From 1eec9694480eeeff3f139df5b0d91fed400b1814 Mon Sep 17 00:00:00 2001
From: Philip Rebohle <philip.rebohle@tu-dortmund.de>
Date: Sat, 21 Sep 2024 22:46:35 +0200
Subject: [PATCH] [util] Add 64-bit lzcnt

---
 src/util/util_bit.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/util/util_bit.h b/src/util/util_bit.h
index 1df6c17fe..8f7b17dc6 100644
--- a/src/util/util_bit.h
+++ b/src/util/util_bit.h
@@ -152,6 +152,18 @@ namespace dxvk::bit {
     #endif
   }
 
+  inline uint32_t lzcnt(uint64_t n) {
+    #if defined(DXVK_ARCH_X86_64) && ((defined(_MSC_VER) && !defined(__clang__)) || defined(__LZCNT__))
+    return _lzcnt_u64(n);
+    #elif defined(DXVK_ARCH_X86_64) && (defined(__GNUC__) || defined(__clang__))
+    return n != 0 ? __builtin_clzll(n) : 64;
+    #else
+    uint32_t lo = uint32_t(n);
+    uint32_t hi = uint32_t(n >> 32u);
+    return hi ? lzcnt(hi) : lzcnt(lo) + 32u;
+    #endif
+  }
+
   template<typename T>
   uint32_t pack(T& dst, uint32_t& shift, T src, uint32_t count) {
     constexpr uint32_t Bits = 8 * sizeof(T);