[llvm] r321567 - IR: Fix BasicBlock::phis for empty blocks

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Fri Dec 29 11:25:53 2017
New Revision: 321567

URL: http://llvm.org/viewvc/llvm-project?rev=321567&view=rev
Log:
IR: Fix BasicBlock::phis for empty blocks

Modified:
    llvm/trunk/lib/IR/BasicBlock.cpp
    llvm/trunk/unittests/IR/BasicBlockTest.cpp

Modified: llvm/trunk/lib/IR/BasicBlock.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/BasicBlock.cpp?rev=321567&r1=321566&r2=321567&view=diff
==============================================================================
--- llvm/trunk/lib/IR/BasicBlock.cpp (original)
+++ llvm/trunk/lib/IR/BasicBlock.cpp Fri Dec 29 11:25:53 2017
@@ -264,7 +264,8 @@ const BasicBlock *BasicBlock::getUniqueS
 }
 
 iterator_range<BasicBlock::phi_iterator> BasicBlock::phis() {
-  return make_range<phi_iterator>(dyn_cast<PHINode>(&front()), nullptr);
+  PHINode *P = empty() ? nullptr : dyn_cast<PHINode>(&*begin());
+  return make_range<phi_iterator>(P, nullptr);
 }
 
 /// This method is used to notify a BasicBlock that the

Modified: llvm/trunk/unittests/IR/BasicBlockTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/BasicBlockTest.cpp?rev=321567&r1=321566&r2=321567&view=diff
==============================================================================
--- llvm/trunk/unittests/IR/BasicBlockTest.cpp (original)
+++ llvm/trunk/unittests/IR/BasicBlockTest.cpp Fri Dec 29 11:25:53 2017
@@ -33,6 +33,12 @@ TEST(BasicBlockTest, PhiRange) {
   std::unique_ptr<BasicBlock> BB2(BasicBlock::Create(Context));
   BranchInst::Create(BB.get(), BB2.get());
 
+  // Make sure this doesn't crash if there are no phis.
+  for (auto &PN : BB->phis()) {
+    (void)PN;
+    EXPECT_TRUE(false) << "empty block should have no phis";
+  }
+
   // Make it a cycle.
   auto *BI = BranchInst::Create(BB.get(), BB.get());