Use the fast register allocator by default for -O0 builds.

This affects both llvm-gcc and clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105372 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index 09123fe..3489db2 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -61,7 +61,7 @@
   // When the 'default' allocator is requested, pick one based on OptLevel.
   switch (OptLevel) {
   case CodeGenOpt::None:
-    return createLocalRegisterAllocator();
+    return createFastRegisterAllocator();
   default:
     return createLinearScanRegisterAllocator();
   }