From 045441a30502ead533420f479d14b2afe8cc1f8a Mon Sep 17 00:00:00 2001
From: Wunkolo <Wunkolo@gmail.com>
Date: Sat, 27 Apr 2024 17:49:40 -0700
Subject: [PATCH] [Base] Add Windows-ARM64 `bit_count` implementation

Uses intrinsics from https://learn.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics?view=msvc-170
---
 src/xenia/base/math.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/xenia/base/math.h b/src/xenia/base/math.h
index 889cf03ed..c6132f5b4 100644
--- a/src/xenia/base/math.h
+++ b/src/xenia/base/math.h
@@ -133,10 +133,17 @@ constexpr inline uint32_t bit_count(T v) {
 }
 #else
 #if XE_COMPILER_MSVC || XE_COMPILER_INTEL
+#if XE_ARCH_AMD64
 inline uint32_t bit_count(uint32_t v) { return __popcnt(v); }
 inline uint32_t bit_count(uint64_t v) {
   return static_cast<uint32_t>(__popcnt64(v));
 }
+#elif XE_ARCH_ARM64
+inline uint32_t bit_count(uint32_t v) { return _CountOneBits(v); }
+inline uint32_t bit_count(uint64_t v) {
+  return static_cast<uint32_t>(_CountOneBits64(v));
+}
+#endif
 #elif XE_COMPILER_GCC || XE_COMPILER_CLANG
 static_assert(sizeof(unsigned int) == sizeof(uint32_t));
 static_assert(sizeof(unsigned long long) == sizeof(uint64_t));