From d5d7171f6d21f2894e67bbe47c9a48e01114700f Mon Sep 17 00:00:00 2001
From: Charles Milette <me@charlesmilette.net>
Date: Thu, 25 Jul 2019 16:21:11 -0400
Subject: Fix ARM NEON under MSVC

---
 include/rapidjson/internal/clzll.h | 72 ++++++++++++++++++++++++++++++++++++++
 include/rapidjson/internal/diyfp.h | 18 ++--------
 2 files changed, 74 insertions(+), 16 deletions(-)
 create mode 100644 include/rapidjson/internal/clzll.h

(limited to 'include/rapidjson/internal')

diff --git a/include/rapidjson/internal/clzll.h b/include/rapidjson/internal/clzll.h
new file mode 100644
index 00000000..7c2fa48f
--- /dev/null
+++ b/include/rapidjson/internal/clzll.h
@@ -0,0 +1,72 @@
+// Tencent is pleased to support the open source community by making RapidJSON available.
+//
+// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
+//
+// Licensed under the MIT License (the "License"); you may not use this file except
+// in compliance with the License. You may obtain a copy of the License at
+//
+// http://opensource.org/licenses/MIT
+//
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+#ifndef RAPIDJSON_CLZLL_H_
+#define RAPIDJSON_CLZLL_H_
+
+#include "../rapidjson.h"
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#if defined(_WIN64)
+#pragma intrinsic(_BitScanReverse64)
+#else
+#pragma intrinsic(_BitScanReverse)
+#endif
+#endif
+
+RAPIDJSON_NAMESPACE_BEGIN
+namespace internal {
+
+#if defined(__has_builtin) && __has_builtin(__builtin_clzll)
+#define RAPIDJSON_CLZLL __builtin_clzll
+#else
+
+inline uint32_t clzll(uint64_t x) {
+    // Passing 0 to __builtin_clzll is UB in GCC and results in an
+    // infinite loop in the software implementation.
+    RAPIDJSON_ASSERT(x != 0);
+
+#ifdef _MSC_VER
+    unsigned long r = 0;
+#ifdef _WIN64
+    _BitScanReverse64(&r, x);
+#else
+    // Scan the high 32 bits.
+    if (_BitScanReverse(&r, static_cast<uint32_t>(x >> 32)))
+        return 63 - (r + 32);
+
+    // Scan the low 32 bits.
+    _BitScanReverse(&r, static_cast<uint32_t>(x & 0xFFFFFFFF));
+#endif // _WIN64
+
+    return 63 - r;
+#else
+    uint32_t r;
+    while (!(x & (static_cast<uint64_t>(1) << 63))) {
+        x <<= 1;
+        ++r;
+    }
+
+    return r;
+#endif // _MSC_VER
+}
+
+#define RAPIDJSON_CLZLL RAPIDJSON_NAMESPACE::internal::clzll
+#endif // defined(__has_builtin) && __has_builtin(__builtin_clzll)
+
+} // namespace internal
+RAPIDJSON_NAMESPACE_END
+
+#endif // RAPIDJSON_CLZLL_H_
\ No newline at end of file
diff --git a/include/rapidjson/internal/diyfp.h b/include/rapidjson/internal/diyfp.h
index b6c2cf56..ab5ee071 100644
--- a/include/rapidjson/internal/diyfp.h
+++ b/include/rapidjson/internal/diyfp.h
@@ -20,11 +20,11 @@
 #define RAPIDJSON_DIYFP_H_
 
 #include "../rapidjson.h"
+#include "clzll.h"
 #include <limits>
 
 #if defined(_MSC_VER) && defined(_M_AMD64) && !defined(__INTEL_COMPILER)
 #include <intrin.h>
-#pragma intrinsic(_BitScanReverse64)
 #pragma intrinsic(_umul128)
 #endif
 
@@ -100,22 +100,8 @@ struct DiyFp {
     }
 
     DiyFp Normalize() const {
-        RAPIDJSON_ASSERT(f != 0); // https://stackoverflow.com/a/26809183/291737
-#if defined(_MSC_VER) && defined(_M_AMD64)
-        unsigned long index;
-        _BitScanReverse64(&index, f);
-        return DiyFp(f << (63 - index), e - (63 - index));
-#elif defined(__GNUC__) && __GNUC__ >= 4
-        int s = __builtin_clzll(f);
+        uint32_t s = RAPIDJSON_CLZLL(f);
         return DiyFp(f << s, e - s);
-#else
-        DiyFp res = *this;
-        while (!(res.f & (static_cast<uint64_t>(1) << 63))) {
-            res.f <<= 1;
-            res.e--;
-        }
-        return res;
-#endif
     }
 
     DiyFp NormalizeBoundary() const {
-- 
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