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Fix endianness detection when __BYTE_ORDER__ is undefined (MSVC) #52

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Fix endianness detection when __BYTE_ORDER__ is undefined (MSVC) #52

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5e4b968
Fix endianness detection when __BYTE_ORDER__ is undefined (MSVC)
MrWater00 Oct 7, 2026
8082e84
Centralize endianness detection and add portable fallback
MrWater00 Oct 8, 2026
63ed897
Use a little-endian and a portable rev8 implementation
MrWater00 Oct 14, 2026
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60 changes: 38 additions & 22 deletions plat_local.h
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Original file line number Diff line number Diff line change
Expand Up @@ -107,31 +107,47 @@ extern "C"

/* revert if not big endian */

#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
/* nop */
#define rev8_be32(x) (x)
#else
/* RISC-V: grev(x, 0x18) or rev8 */
#if defined(SLH_SYS_LITTLE_ENDIAN)

static SLH_INLINE uint32_t rev8_be32(uint32_t x)
{
return ((x & 0xFF000000) >> 24) | ((x & 0x00FF0000) >> 8) |
((x & 0x0000FF00) << 8) | ((x & 0x000000FF) << 24);
}
#endif
/* RISC-V: grev(x, 0x18) or rev8 */
static SLH_INLINE uint32_t rev8_be32(uint32_t x)
{
return ((x & 0xFF000000) >> 24) | ((x & 0x00FF0000) >> 8) |
((x & 0x0000FF00) << 8) | ((x & 0x000000FF) << 24);
}

/* RISC-V: grev(x, 0x38) or rev8(x) */
static SLH_INLINE uint64_t rev8_be64(uint64_t x)
{
return (x << 56) | ((x & 0x000000000000FF00LL) << 40) |
((x & 0x0000000000FF0000LL) << 24) |
((x & 0x00000000FF000000LL) << 8) |
((x & 0x000000FF00000000LL) >> 8) |
((x & 0x0000FF0000000000LL) >> 24) |
((x & 0x00FF000000000000LL) >> 40) | (x >> 56);
}

#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define rev8_be64(x) (x)
#else
/* RISC-V: grev(x, 0x38) or rev8(x) */
static SLH_INLINE uint64_t rev8_be64(uint64_t x)
{
return (x << 56) | ((x & 0x000000000000FF00LL) << 40) |
((x & 0x0000000000FF0000LL) << 24) |
((x & 0x00000000FF000000LL) << 8) | ((x & 0x000000FF00000000LL) >> 8) |
((x & 0x0000FF0000000000LL) >> 24) |
((x & 0x00FF000000000000LL) >> 40) | (x >> 56);
}

/* Portable versions that do not depend on the endianness of the host:
* read the bytes of the argument in memory order and assemble the
* result in big-endian order. */
static SLH_INLINE uint32_t rev8_be32(uint32_t x)
{
const uint8_t *p = (const uint8_t *)&x;
return ((uint32_t)p[0] << 24) | ((uint32_t)p[1] << 16) |
((uint32_t)p[2] << 8) | (uint32_t)p[3];
}

static SLH_INLINE uint64_t rev8_be64(uint64_t x)
{
const uint8_t *p = (const uint8_t *)&x;
return ((uint64_t)p[0] << 56) | ((uint64_t)p[1] << 48) |
((uint64_t)p[2] << 40) | ((uint64_t)p[3] << 32) |
((uint64_t)p[4] << 24) | ((uint64_t)p[5] << 16) |
((uint64_t)p[6] << 8) | (uint64_t)p[7];
}

#endif

/* rotate left */
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22 changes: 22 additions & 0 deletions slh_sys.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,28 @@
#ifndef SLH_SYS_H
#define SLH_SYS_H

/* Try to find endianness, if not forced through CFLAGS already */
#if !defined(SLH_SYS_LITTLE_ENDIAN) && !defined(SLH_SYS_BIG_ENDIAN)
#if defined(__BYTE_ORDER__)
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define SLH_SYS_LITTLE_ENDIAN
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define SLH_SYS_BIG_ENDIAN
#else
#error "__BYTE_ORDER__ defined, but don't recognize value."
#endif
#endif /* __BYTE_ORDER__ */

/* MSVC does not define __BYTE_ORDER__. However, MSVC only supports
* little endian x86, x86_64, and AArch64. It is, hence, safe to assume
* little endian. */
#if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_AMD64) || \
defined(_M_IX86) || defined(_M_ARM64))
#define SLH_SYS_LITTLE_ENDIAN
#endif

#endif /* !SLH_SYS_LITTLE_ENDIAN && !SLH_SYS_BIG_ENDIAN */

/*
* C90 does not have the inline compiler directive yet.
* We don't use it in C90 builds.
Expand Down
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