add a new @llvm.donothing intrinsic that, well, does nothing, and teach CodeGen to ignore calls to it

llvm-svn: 159383

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 0d2d9dae2bc..957d00ac32b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1828,9 +1828,13 @@ void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
   MachineBasicBlock *LandingPad = FuncInfo.MBBMap[I.getSuccessor(1)];
 
   const Value *Callee(I.getCalledValue());
+  const Function *Fn = dyn_cast<Function>(Callee);
   if (isa<InlineAsm>(Callee))
     visitInlineAsm(&I);
-  else
+  else if (Fn && Fn->isIntrinsic()) {
+    assert(Fn->getIntrinsicID() == Intrinsic::donothing);
+    return; // ignore invokes to @llvm.donothing
+  } else
     LowerCallTo(&I, getValue(Callee), false, LandingPad);
 
   // If the value of the invoke is used outside of its defining block, make it
@@ -5178,6 +5182,9 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
   case Intrinsic::lifetime_end:
     // Discard region information.
     return 0;
+  case Intrinsic::donothing:
+    // ignore
+    return 0;
   }
 }