Add portable version and m88k-specific version lb() function, because

unfortunately gcc3 does not have __builtin_clz().

ok miod@ otto@

diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index c4196c7..04f211c 100644 (file)
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: malloc.c,v 1.285 2023/06/04 06:58:33 otto Exp $       */
+/*     $OpenBSD: malloc.c,v 1.286 2023/06/07 12:56:22 aoyama Exp $     */
 /*
  * Copyright (c) 2008, 2010, 2011, 2016, 2023 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -988,12 +988,32 @@ err:
        return NULL;
 }
 
+#if defined(__GNUC__) && __GNUC__ < 4
+static inline unsigned int
+lb(u_int x)
+{
+#if defined(__m88k__)
+       __asm__ __volatile__ ("ff1 %0, %0" : "=r" (x) : "0" (x));
+       return x;
+#else
+       /* portable version */
+       unsigned int count = 0;
+       while ((x & (1U << (sizeof(int) * CHAR_BIT - 1))) == 0) {
+               count++;
+               x <<= 1;
+       }
+       return (sizeof(int) * CHAR_BIT - 1) - count;
+#endif
+}
+#else
+/* using built-in function version */
 static inline unsigned int
 lb(u_int x)
 {
        /* I need an extension just for integer-length (: */
        return (sizeof(int) * CHAR_BIT - 1) - __builtin_clz(x);
 }
+#endif
 
 /* https://pvk.ca/Blog/2015/06/27/linear-log-bucketing-fast-versatile-simple/
    via Tony Finch */