diff --git a/libc/intrin/bsf.h b/libc/intrin/bsf.h
index 1a24bf821..090270d11 100644
--- a/libc/intrin/bsf.h
+++ b/libc/intrin/bsf.h
@@ -6,7 +6,6 @@ COSMOPOLITAN_C_START_
 int _bsf(int) pureconst;
 int _bsfl(long) pureconst;
 int _bsfll(long long) pureconst;
-int _bsf128(uintmax_t) pureconst;
 
 #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
 #define _bsf(x)   __builtin_ctz(x)
diff --git a/libc/intrin/bsr.c b/libc/intrin/bsr.c
index b8d8646dc..81a30e1ff 100644
--- a/libc/intrin/bsr.c
+++ b/libc/intrin/bsr.c
@@ -17,40 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/intrin/bsr.h"
-
-static const char kDebruijn[64] = {
-    0,  47, 1,  56, 48, 27, 2,  60, 57, 49, 41, 37, 28, 16, 3,  61,
-    54, 58, 35, 52, 50, 42, 21, 44, 38, 32, 29, 23, 17, 11, 4,  62,
-    46, 55, 26, 59, 40, 36, 15, 53, 34, 51, 20, 43, 31, 22, 10, 45,
-    25, 39, 14, 33, 19, 30, 9,  24, 13, 18, 8,  12, 7,  6,  5,  63,
-};
-
-/**
- * Returns binary logarithm of 𝑥.
- *
- *                           ctz(𝑥)         31^clz(𝑥)   clz(𝑥)
- *       uint32 𝑥  _bsf(𝑥) tzcnt(𝑥)   ffs(𝑥)  _bsr(𝑥) lzcnt(𝑥)
- *     0x00000000      wut       32        0      wut       32
- *     0x00000001        0        0        1        0       31
- *     0x80000001        0        0        1       31        0
- *     0x80000000       31       31       32       31        0
- *     0x00000010        4        4        5        4       27
- *     0x08000010        4        4        5       27        4
- *     0x08000000       27       27       28       27        4
- *     0xffffffff        0        0        1       31        0
- *
- * @param x is a 64-bit integer
- * @return number in range 0..63 or undefined if 𝑥 is 0
- */
-int(_bsrl)(long x) {
-  x |= x >> 1;
-  x |= x >> 2;
-  x |= x >> 4;
-  x |= x >> 8;
-  x |= x >> 16;
-  x |= x >> 32;
-  return kDebruijn[(x * 0x03f79d71b4cb0a89) >> 58];
-}
+// clang-format off
 
 /**
  * Returns binary logarithm of 𝑥.
@@ -70,7 +37,11 @@ int(_bsrl)(long x) {
  * @return number in range 0..31 or undefined if 𝑥 is 0
  */
 int(_bsr)(int x) {
-  return _bsrl((unsigned)x);
+  int r = 0;
+  if(x & 0xFFFF0000u) { x >>= 16; r |= 16; }
+  if(x & 0xFF00) { x >>= 8; r |= 8; }
+  if(x & 0xF0) { x >>= 4; r |= 4; }
+  if(x & 0xC) { x >>= 2; r |= 2; }
+  if(x & 0x2) { r |= 1; }
+  return r;
 }
-
-__weak_reference(_bsrl, _bsrll);
diff --git a/libc/intrin/bsr128.S b/libc/intrin/bsrl.c
similarity index 51%
rename from libc/intrin/bsr128.S
rename to libc/intrin/bsrl.c
index cabcba96e..675f4f54a 100644
--- a/libc/intrin/bsr128.S
+++ b/libc/intrin/bsrl.c
@@ -1,7 +1,7 @@
-/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
-│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
 ╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
 │                                                                              │
 │ Permission to use, copy, modify, and/or distribute this software for         │
 │ any purpose with or without fee is hereby granted, provided that the         │
@@ -16,31 +16,40 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/macros.internal.h"
+#include "libc/intrin/bsr.h"
 
-//	Returns binary logarithm of integer 𝑥.
-//
-//	      uint32 𝑥  _bsf(𝑥) tzcnt(𝑥)   ffs(𝑥)   bsr(𝑥) lzcnt(𝑥)
-//	    0x00000000      wut       32        0      wut       32
-//	    0x00000001        0        0        1        0       31
-//	    0x80000001        0        0        1       31        0
-//	    0x80000000       31       31       32       31        0
-//	    0x00000010        4        4        5        4       27
-//	    0x08000010        4        4        5       27        4
-//	    0x08000000       27       27       28       27        4
-//	    0xffffffff        0        0        1       31        0
-//
-//	@param	rsi:rdi is 128-bit unsigned 𝑥 value
-//	@return	eax number in range [0,128) or undef if 𝑥 is 0
-//	@see	also treasure trove of nearly identical functions
-	.ftrace1
-_bsr128:
-	.ftrace2
-	.leafprologue
-	bsr	%rsi,%rax
-	jnz	2f
-	bsr	%rdi,%rax
-1:	.leafepilogue
-2:	add	$64,%eax
-	jmp	1b
-	.endfn	_bsr128,globl
+static const char kDebruijn[64] = {
+    0,  47, 1,  56, 48, 27, 2,  60, 57, 49, 41, 37, 28, 16, 3,  61,
+    54, 58, 35, 52, 50, 42, 21, 44, 38, 32, 29, 23, 17, 11, 4,  62,
+    46, 55, 26, 59, 40, 36, 15, 53, 34, 51, 20, 43, 31, 22, 10, 45,
+    25, 39, 14, 33, 19, 30, 9,  24, 13, 18, 8,  12, 7,  6,  5,  63,
+};
+
+/**
+ * Returns binary logarithm of 𝑥.
+ *
+ *                           ctz(𝑥)         31^clz(𝑥)   clz(𝑥)
+ *       uint32 𝑥  _bsf(𝑥) tzcnt(𝑥)   ffs(𝑥)  _bsr(𝑥) lzcnt(𝑥)
+ *     0x00000000      wut       32        0      wut       32
+ *     0x00000001        0        0        1        0       31
+ *     0x80000001        0        0        1       31        0
+ *     0x80000000       31       31       32       31        0
+ *     0x00000010        4        4        5        4       27
+ *     0x08000010        4        4        5       27        4
+ *     0x08000000       27       27       28       27        4
+ *     0xffffffff        0        0        1       31        0
+ *
+ * @param x is a 64-bit integer
+ * @return number in range 0..63 or undefined if 𝑥 is 0
+ */
+int(_bsrl)(long x) {
+  x |= x >> 1;
+  x |= x >> 2;
+  x |= x >> 4;
+  x |= x >> 8;
+  x |= x >> 16;
+  x |= x >> 32;
+  return kDebruijn[(x * 0x03f79d71b4cb0a89) >> 58];
+}
+
+__weak_reference(_bsrl, _bsrll);