From 005abe2e121551cac42e6e9620f4446c7fd4e430 Mon Sep 17 00:00:00 2001
From: tqfx <tqfx@tqfx.org>
Date: Thu, 21 Mar 2024 23:09:09 +0800
Subject: [PATCH] fix BitScanReverse64 in x86

---
 src/math.c  | 6 +++---
 test/math.h | 2 ++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/math.c b/src/math.c
index 2320237..64aab7c 100644
--- a/src/math.c
+++ b/src/math.c
@@ -136,12 +136,12 @@ static A_INLINE int A_U64_BSR(a_u64 x)
 #define A_U64_BSR(x) BitScanReverse64(x)
 static A_INLINE int A_U64_BSR(a_u64 x)
 {
-    unsigned long i = 0, hi = 0;
-    _BitScanReverse(&i, (a_u32)x);
+    unsigned long i = 0, hi;
     if (_BitScanReverse(&hi, x >> 32))
     {
-        i += hi + 1;
+        return (int)hi + 32;
     }
+    _BitScanReverse(&i, (a_u32)x);
     return (int)i;
 }
 #endif /* A_U64_BSR */
diff --git a/test/math.h b/test/math.h
index a76b838..0ba3d5f 100644
--- a/test/math.h
+++ b/test/math.h
@@ -19,6 +19,8 @@ static void test_u32_sqrt(void)
 static void test_u64_sqrt(void)
 {
     TEST_BUG(a_u64_sqrt(A_U64_C(~0)) == A_U32_C(0xFFFFFFFF));
+    TEST_BUG(a_u64_sqrt(A_U64_C(0x10000)) == A_U32_C(0x100));
+    TEST_BUG(a_u64_sqrt(A_U64_C(0xFFFFFFFF)) == A_U32_C(0xFFFF));
     TEST_BUG(a_u64_sqrt(A_U64_C(0x100000000)) == A_U32_C(0x10000));
     TEST_BUG(a_u64_sqrt(A_U64_C(0xFFFFFFFFFFFFFFFF)) == A_U32_C(0xFFFFFFFF));
 }
-- 
2.11.4.GIT