From 65ecf1e43e8d2718a5bb9bb46ae93c581f586341 Mon Sep 17 00:00:00 2001
From: Shawn Hoffman <godisgovernment@gmail.com>
Date: Sat, 9 Jan 2021 23:44:00 -0800
Subject: [PATCH] BitUtils: loosen clz to inline on msvc/arm64

---
 Source/Core/Common/BitUtils.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/Source/Core/Common/BitUtils.h b/Source/Core/Common/BitUtils.h
index bff643855d..1ba34be10f 100644
--- a/Source/Core/Common/BitUtils.h
+++ b/Source/Core/Common/BitUtils.h
@@ -362,7 +362,16 @@ T ExpandValue(T value, size_t left_shift_amount)
          (T(-ExtractBit<0>(value)) >> (BitSize<T>() - left_shift_amount));
 }
 
-constexpr int CountLeadingZeros(uint64_t value)
+// On some compiler / arch combinations, the compiler does not see instrinsics as constexpr, so mark
+// the function as inline instead.
+#if defined(_MSC_VER) && defined(_M_ARM_64)
+#define CONSTEXPR_FROM_INTRINSIC inline
+#else
+#define CONSTEXPR_FROM_INTRINSIC constexpr
+#endif
+
+CONSTEXPR_FROM_INTRINSIC
+int CountLeadingZeros(uint64_t value)
 {
 #if defined(__GNUC__)
   return value ? __builtin_clzll(value) : 64;
@@ -382,7 +391,8 @@ constexpr int CountLeadingZeros(uint64_t value)
 #endif
 }
 
-constexpr int CountLeadingZeros(uint32_t value)
+CONSTEXPR_FROM_INTRINSIC
+int CountLeadingZeros(uint32_t value)
 {
 #if defined(__GNUC__)
   return value ? __builtin_clz(value) : 32;
@@ -402,4 +412,6 @@ constexpr int CountLeadingZeros(uint32_t value)
 #endif
 }
 
+#undef CONSTEXPR_FROM_INTRINSIC
+
 }  // namespace Common