improve optimization of invoke instructions:

 - simplifycfg:  invoke undef/null -> unreachable
 - instcombine:  invoke new  -> invoke expect(0, 0)  (an arbitrary NOOP intrinsic;  only done if the allocated memory is unused, of course)
 - verifier:  allow invoke of intrinsics  (to make the previous step work)

llvm-svn: 159146

3 files changed, 17 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 269ea1516ff..07793ac6b5f 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1169,7 +1169,14 @@ Instruction *InstCombiner::visitMalloc(Instruction &MI) {
     }
 
     if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
-      BranchInst::Create(II->getNormalDest(), II->getParent());
+      // Replace invoke with a NOOP intrinsic to maintain the original CFG
+      Module *M = II->getParent()->getParent()->getParent();
+      IntegerType *Ty = IntegerType::get(II->getContext(), 8);
+      ConstantInt *CI = ConstantInt::get(Ty, 0);
+      Value *Args[] = {CI, CI};
+      Function *F = Intrinsic::getDeclaration(M, Intrinsic::expect, Ty);
+      InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), Args,
+                         "dummy", II->getParent());
     }
     return EraseInstFromFunction(MI);
   }
diff --git a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index a66b3e38258..594369780ac 100644
--- a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -157,11 +157,16 @@ static bool MarkAliveBlocks(BasicBlock *BB,
     }
 
     // Turn invokes that call 'nounwind' functions into ordinary calls.
-    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
-      if (II->doesNotThrow()) {
+    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+      Value *Callee = II->getCalledValue();
+      if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
+        ChangeToUnreachable(II, true);
+        Changed = true;
+      } else if (II->doesNotThrow()) {
         ChangeToCall(II);
         Changed = true;
       }
+    }
 
     Changed |= ConstantFoldTerminator(BB, true);
     for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
diff --git a/llvm/lib/VMCore/Verifier.cpp b/llvm/lib/VMCore/Verifier.cpp
index 477b81dc67f..9a9b0b7e0b3 100644
--- a/llvm/lib/VMCore/Verifier.cpp
+++ b/llvm/lib/VMCore/Verifier.cpp
@@ -1636,7 +1636,8 @@ void Verifier::visitInstruction(Instruction &I) {
     if (Function *F = dyn_cast<Function>(I.getOperand(i))) {
       // Check to make sure that the "address of" an intrinsic function is never
       // taken.
-      Assert1(!F->isIntrinsic() || (i + 1 == e && isa<CallInst>(I)),
+      CallSite CS(&I);
+      Assert1(!F->isIntrinsic() || (CS && i == (CS.isCall() ? e-1 : 2)),
               "Cannot take the address of an intrinsic!", &I);
       Assert1(F->getParent() == Mod, "Referencing function in another module!",
               &I);