From aa043b38a7930725c31a0cd7016986d1c581c573 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Sun, 20 Jan 2019 22:10:36 -0500
Subject: [PATCH] Use OpenMP 2.0 for MSC compilers (GH #787)

---
 cryptest.nmake |  1 +
 salsa.cpp      |  5 +++++
 scrypt.cpp     | 16 ++++++++++++----
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/cryptest.nmake b/cryptest.nmake
index fa71635a..1c547ed3 100644
--- a/cryptest.nmake
+++ b/cryptest.nmake
@@ -155,6 +155,7 @@ LDLIBS =
 # CXXFLAGS = $(CXXFLAGS) /DDEBUG /D_DEBUG /Oi /Oy- /Od /MTd
 # Release build. Add /OPT:REF to linker
 CXXFLAGS = $(CXXFLAGS) /DNDEBUG /D_NDEBUG /Oi /Oy /O2 /MT
+# Linker flags.
 LDFLAGS = $(LDFLAGS) /OPT:REF
 
 # Attempt to detect when <sdkddkver.h> and <winapifamily.h> are available
diff --git a/salsa.cpp b/salsa.cpp
index 148d970a..fb2dc03e 100644
--- a/salsa.cpp
+++ b/salsa.cpp
@@ -90,9 +90,14 @@ void Salsa20_Core(word32* data, unsigned int rounds)
 		x[15] ^= rotlConstant<18>(x[14]+x[13]);
 	}
 
+#ifdef _MSC_VER
+	for (size_t i = 0; i < 16; ++i)
+		data[i] += x[i];
+#else
 	#pragma omp simd
 	for (size_t i = 0; i < 16; ++i)
 		data[i] += x[i];
+#endif
 }
 
 std::string Salsa20_Policy::AlgorithmProvider() const
diff --git a/scrypt.cpp b/scrypt.cpp
index f63a020e..0098d71a 100644
--- a/scrypt.cpp
+++ b/scrypt.cpp
@@ -60,9 +60,14 @@ static inline void BlockCopy(byte* dest, byte* src, size_t len)
 
 static inline void BlockXOR(byte* dest, byte* src, size_t len)
 {
+#ifdef _MSC_VER
+    for (size_t i = 0; i < len; ++i)
+        dest[i] ^= src[i];
+#else
     #pragma omp simd
     for (size_t i = 0; i < len; ++i)
         dest[i] ^= src[i];
+#endif
 }
 
 static inline void PBKDF2_SHA256(byte* buf, size_t dkLen,
@@ -252,10 +257,13 @@ size_t Scrypt::DeriveKey(byte*derived, size_t derivedLen, const byte*secret, siz
     // 1: (B_0 ... B_{p-1}) <-- PBKDF2(P, S, 1, p * MFLen)
     PBKDF2_SHA256(B, B.size(), secret, secretLen, salt, saltLen, 1);
 
+	// Visual Studio and OpenMP 2.0 fixup. We must use int, not size_t.
+	int maxParallel=0;
+	if (!SafeConvert(parallel, maxParallel))
+		maxParallel = std::numeric_limits<int>::max();
+
     #ifdef _OPENMP
-    int threads = STDMIN(omp_get_max_threads(),
-        static_cast<int>(STDMIN(static_cast<size_t>(parallel),
-        static_cast<size_t>(std::numeric_limits<int>::max()))));
+    int threads = STDMIN(omp_get_max_threads(), maxParallel);
     #endif
 
     // http://stackoverflow.com/q/49604260/608639
@@ -267,7 +275,7 @@ size_t Scrypt::DeriveKey(byte*derived, size_t derivedLen, const byte*secret, siz
 
         // 2: for i = 0 to p - 1 do
         #pragma omp for
-        for (size_t i = 0; i < static_cast<size_t>(parallel); ++i)
+        for (int i = 0; i < maxParallel; ++i)
         {
             // 3: B_i <-- MF(B_i, N)
             const ptrdiff_t offset = static_cast<ptrdiff_t>(blockSize*i*128);