Initial checkin of the LLVM->LLVM transform to support code generators which

do not support stack unwinding yet

llvm-svn: 8869

lib/Transforms/Scalar/LowerInvoke.cpp

@@ -0,0 +1,74 @@
+//===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
+//
+// This transformation is designed for use by code generators which do not yet
+// support stack unwinding.  This pass gives them the ability to execute any
+// program which does not throw an exception, by turning 'invoke' instructions
+// into calls and by turning 'unwind' instructions into calls to abort().
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Pass.h"
+#include "llvm/iTerminators.h"
+#include "llvm/iOther.h"
+#include "llvm/Module.h"
+#include "llvm/Type.h"
+#include "llvm/Constant.h"
+#include "Support/Statistic.h"
+
+namespace {
+  Statistic<> NumLowered("lowerinvoke", "Number of invoke & unwinds replaced");
+
+  class LowerInvoke : public FunctionPass {
+    Function *AbortFn;
+  public:
+    bool doInitialization(Module &M);
+    bool runOnFunction(Function &F);
+  };
+
+  RegisterOpt<LowerInvoke>
+  X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
+}
+
+FunctionPass *createLowerInvokePass() { return new LowerInvoke(); }
+
+// doInitialization - Make sure that there is a prototype for abort in the
+// current module.
+bool LowerInvoke::doInitialization(Module &M) {
+  AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, 0);
+  return true;
+}
+
+bool LowerInvoke::runOnFunction(Function &F) {
+  bool Changed = false;
+  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+    if (InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
+      // Insert a normal call instruction...
+      std::string Name = II->getName(); II->setName("");
+      Value *NewCall = new CallInst(II->getCalledValue(),
+                                    std::vector<Value*>(II->op_begin()+3,
+                                                        II->op_end()), Name,II);
+      II->replaceAllUsesWith(NewCall);
+      
+      // Insert an unconditional branch to the normal destination
+      new BranchInst(II->getNormalDest(), II);
+
+      // Remove the invoke instruction now.
+      I->getInstList().erase(II);
+
+      ++NumLowered; Changed = true;
+    } else if (UnwindInst *UI = dyn_cast<UnwindInst>(I->getTerminator())) {
+      // Insert a call to abort()
+      new CallInst(AbortFn, std::vector<Value*>(), "", UI);
+
+      // Insert a return instruction.
+      new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 :
+                            Constant::getNullValue(F.getReturnType()), UI);
+
+      // Remove the unwind instruction now.
+      I->getInstList().erase(UI);
+
+      ++NumLowered; Changed = true;
+    }
+  return Changed;
+}