InstCombine: Don't strip bitcasts off of callsites marked 'thunk'

The return type of a thunk is meaningless, we just want the arguments
and return value to be forwarded.

llvm-svn: 226708

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 40f288c175c..0223d69ab57 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1381,6 +1381,10 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
     dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts());
   if (!Callee)
     return false;
+  // The prototype of thunks are a lie, don't try to directly call such
+  // functions.
+  if (Callee->hasFnAttribute("thunk"))
+    return false;
   Instruction *Caller = CS.getInstruction();
   const AttributeSet &CallerPAL = CS.getAttributes();