Work around GCC bug in constexpr to attributes

src/IceDefs.h

 //===- subzero/src/IceDefs.h - Common Subzero declaraions -------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares various useful types and classes that have
@@ skipping 111 matching lines @@
 
 typedef uint32_t TimerStackIdT;
 typedef uint32_t TimerIdT;
 
 // Use alignas(MaxCacheLineSize) to isolate variables/fields that
 // might be contended while multithreading.  Assumes the maximum cache
 // line size is 64.
 enum { MaxCacheLineSize = 64 };
 // Use ICE_CACHELINE_BOUNDARY to force the next field in a declaration
 // list to be aligned to the next cache line.
+// Note: zero is added to work around the following GCC 4.8 bug (fixed in 4.9):
+//       https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55382
 #define ICE_CACHELINE_BOUNDARY                                                 \
-  __attribute__((aligned(MaxCacheLineSize))) int : 0
+  __attribute__((aligned(MaxCacheLineSize + 0))) int : 0
 
 // PNaCl is ILP32, so theoretically we should only need 32-bit offsets.
 typedef int32_t RelocOffsetT;
 enum { RelocAddrSize = 4 };
 
 enum LivenessMode {
   // Basic version of live-range-end calculation.  Marks the last uses
   // of variables based on dataflow analysis.  Records the set of
   // live-in and live-out variables for each block.  Identifies and
   // deletes dead instructions (primarily stores).
@@ skipping 64 matching lines @@
   return llvm::make_range(Container.rbegin(), Container.rend());
 }
 template <typename T>
 llvm::iterator_range<typename T::reverse_iterator> reverse_range(T &Container) {
   return llvm::make_range(Container.rbegin(), Container.rend());
 }
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEDEFS_H