Disable PRE for now. It seems to be breaking llvm-gcc bootstrapping.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52518 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 88377d5..a0ba739 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -42,7 +42,7 @@
 STATISTIC(NumGVNLoad, "Number of loads deleted");
 STATISTIC(NumGVNPRE, "Number of instructions PRE'd");
 
-static cl::opt<bool> DisablePRE("disable-pre",
+static cl::opt<bool> EnablePRE("enable-pre",
                                 cl::init(false), cl::Hidden);
 
 //===----------------------------------------------------------------------===//
@@ -1290,7 +1290,7 @@
        DE = df_end(DT.getRootNode()); DI != DE; ++DI)
     changed |= processBlock(*DI);
   
-  if (!DisablePRE)
+  if (!EnablePRE)
     changed |= performPRE(F);
   
   return changed;