From 1c772918c412e395bec10f31518e5011b1338552 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Tue, 18 Oct 2022 18:07:09 +0100
Subject: [PATCH 1/2] Fix MSVC implementation of `CountBits()` function

See: https://learn.microsoft.com/en-us/cpp/intrinsics/bitscanreverse-bitscanreverse64?view=msvc-170
---
 src/int_utils.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/int_utils.h b/src/int_utils.h
index 62b2c38..c6384ca 100644
--- a/src/int_utils.h
+++ b/src/int_utils.h
@@ -149,7 +149,7 @@ static inline int CountBits(I val, int max) {
         ret = _BitScanReverse64(&index, val);
     }
     if (!ret) return 0;
-    return index;
+    return index + 1;
 #else
     while (max && (val >> (max - 1) == 0)) --max;
     return max;

From 0078bedda6078dee91067268ad5fb60b119fd2fb Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Tue, 18 Oct 2022 18:12:08 +0100
Subject: [PATCH 2/2] Ignore `HAVE_CLZ` macro when building with MSVC

`__builtin_clz*` intrinsics are not available for MSVC.
---
 src/int_utils.h | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/int_utils.h b/src/int_utils.h
index c6384ca..d21ba56 100644
--- a/src/int_utils.h
+++ b/src/int_utils.h
@@ -129,17 +129,7 @@ constexpr inline I Mask() { return ((I((I(-1)) << (std::numeric_limits<I>::digit
 /** Compute the smallest power of two that is larger than val. */
 template<typename I>
 static inline int CountBits(I val, int max) {
-#ifdef HAVE_CLZ
-    (void)max;
-    if (val == 0) return 0;
-    if (std::numeric_limits<unsigned>::digits >= std::numeric_limits<I>::digits) {
-        return std::numeric_limits<unsigned>::digits - __builtin_clz(val);
-    } else if (std::numeric_limits<unsigned long>::digits >= std::numeric_limits<I>::digits) {
-        return std::numeric_limits<unsigned long>::digits - __builtin_clzl(val);
-    } else {
-        return std::numeric_limits<unsigned long long>::digits - __builtin_clzll(val);
-    }
-#elif _MSC_VER
+#ifdef _MSC_VER
     (void)max;
     unsigned long index;
     unsigned char ret;
@@ -150,6 +140,16 @@ static inline int CountBits(I val, int max) {
     }
     if (!ret) return 0;
     return index + 1;
+#elif HAVE_CLZ
+    (void)max;
+    if (val == 0) return 0;
+    if (std::numeric_limits<unsigned>::digits >= std::numeric_limits<I>::digits) {
+        return std::numeric_limits<unsigned>::digits - __builtin_clz(val);
+    } else if (std::numeric_limits<unsigned long>::digits >= std::numeric_limits<I>::digits) {
+        return std::numeric_limits<unsigned long>::digits - __builtin_clzl(val);
+    } else {
+        return std::numeric_limits<unsigned long long>::digits - __builtin_clzll(val);
+    }
 #else
     while (max && (val >> (max - 1) == 0)) --max;
     return max;