Fix typo that somehow escaped both testing and code inspection.

llvm-svn: 166475
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 390b63c..7f8c3ae 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -965,7 +965,7 @@
         continue;
       }
 
-      if (Cast->getOperand(0)) {
+      if (Cast->getOpcode() == Instruction::Trunc) {
         // Op is truncated from a larger type, descale in the larger type.
         // Suppose Op = trunc X, and we descale X as Y * sext Scale.  Then
         //   trunc (Y * sext Scale) = (trunc Y) * Scale