Revert "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

src/base/build_config.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_BASE_BUILD_CONFIG_H_
 #define V8_BASE_BUILD_CONFIG_H_
 
 #include "include/v8config.h"
 
 // Processor architecture detection.  For more info on what's defined, see:
 //   http://msdn.microsoft.com/en-us/library/b0084kay.aspx
 //   http://www.agner.org/optimize/calling_conventions.pdf
 //   or with gcc, run: "echo | gcc -E -dM -"
 #if defined(_M_X64) || defined(__x86_64__)
 #if defined(__native_client__)
 // For Native Client builds of V8, use V8_TARGET_ARCH_ARM, so that V8
 // generates ARM machine code, together with a portable ARM simulator
 // compiled for the host architecture in question.
 //
 // Since Native Client is ILP-32 on all architectures we use
 // V8_HOST_ARCH_IA32 on both 32- and 64-bit x86.
 #define V8_HOST_ARCH_IA32 1
 #define V8_HOST_ARCH_32_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #else
 #define V8_HOST_ARCH_X64 1
 #if defined(__x86_64__) && __SIZEOF_POINTER__ == 4  // Check for x32.
 #define V8_HOST_ARCH_32_BIT 1
 #else
 #define V8_HOST_ARCH_64_BIT 1
 #endif
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #endif  // __native_client__
 #elif defined(_M_IX86) || defined(__i386__)
 #define V8_HOST_ARCH_IA32 1
 #define V8_HOST_ARCH_32_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #elif defined(__AARCH64EL__)
 #define V8_HOST_ARCH_ARM64 1
 #define V8_HOST_ARCH_64_BIT 1
+#define V8_HOST_CAN_READ_UNALIGNED 1
 #elif defined(__ARMEL__)
 #define V8_HOST_ARCH_ARM 1
 #define V8_HOST_ARCH_32_BIT 1
 #elif defined(__mips64)
 #define V8_HOST_ARCH_MIPS64 1
 #define V8_HOST_ARCH_64_BIT 1
 #elif defined(__MIPSEB__) || defined(__MIPSEL__)
 #define V8_HOST_ARCH_MIPS 1
 #define V8_HOST_ARCH_32_BIT 1
 #else
@@ skipping 104 matching lines @@
 #define V8_TARGET_LITTLE_ENDIAN 1
 #else
 #error Unknown target architecture endianness
 #endif
 
 // Number of bits to represent the page size for paged spaces. The value of 20
 // gives 1Mb bytes per page.
 const int kPageSizeBits = 20;
 
 #endif  // V8_BASE_BUILD_CONFIG_H_