liblzma: Fix the encoder breakage on big endian ARM64

When the 8-byte method was enabled for ARM64, a check for endianness
wasn't added. This broke the LZMA/LZMA2 encoder. Test suite caught it.

Fixes: cd64dd70d5665b6048829c45772d08606f44672e
Co-authored-by: Marcus Comstedt <marcus@mc.pp.se>

diff --git a/src/liblzma/common/memcmplen.h b/src/liblzma/common/memcmplen.h
index 394a4856dd6a0b2d3d42ba3ca20bc97c15e3f43e..86b5d6f37eb385646613a9fd5dbb88d75ea7197f 100644 (file)
--- a/src/liblzma/common/memcmplen.h
+++ b/src/liblzma/common/memcmplen.h
@@ -65,8 +65,7 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
                        || (defined(_MSC_VER) && (defined(_M_X64) \
                                || defined(_M_ARM64) || defined(_M_ARM64EC))))
        // This is only for x86-64 and ARM64 for now. This might be fine on
-       // other 64-bit processors too. On big endian one should use xor
-       // instead of subtraction and switch to __builtin_clzll().
+       // other 64-bit processors too.
        //
        // Reasons to use subtraction instead of xor:
        //
@@ -82,7 +81,11 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
        // version 2023-05-26. https://www.agner.org/optimize/
 #define LZMA_MEMCMPLEN_EXTRA 8
        while (len < limit) {
+#      ifdef WORDS_BIGENDIAN
+               const uint64_t x = read64ne(buf1 + len) ^ read64ne(buf2 + len);
+#      else
                const uint64_t x = read64ne(buf1 + len) - read64ne(buf2 + len);
+#      endif
                if (x != 0) {
        // MSVC or Intel C compiler on Windows
 #      if defined(_MSC_VER) || defined(__INTEL_COMPILER)
@@ -90,6 +93,8 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
                        _BitScanForward64(&tmp, x);
                        len += (uint32_t)tmp >> 3;
        // GCC, Clang, or Intel C compiler
+#      elif defined(WORDS_BIGENDIAN)
+                       len += (uint32_t)__builtin_clzll(x) >> 3;
 #      else
                        len += (uint32_t)__builtin_ctzll(x) >> 3;
 #      endif