Fix assertion in jump threading (PR13405).

GetBestDestForJumpOnUndef() assumes there is at least 1 successor, which isn't
true if the block ends in an indirect branch with no successors. Fix this by
bailing out earlier in this case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160546 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 429b61b6e50111a7f08d14726cf54d1ace408aaa..6b8430f02830a45b27cf0355d1f0f7900d594c40 100644 (file)
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -670,6 +670,8 @@ bool JumpThreading::ProcessBlock(BasicBlock *BB) {
   } else if (SwitchInst *SI = dyn_cast<SwitchInst>(Terminator)) {
     Condition = SI->getCondition();
   } else if (IndirectBrInst *IB = dyn_cast<IndirectBrInst>(Terminator)) {
+    // Can't thread indirect branch with no successors.
+    if (IB->getNumSuccessors() == 0) return false;
     Condition = IB->getAddress()->stripPointerCasts();
     Preference = WantBlockAddress;
   } else {

diff --git a/test/Transforms/JumpThreading/2012-07-19-NoSuccessorIndirectBr.ll b/test/Transforms/JumpThreading/2012-07-19-NoSuccessorIndirectBr.ll
new file mode 100644 (file)
index 0000000..1c2c0c7
--- /dev/null
+++ b/test/Transforms/JumpThreading/2012-07-19-NoSuccessorIndirectBr.ll
@@ -0,0 +1,8 @@
+; RUN: opt < %s -jump-threading
+; PR 13405
+; Just check that it doesn't crash / assert
+
+define i32 @f() nounwind {
+entry:
+  indirectbr i8* undef, []
+}