Add {read,write}{16,32,64}{le,be} functions

[ruiu]

Summary

Add convenient functions for endianness-aware reads/writes to llvm::support::endian.

[davide]

Probably doesn't really belong to Endian, but it would be nice to have some write8()/read8(). It can be used, e.g. for R_X86_64_8 handling.

[Bigcheese]

lgtm. We should also make sure to remove the 50 other versions of this we have spread throughout llvm.

[ruiu]

I deliberately excluded write8/read8 because single byte read has no
endianness issue. I understand that that feels good for completeness, but
they are for nonexistent issues. We could just cast to uint8_t and do the
stuff.

[Eugene.Zelenko]

Committed in r231002.

include/llvm/Support/Endian.h

typedef detail::packed_endian_specific_integral
                   <uint64_t, native, unaligned> unaligned_uint64_t;
 
 typedef detail::packed_endian_specific_integral
                    <int16_t, native, unaligned> unaligned_int16_t;
 typedef detail::packed_endian_specific_integral
                    <int32_t, native, unaligned> unaligned_int32_t;
 typedef detail::packed_endian_specific_integral
                    <int64_t, native, unaligned> unaligned_int64_t;
-} // end namespace llvm
+
+namespace endian {
+inline uint16_t read16le(const void *p) { return *(ulittle16_t *)p; }
+inline uint32_t read32le(const void *p) { return *(ulittle32_t *)p; }
+inline uint64_t read64le(const void *p) { return *(ulittle64_t *)p; }
+inline uint16_t read16be(const void *p) { return *(ubig16_t *)p; }
+inline uint32_t read32be(const void *p) { return *(ubig32_t *)p; }
+inline uint64_t read64be(const void *p) { return *(ubig64_t *)p; }
+
+inline void write16le(void *p, uint16_t v) { *(ulittle16_t *)p = v; }
+inline void write32le(void *p, uint32_t v) { *(ulittle32_t *)p = v; }
+inline void write64le(void *p, uint64_t v) { *(ulittle64_t *)p = v; }
+inline void write16be(void *p, uint16_t v) { *(ubig16_t *)p = v; }
+inline void write32be(void *p, uint32_t v) { *(ubig32_t *)p = v; }
+inline void write64be(void *p, uint64_t v) { *(ubig64_t *)p = v; }
+} // end namespace endian
 } // end namespace support
+} // end namespace llvm
 
 #endif