[Attributor][Fix] Make sure we do not delete live code

Summary: Liveness needs to mark edges, not blocks as dead.

Reviewers: sstefan1, uenoku

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67191

llvm-svn: 370975

1 files changed, 14 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index 04b9c5f8ced..672968f8302 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1883,8 +1883,20 @@ struct AAIsDeadImpl : public AAIsDead {
           }
         }
 
-        if (SplitPos == &NormalDestBB->front())
-          assumeLive(A, *NormalDestBB);
+        if (SplitPos == &NormalDestBB->front()) {
+          // If this is an invoke of a noreturn function the edge to the normal
+          // destination block is dead but not necessarily the block itself.
+          // TODO: We need to move to an edge based system during deduction and
+          //       also manifest.
+          assert(!NormalDestBB->isLandingPad() &&
+                 "Expected the normal destination not to be a landingpad!");
+          BasicBlock *SplitBB =
+              SplitBlockPredecessors(NormalDestBB, {BB}, ".dead");
+          // The split block is live even if it contains only an unreachable
+          // instruction at the end.
+          assumeLive(A, *SplitBB);
+          SplitPos = SplitBB->getTerminator();
+        }
       }
 
       BB = SplitPos->getParent();