = FunctionType::get(i32, false);
-  Function *PostInvoke = TheModule->getFunction("emscripten_postinvoke");
-  if (!PostInvoke) PostInvoke = Function::Create(IntFunc, GlobalValue::ExternalLinkage, "emscripten_postinvoke", TheModule);
-
-  // Process all callers of setjmp and longjmp. Start with setjmp.
-
-  typedef std::vector<PHINode*> Phis;
-  typedef std::map<Function*, Phis> FunctionPhisMap;
-  FunctionPhisMap SetjmpOutputPhis;
-  std::vector<Instruction*> ToErase;
-
-  if (Setjmp) {
-    for (Instruction::user_iterator UI = Setjmp->user_begin(), UE = Setjmp->user_end(); UI != UE; ++UI) {
-      User *U = *UI;
-      if (CallInst *CI = dyn_cast<CallInst>(U)) {
-        BasicBlock *SJBB = CI->getParent();
-        // The tail is everything right after the call, and will be reached once when setjmp is
-        // called, and later when longjmp returns to the setjmp
-        BasicBlock *Tail = SplitBlock(SJBB, CI->getNextNode());
-        // Add a phi to the tail, which will be the output of setjmp, which indicates if this is the
-        // first call or a longjmp back. The phi directly uses the right value based on where we
-        // arrive from
-        PHINode *SetjmpOutput = PHINode::Create(i32, 2, "", Tail->getFirstNonPHI());
-        SetjmpOutput->addIncoming(ConstantInt::get(i32, 0), SJBB); // setjmp initial call returns 0
-        CI->replaceAllUsesWith(SetjmpOutput); // The proper output is now this, not the setjmp call itself
-        // longjmp returns to the setjmp will add themselves to this phi
-        Phis& P = SetjmpOutputPhis[SJBB->getParent()];
-        P.push_back(SetjmpOutput);
-        // fix call target
-        SmallVector<Value *, 2> Args;
-        Args.push_back(CI->getArgOperand(0));
-        Args.push_back(ConstantInt::get(i32, P.size())); // our index in the function is our place in the array + 1
-        CallInst::Create(EmSetjmp, Args, "", CI);
-        ToErase.push_back(CI);
-      } else {
-        errs() << **UI << "\n";
-        report_fatal_error("bad use of setjmp, should only call it");
-      }
-    }
-  }
-
-  // Update longjmp FIXME: we could avoid throwing in longjmp as an optimization when longjmping back into the current function perhaps?
-
-  if (Longjmp) Longjmp->replaceAllUsesWith(EmLongjmp);
-
-  // Update all setjmping functions
-
-  for (FunctionPhisMap::iterator I = SetjmpOutputPhis.begin(); I != SetjmpOutputPhis.end(); I++) {
-    Function *F = I->first;
-    Phis& P = I->second;
-
-    CallInst::Create(PrepSetjmp, "", F->begin()->begin());
-
-    // Update each call that can longjmp so it can return to a setjmp where relevant
-
-    for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ) {
-      BasicBlock *BB = BBI++;
-      for (BasicBlock::iterator Iter = BB->begin(), E = BB->end(); Iter != E; ) {
-        Instruction *I = Iter++;
-        CallInst *CI;
-        if ((CI = dyn_cast<CallInst>(I))) {
-          Value *V = CI->getCalledValue();
-          if (V == PrepSetjmp || V == EmSetjmp || V == CheckLongjmp || V == GetLongjmpResult || V == PreInvoke || V == PostInvoke) continue;
-          if (Function *CF = dyn_cast<Function>(V)) if (CF->isIntrinsic()) continue;
-          // TODO: proper analysis of what can actually longjmp. Currently we assume anything but setjmp can.
-          // This may longjmp, so we need to check if it did. Split at that point, and
-          // envelop the call in pre/post invoke, if we need to
-          CallInst *After;
-          Instruction *Check = NULL;
-          if (Iter != E && (After = dyn_cast<CallInst>(Iter)) && After->getCalledValue() == PostInvoke) {
-            // use the pre|postinvoke that exceptions lowering already made
-            Check = Iter++;
-          }
-          BasicBlock *Tail = SplitBlock(BB, Iter); // Iter already points to the next instruction, as we need
-          TerminatorInst *TI = BB->getTerminator();
-          if (!Check) {
-            // no existing pre|postinvoke, create our own
-            CallInst::Create(PreInvoke, "", CI);
-            Check = CallInst::Create(PostInvoke, "", TI); // CI is at the end of the block
-
-            // If we are calling a function that is noreturn, we must remove that attribute. The code we
-            // insert here does expect it to return, after we catch the exception.
-            if (CI->doesNotReturn()) {
-              if (Function *F = dyn_cast<Function>(CI->getCalledValue())) {
-                F->removeFnAttr(Attribute::NoReturn);
-              }
-              CI->setAttributes(CI->getAttributes().removeAttribute(TheModule->getContext(), AttributeSet::FunctionIndex, Attribute::NoReturn));
-              assert(!CI->doesNotReturn());
-            }
-          }
-
-          // We need to replace the terminator in Tail - SplitBlock makes BB go straight to Tail, we need to check if a longjmp occurred, and
-          // go to the right setjmp-tail if so
-          SmallVector<Value *, 1> Args;
-          Args.push_back(Check);
-          Instruction *LongjmpCheck = CallInst::Create(CheckLongjmp, Args, "", BB);
-          Instruction *LongjmpResult = CallInst::Create(GetLongjmpResult, Args, "", BB);
-          SwitchInst *SI = SwitchInst::Create(LongjmpCheck, Tail, 2, BB);
-          // -1 means no longjmp happened, continue normally (will hit the default switch case). 0 means a longjmp that is not ours to handle, needs a rethrow. Otherwise
-          // the index mean is the same as the index in P+1 (to avoid 0).
-          for (unsigned i = 0; i < P.size(); i++) {
-            SI->addCase(cast<ConstantInt>(ConstantInt::get(i32, i+1)), P[i]->getParent());
-            P[i]->addIncoming(LongjmpResult, BB);
-          }
-          ToErase.push_back(TI); // new terminator is now the switch
-
-          // we are splitting the block here, and must continue to find other calls in the block - which is now split. so continue
-          // to traverse in the Tail
-          BB = Tail;
-          Iter = BB->begin();
-          E = BB->end();
-        } else if (InvokeInst *CI = dyn_cast<InvokeInst>(I)) { // XXX check if target is setjmp
-          (void)CI;
-          report_fatal_error("TODO: invoke inside setjmping functions");
-        }
-      }
-    }
-
-    // add a cleanup before each return
-    for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ) {
-      BasicBlock *BB = BBI++;
-      TerminatorInst *TI = BB->getTerminator();
-      if (isa<ReturnInst>(TI)) {
-        CallInst::Create(CleanupSetjmp, "", TI);
-      }
-    }
-  }
-
-  for (unsigned i = 0; i < ToErase.size(); i++) {
-    ToErase[i]->eraseFromParent();
-  }
-
-  // Finally, our modifications to the cfg can break dominance of SSA variables. For example,
-  //   if (x()) { .. setjmp() .. }
-  //   if (y()) { .. longjmp() .. }
-  // We must split the longjmp block, and it can jump into the setjmp one. But that means that when
-  // we split the setjmp block, it's first part no longer dominates its second part - there is
-  // a theoretically possible control flow path where x() is false, then y() is true and we
-  // reach the second part of the setjmp block, without ever reaching the first part. So,
-  // we recalculate regs vs. mem
-  for (FunctionPhisMap::iterator I = SetjmpOutputPhis.begin(); I != SetjmpOutputPhis.end(); I++) {
-    Function *F = I->first;
-    doRegToMem(*F);
-    doMemToReg(*F);
-  }
-
-  return true;
-}
-
-ModulePass *llvm::createLowerEmSetjmpPass() {
-  return new LowerEmSetjmp();
-}