[llvm] r268001 - DivergenceAnalysis: Fix crash with unreachable blocks

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Fri Apr 29 01:17:47 2016
New Revision: 268001

URL: http://llvm.org/viewvc/llvm-project?rev=268001&view=rev
Log:
DivergenceAnalysis: Fix crash with unreachable blocks

Unreachable blocks may not be in the dominator tree,
so don't crash on them.

Added:
    llvm/trunk/test/Analysis/DivergenceAnalysis/AMDGPU/unreachable-loop-block.ll
Modified:
    llvm/trunk/lib/Analysis/DivergenceAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/DivergenceAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/DivergenceAnalysis.cpp?rev=268001&r1=268000&r2=268001&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/DivergenceAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/DivergenceAnalysis.cpp Fri Apr 29 01:17:47 2016
@@ -138,6 +138,11 @@ void DivergencePropagator::exploreSyncDe
   //   a2 = 2;
   // a = phi(a1, a2); // sync dependent on (tid < 5)
   BasicBlock *ThisBB = TI->getParent();
+
+  // Unreachable blocks may not be in the dominator tree.
+  if (!DT.isReachableFromEntry(ThisBB))
+    return;
+
   BasicBlock *IPostDom = PDT.getNode(ThisBB)->getIDom()->getBlock();
   if (IPostDom == nullptr)
     return;

Added: llvm/trunk/test/Analysis/DivergenceAnalysis/AMDGPU/unreachable-loop-block.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/DivergenceAnalysis/AMDGPU/unreachable-loop-block.ll?rev=268001&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/DivergenceAnalysis/AMDGPU/unreachable-loop-block.ll (added)
+++ llvm/trunk/test/Analysis/DivergenceAnalysis/AMDGPU/unreachable-loop-block.ll Fri Apr 29 01:17:47 2016
@@ -0,0 +1,17 @@
+; RUN: opt %s -mtriple amdgcn-- -analyze -divergence | FileCheck %s
+
+; CHECK: DIVERGENT:  %tmp = cmpxchg volatile
+define void @unreachable_loop(i32 %tidx) #0 {
+entry:
+  unreachable
+
+unreachable_loop:                                        ; preds = %do.body.i, %if.then11
+  %tmp = cmpxchg volatile i32 addrspace(1)* null, i32 0, i32 0 seq_cst seq_cst
+  %cmp.i = extractvalue { i32, i1 } %tmp, 1
+  br i1 %cmp.i, label %unreachable_loop, label %end
+
+end:                                      ; preds = %do.body.i51, %atomicAdd_g_f.exit
+  unreachable
+}
+
+attributes #0 = { norecurse nounwind }