From d0d5d4a5f29c8657b0d57563483205ab651a10b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <chfast@gmail.com>
Date: Tue, 9 Nov 2021 16:40:29 +0100
Subject: [PATCH] Remove builtins.h, move clz() to where it is used

---
 lib/ethash/CMakeLists.txt        |  1 -
 lib/ethash/builtins.h            | 43 --------------------------------
 test/experimental/difficulty.cpp | 19 ++++++++++++--
 3 files changed, 17 insertions(+), 46 deletions(-)
 delete mode 100644 lib/ethash/builtins.h

diff --git a/lib/ethash/CMakeLists.txt b/lib/ethash/CMakeLists.txt
index d1a6d65b..973870e0 100644
--- a/lib/ethash/CMakeLists.txt
+++ b/lib/ethash/CMakeLists.txt
@@ -11,7 +11,6 @@ set_target_properties(ethash PROPERTIES C_EXTENSIONS OFF CXX_EXTENSIONS OFF)
 target_link_libraries(ethash PRIVATE ethash::keccak)
 target_include_directories(ethash PUBLIC $<BUILD_INTERFACE:${include_dir}>$<INSTALL_INTERFACE:include>)
 target_sources(ethash PRIVATE
-    builtins.h
     endianness.hpp
     ${include_dir}/ethash/ethash.h
     ${include_dir}/ethash/ethash.hpp
diff --git a/lib/ethash/builtins.h b/lib/ethash/builtins.h
deleted file mode 100644
index e2571841..00000000
--- a/lib/ethash/builtins.h
+++ /dev/null
@@ -1,43 +0,0 @@
-/* ethash: C/C++ implementation of Ethash, the Ethereum Proof of Work algorithm.
- * Copyright 2018-2020 Pawel Bylica.
- * Licensed under the Apache License, Version 2.0.
- */
-
-/**
- * @file
- * Implementation of GCC/clang builtins for MSVC compiler.
- */
-
-#pragma once
-
-#if defined(_MSC_VER) && !defined(__clang__)
-#include <intrin.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/**
- * Returns the number of leading 0-bits in `x`, starting at the most significant bit position.
- * If `x` is 0, the result is undefined.
- */
-inline int __builtin_clz(unsigned int x)
-{
-    unsigned long most_significant_bit;
-    _BitScanReverse(&most_significant_bit, x);
-    return 31 - (int)most_significant_bit;
-}
-
-/**
- * Returns the number of 1-bits in `x`.
- */
-inline int __builtin_popcount(unsigned int x)
-{
-    return (int)__popcnt(x);
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif
diff --git a/test/experimental/difficulty.cpp b/test/experimental/difficulty.cpp
index f5467184..ab100633 100644
--- a/test/experimental/difficulty.cpp
+++ b/test/experimental/difficulty.cpp
@@ -3,11 +3,26 @@
 // Licensed under the Apache License, Version 2.0.
 
 #include "difficulty.h"
-#include "../../lib/ethash/builtins.h"
 #include "../../lib/ethash/endianness.hpp"
 
+#if defined(_MSC_VER) && !defined(__clang__)
+#include <intrin.h>
+#endif
+
 #pragma clang diagnostic ignored "-Wunknown-sanitizers"
 
+inline int clz(uint32_t x) noexcept
+{
+#if defined(_MSC_VER) && !defined(__clang__)
+    unsigned long most_significant_bit;
+    _BitScanReverse(&most_significant_bit, x);
+    return 31 - (int)most_significant_bit;
+#else
+    return x != 0 ? __builtin_clz(x) : 32;
+#endif
+}
+
+
 extern "C" {
 NO_SANITIZE("unsigned-integer-overflow")
 NO_SANITIZE("unsigned-shift-base")
@@ -40,7 +55,7 @@ ethash_hash256 ethash_difficulty_to_boundary(const ethash_hash256* difficulty) n
 
     // Normalize d.
     uint32_t dn[num_words];
-    const int shift = __builtin_clz(d[n - 1]);
+    const int shift = clz(d[n - 1]);
     for (int i = n - 1; i > 0; i--)
         dn[i] = shift ? (d[i] << shift) | (d[i - 1] >> (32 - shift)) : d[i];
     dn[0] = d[0] << shift;