[WinEH] Don't inline an 'unwinds to caller' cleanupret into funclets which locally unwind

It is problematic if the inlinee has a cleanupret which unwinds to
caller and we inline it into a call site which doesn't unwind.

If the funclet unwinds anywhere other than to the caller,
then we will give the funclet two unwind destinations.
This will result in a verifier failure.

Seeing as how the caller wasn't an invoke (which would locally unwind)
and that the funclet cannot unwind to caller, we must conclude that an
'unwind to caller' cleanupret is dynamically unreachable.

This fixes PR26698.

Differential Revision: http://reviews.llvm.org/D17536

llvm-svn: 261656

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index db98de89183..491b18e6fc7 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1420,6 +1420,19 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
     }
   }
 
+  // Determine if we are dealing with a call in an EHPad which does not unwind
+  // to caller.
+  bool EHPadForCallUnwindsLocally = false;
+  if (CallSiteEHPad && CS.isCall()) {
+    UnwindDestMemoTy FuncletUnwindMap;
+    Value *CallSiteUnwindDestToken =
+        getUnwindDestToken(CallSiteEHPad, FuncletUnwindMap);
+
+    EHPadForCallUnwindsLocally =
+        CallSiteUnwindDestToken &&
+        !isa<ConstantTokenNone>(CallSiteUnwindDestToken);
+  }
+
   // Get an iterator to the last basic block in the function, which will have
   // the new function inlined after it.
   Function::iterator LastBlock = --Caller->end();
@@ -1763,6 +1776,14 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
         OpBundles.clear();
       }
 
+      // It is problematic if the inlinee has a cleanupret which unwinds to
+      // caller and we inline it into a call site which doesn't unwind but into
+      // an EH pad that does.  Such an edge must be dynamically unreachable.
+      // As such, we replace the cleanupret with unreachable.
+      if (auto *CleanupRet = dyn_cast<CleanupReturnInst>(BB->getTerminator()))
+        if (CleanupRet->unwindsToCaller() && EHPadForCallUnwindsLocally)
+          changeToUnreachable(CleanupRet, /*UseLLVMTrap=*/false);
+
       Instruction *I = BB->getFirstNonPHI();
       if (!I->isEHPad())
         continue;