unaligned memory access support for ARMv7

src/globals.h

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 28 matching lines @@
 #define V8_HOST_ARCH_X64 1
 #define V8_HOST_ARCH_64_BIT 1
 #define V8_HOST_CAN_READ_UNALIGNED 1
 #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(__ARMEL__)
 #define V8_HOST_ARCH_ARM 1
 #define V8_HOST_ARCH_32_BIT 1
+// Some CPU-OS combinations allow unaligned access on ARM. We assume
+// that unaligned accesses are not allowed unless the build system
+// defines the CAN_USE_UNALIGNED_ACCESSES macro to be non-zero.
+#if CAN_USE_UNALIGNED_ACCESSES
+#define V8_HOST_CAN_READ_UNALIGNED 1
+#endif
 #elif defined(_MIPS_ARCH_MIPS32R2)
 #define V8_HOST_ARCH_MIPS 1
 #define V8_HOST_ARCH_32_BIT 1
 #else
 #error Host architecture was not detected as supported by v8
 #endif
 
 // Check for supported combinations of host and target architectures.
 #if defined(V8_TARGET_ARCH_IA32) && !defined(V8_HOST_ARCH_IA32)
 #error Target architecture ia32 is only supported on ia32 host
 #endif
 #if defined(V8_TARGET_ARCH_X64) && !defined(V8_HOST_ARCH_X64)
 #error Target architecture x64 is only supported on x64 host
 #endif
 #if (defined(V8_TARGET_ARCH_ARM) && \
     !(defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_ARM)))
 #error Target architecture arm is only supported on arm and ia32 host
 #endif
 #if (defined(V8_TARGET_ARCH_MIPS) && \
     !(defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_MIPS)))
 #error Target architecture mips is only supported on mips and ia32 host
 #endif
 
 // Define unaligned read for the target architectures supporting it.
 #if defined(V8_TARGET_ARCH_X64) || defined(V8_TARGET_ARCH_IA32)
 #define V8_TARGET_CAN_READ_UNALIGNED 1
 #elif V8_TARGET_ARCH_ARM
+// Some CPU-OS combinations allow unaligned access on ARM. We assume
+// that unaligned accesses are not allowed unless the build system
+// defines the CAN_USE_UNALIGNED_ACCESSES macro to be non-zero.
+#if CAN_USE_UNALIGNED_ACCESSES
+#define V8_TARGET_CAN_READ_UNALIGNED 1
+#endif
 #elif V8_TARGET_ARCH_MIPS
 #else
 #error Target architecture is not supported by v8
 #endif
 
 // Support for alternative bool type. This is only enabled if the code is
 // compiled with USE_MYBOOL defined. This catches some nasty type bugs.
 // For instance, 'bool b = "false";' results in b == true! This is a hidden
 // source of bugs.
 // However, redefining the bool type does have some negative impact on some
@@ skipping 537 matching lines @@
                   CMOV = 15,   // x86
                   RDTSC = 4,   // x86
                   CPUID = 10,  // x86
                   VFP3 = 1,    // ARM
                   ARMv7 = 2,   // ARM
                   SAHF = 0};   // x86
 
 } }  // namespace v8::internal
 
 #endif  // V8_GLOBALS_H_