EscapeAnalysis: handle SILUndef values

fixes a crash

rdar://problem/50279857

Author: eeckstein

lib/SILOptimizer/Analysis/EscapeAnalysis.cpp

@@ -1070,6 +1070,11 @@ static bool mayContainReference(SILType Ty, const SILFunction &F) {
 
 bool EscapeAnalysis::isPointer(ValueBase *V) {
   auto *F = V->getFunction();
+
+  // The function can be null, e.g. if V is an undef.
+  if (!F)
+    return false;
+
   SILType Ty = V->getType();
   auto Iter = isPointerCache.find(Ty);
   if (Iter != isPointerCache.end())

test/SILOptimizer/escape_analysis.sil

@@ -74,6 +74,24 @@ struct FourFields {
   let d : Y
 }
 
+sil @take_indirect_tuple : $@convention(method) (@in (Int, ())) -> ()
+
+// CHECK-LABEL: CG of handle_undef
+// CHECK:         Val %2 Esc: G, Succ: (%2.1)
+// CHECK:         Con %2.1 Esc: G, Succ: 
+// CHECK:       End
+sil @handle_undef : $@convention(thin) (Int) -> () {
+bb0(%0 : $Int):
+  %1 = tuple $(Int, ()) (%0, undef)
+  %5 = alloc_stack $(Int, ())
+  store %1 to %5 : $*(Int, ())
+  %7 = function_ref @take_indirect_tuple : $@convention(method) (@in (Int, ())) -> ()
+  %8 = apply %7(%5) : $@convention(method) (@in (Int, ())) -> ()
+  dealloc_stack %5 : $*(Int, ())
+  %10 = tuple ()
+  return %10 : $()
+}
+
 // Sanity check with a simple function.
 
 // CHECK-LABEL: CG of test_simple