diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index b74c99adf..085ab3fa8 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -1131,7 +1131,16 @@ namespace Eigen {
       #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+r,v,wa" (X));
     #elif EIGEN_ARCH_ARM_OR_ARM64
       // General, NEON.
-      #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+r,w" (X));
+      // Clang doesn't like "r",
+      //    error: non-trivial scalar-to-vector conversion, possible invalid
+      //           constraint for vector type
+      // GCC < 5 doesn't like "g",
+      //    error: 'asm' operand requires impossible reload
+      #if EIGEN_COMP_GNUC_STRICT && EIGEN_GNUC_AT_MOST(5, 0)
+        #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+r,w" (X));
+      #else
+        #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g,w" (X));
+      #endif
     #elif EIGEN_ARCH_i386_OR_x86_64
       // General, SSE.
       #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g,x" (X));