Subzero: Allow deeper levels of variable splitting.

src/IceInst.cpp

Index: src/IceInst.cpp
diff --git a/src/IceInst.cpp b/src/IceInst.cpp
index f9cfdddf60c13b41771fd4a9fa80dd6d46edd2db..3a07b52e4f97a755a6249f0ac1e1691332483941 100644
--- a/src/IceInst.cpp
+++ b/src/IceInst.cpp
@@ -1094,9 +1094,15 @@ bool checkForRedundantAssign(const Variable *Dest, const Operand *Source) {
     // upper 32 bits of rax. We need to recognize and preserve these.
     return true;
   }
-  if (!Dest->hasReg() && !SrcVar->hasReg() &&
-      Dest->getStackOffset() == SrcVar->getStackOffset())
+  if (!Dest->hasReg() && !SrcVar->hasReg()) {
+    if (!Dest->hasStackOffset() || !SrcVar->hasStackOffset()) {
+      return false;
+    }
+    if (Dest->getStackOffset() != SrcVar->getStackOffset()) {
+      return false;
+    }
     return true;
+  }
   return false;
 }