Fix unaligned access problems empirically observed on ARM 7 chipsets.

https://code.google.com/p/cld2/issues/detail?id=11



git-svn-id: https://cld2.googlecode.com/svn/trunk@159 b252ecd4-b096-bf77-eb8e-91563289f87e

internal/port.h

@@ -52,7 +52,11 @@ namespace CLD2 {
       !defined(__ARM_ARCH_6K__) && \
       !defined(__ARM_ARCH_6Z__) && \
       !defined(__ARM_ARCH_6ZK__) && \
-      !defined(__ARM_ARCH_6T2__)
+      !defined(__ARM_ARCH_6T2__) && \
+      !defined(__ARM_ARCH_7__) && \
+      !defined(__ARM_ARCH_7A__) && \
+      !defined(__ARM_ARCH_7M__) && \
+      !defined(__ARM_ARCH_7R__)
 
 // ARMv7 and newer support native unaligned accesses, but only of 16-bit
 // and 32-bit values (not 64-bit); older versions either raise a fatal signal,
@@ -62,6 +66,12 @@ namespace CLD2 {
 // sub-architectures. Newer gcc (>= 4.6) set an __ARM_FEATURE_ALIGNED #define,
 // so in time, maybe we can move on to that.
 //
+// Note that even if a chipset supports unaligned access, it might not be
+// enabled in any given system, e.g.:
+// http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/CIHCGCFD.html
+// Therefore, it's generally just not safe to allow unaligned access on any ARM
+// variant.
+//
 // This is a mess, but there's not much we can do about it.
 
 #define UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p))