Added a test and fixed a bug in BumpPtrAllocator relating to large alignment
values.  Hopefully this fixes PR4622.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77088 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Allocator.cpp b/lib/Support/Allocator.cpp
index 230c421..36da443 100644
--- a/lib/Support/Allocator.cpp
+++ b/lib/Support/Allocator.cpp
@@ -95,8 +95,8 @@
   }
 
   // If Size is really big, allocate a separate slab for it.
-  if (Size > SizeThreshold) {
-    size_t PaddedSize = Size + sizeof(MemSlab) + Alignment - 1;
+  size_t PaddedSize = Size + sizeof(MemSlab) + Alignment - 1;
+  if (PaddedSize > SizeThreshold) {
     MemSlab *NewSlab = Allocator.Allocate(PaddedSize);
 
     // Put the new slab after the current slab, since we are not allocating