Allow null-valued function operands in getCalledFunction()

Summary:
Change the dynamic cast in CallBase::getCalledFunction() to allow
null-valued function operands.

This patch fixes a crash that occurred when a funtion operand of a
call instruction was dropped, and later on a metadata-carrying
instruction was printed out. When allocating the metadata slot numbers,
getCalledFunction() would be invoked on the call with the dropped
operand, resulting in a failed non-null assertion in isa<>.

This fixes PR38924, in which a printout in DBCE crashed due to this.

This aligns getCalledFunction() with getCalledValue(), as the latter
allows the operand to be null.

Reviewers: vsk, dexonsmith, hfinkel

Reviewed By: dexonsmith

Subscribers: hfinkel, llvm-commits

Differential Revision: https://reviews.llvm.org/D52537

llvm-svn: 345966

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/unittests/IR/MetadataTest.cpp b/llvm/unittests/IR/MetadataTest.cpp
index 83b166a263c..100c4ed5e15 100644
--- a/llvm/unittests/IR/MetadataTest.cpp
+++ b/llvm/unittests/IR/MetadataTest.cpp
@@ -402,6 +402,27 @@ TEST_F(MDNodeTest, PrintFromMetadataAsValue) {
   EXPECT_PRINTER_EQ("metadata !0", MAV0->printAsOperand(OS, true, MST));
   EXPECT_PRINTER_EQ("metadata !1", MAV1->printAsOperand(OS, true, MST));
 }
+
+TEST_F(MDNodeTest, PrintWithDroppedCallOperand) {
+  Module M("test", Context);
+
+  auto *FTy = FunctionType::get(Type::getVoidTy(Context), false);
+  auto *F0 = Function::Create(FTy, GlobalValue::ExternalLinkage, "F0", &M);
+  auto *F1 = Function::Create(FTy, GlobalValue::ExternalLinkage, "F1", &M);
+  auto *BB0 = BasicBlock::Create(Context, "entry", F0);
+
+  CallInst *CI0 = CallInst::Create(F1, "", BB0);
+  CI0->dropAllReferences();
+
+  auto *R0 = ReturnInst::Create(Context, BB0);
+  auto *N0 = MDNode::getDistinct(Context, None);
+  R0->setMetadata("md", N0);
+
+  // Printing the metadata node would previously result in a failed assertion
+  // due to the call instruction's dropped function operand.
+  ModuleSlotTracker MST(&M);
+  EXPECT_PRINTER_EQ("!0 = distinct !{}", N0->print(OS, MST));
+}
 #undef EXPECT_PRINTER_EQ
 
 TEST_F(MDNodeTest, NullOperand) {