If a vector is empty, you're not allowed to access any

elements, even if it is only to take the address.  Test:
break-anti-dependencies.ll with ENABLE_EXPENSIVE_CHECKS.

llvm-svn: 62576

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
index 2e5d8336352..7c0e80afe43 100644
--- a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
+++ b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
@@ -49,10 +49,11 @@ namespace llvm {
     ///
     SUnit *NewSUnit(MachineInstr *MI) {
 #ifndef NDEBUG
-      const SUnit *Addr = &SUnits[0];
+      const SUnit *Addr = SUnits.empty() ? 0 : &SUnits[0];
 #endif
       SUnits.push_back(SUnit(MI, (unsigned)SUnits.size()));
-      assert(Addr == &SUnits[0] && "SUnits std::vector reallocated on the fly!");
+      assert((Addr == 0 || Addr == &SUnits[0]) &&
+             "SUnits std::vector reallocated on the fly!");
       SUnits.back().OrigNode = &SUnits.back();
       return &SUnits.back();
     }