From: Nathan Moinvaziri <nathan@nathanm.com>
Date: Mon, 26 Jan 2026 08:35:21 +0000 (-0800)
Subject: Cleanup and rename bitreverse16 after ctz builtin refactoring
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f83e189ab5857abb1d83412bc1f03081789c1853;p=thirdparty%2Fzlib-ng.git

Cleanup and rename bitreverse16 after ctz builtin refactoring
---

diff --git a/deflate_p.h b/deflate_p.h
index 7b5d56019..f7aea7eec 100644
--- a/deflate_p.h
+++ b/deflate_p.h
@@ -132,7 +132,7 @@ Z_FORCEINLINE static uint16_t bi_reverse(uint16_t code, int len) {
     /* code: the value to invert */
     /* len: its bit length */
     Assert(len >= 1 && len <= 15, "code length must be 1-15");
-    return __builtin_bitreverse16(code) >> (16 - len);
+    return zng_bitreverse16(code) >> (16 - len);
 }
 
 /* ===========================================================================
diff --git a/fallback_builtins.h b/fallback_builtins.h
index 8ccd04e04..e83b9752a 100644
--- a/fallback_builtins.h
+++ b/fallback_builtins.h
@@ -67,11 +67,11 @@ Z_FORCEINLINE static uint32_t zng_ctz64(uint64_t value) {
 #endif
 }
 
-#if !__has_builtin(__builtin_bitreverse16)
-
-#  if defined(ARCH_ARM) && defined(ARCH_64BIT) && !defined(_MSC_VER)
-/* ARM bit reversal for 16-bit values using rbit instruction */
-Z_FORCEINLINE static uint16_t __builtin_bitreverse16(uint16_t value) {
+Z_FORCEINLINE static uint16_t zng_bitreverse16(uint16_t value) {
+#if __has_builtin(__builtin_bitreverse16)
+    return (uint16_t)__builtin_bitreverse16(value);
+#elif defined(ARCH_ARM) && defined(ARCH_64BIT) && !defined(_MSC_VER)
+    /* ARM bit reversal for 16-bit values using rbit instruction */
     uint32_t res;
 #    if __has_builtin(__builtin_rbit)
     res = __builtin_rbit((uint32_t)value);
@@ -79,26 +79,19 @@ Z_FORCEINLINE static uint16_t __builtin_bitreverse16(uint16_t value) {
     __asm__ volatile("rbit %w0, %w1" : "=r"(res) : "r"((uint32_t)value));
 #    endif
     return (uint16_t)(res >> 16);
-}
-#  elif defined(ARCH_LOONGARCH)
-/* LoongArch bit reversal for 16-bit values */
-Z_FORCEINLINE static uint16_t __builtin_bitreverse16(uint16_t value) {
+#elif defined(ARCH_LOONGARCH)
+    /* LoongArch bit reversal for 16-bit values */
     uint32_t res;
     __asm__ volatile("bitrev.w %0, %1" : "=r"(res) : "r"(value));
     return (uint16_t)(res >> 16);
-}
-#  else
-/* Bit reversal for 8-bit values using multiplication method */
-#    define bitrev8(value) \
+#else
+    /* Bit reversal for 8-bit values using multiplication method */
+#  define bitrev8(value) \
     (uint8_t)((((uint8_t)(value) * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32)
-
-/* General purpose bit reversal for 16-bit values */
-Z_FORCEINLINE static uint16_t __builtin_bitreverse16(uint16_t value) {
+    /* General purpose bit reversal for 16-bit values */
     return ((bitrev8(value >> 8) | (uint16_t)bitrev8(value) << 8));
+#  undef bitrev8
+#endif
 }
-#    undef bitrev8
-#  endif
-
-#endif // __builtin_bitreverse16
 
 #endif // include guard FALLBACK_BUILTINS_H
diff --git a/inftrees.c b/inftrees.c
index 5151ff459..00f142157 100644
--- a/inftrees.c
+++ b/inftrees.c
@@ -315,7 +315,7 @@ int Z_INTERNAL zng_inflate_table(codetype type, uint16_t *lens, unsigned codes,
 
         /* backwards increment the len-bit code huff */
         rhuff += (0x8000u >> (len - 1));
-        huff = __builtin_bitreverse16(rhuff);
+        huff = zng_bitreverse16(rhuff);
 
         /* go to next symbol, update count, len */
         sym++;