Fix intrinsics that may be missing on some systems

Create a header to collect all the workarounds for missing intrinsics
in one place

src/strategies/avx2/encode_coding_tree-avx2.c

@@ -26,18 +26,9 @@
 #include "context.h"
 #include "encode_coding_tree-avx2.h"
 #include "encode_coding_tree.h"
+#include "strategies/missing-intel-intrinsics.h"
 #include <immintrin.h>
 
-// GCC headers apparently won't have this at all.. sigh
-#ifndef _andn_u32
-// VS2015 headers apparently won't have this at all.. sigh
-#ifdef __andn_u32
-#define _andn_u32(x, y) (__andn_u32((x), (y)))
-#else
-#define _andn_u32(x, y) ((~(x)) & (y))
-#endif // __andn_u32
-#endif // _andn_u32
-
 /*
  * NOTE: Unlike SSE/AVX comparisons that would return 11 or 00 for gt/lte,
  * this'll use 1x and 0x as bit patterns (x: garbage). A couple extra

src/strategies/missing-intel-intrinsics.h

@@ -0,0 +1,21 @@
+#ifndef MISSING_INTEL_INTRINSICS_H_
+#define MISSING_INTEL_INTRINSICS_H_
+
+#include <immintrin.h>
+
+// Old Visual Studio headers lack the bsrli variant
+#ifndef _mm_bsrli_si128
+  #define _mm_bsrli_si128(a, imm8) _mm_srli_si128((a), (imm8))
+#endif
+
+// GCC headers apparently won't have this at all.. sigh
+#ifndef _andn_u32
+  // VS2015 headers apparently won't have this at all.. sigh
+  #ifdef __andn_u32
+    #define _andn_u32(x, y) (__andn_u32((x), (y)))
+  #else
+    #define _andn_u32(x, y) ((~(x)) & (y))
+  #endif // __andn_u32
+#endif // _andn_u32
+
+#endif

src/strategies/sse41/reg_sad_pow2_widths-sse41.h

@@ -21,8 +21,9 @@
 #ifndef REG_SAD_POW2_WIDTHS_SSE41_H_
 #define REG_SAD_POW2_WIDTHS_SSE41_H_
 
-#include <immintrin.h>
 #include "kvazaar.h"
+#include "strategies/missing-intel-intrinsics.h"
+#include <immintrin.h>
 
 static INLINE uint32_t reg_sad_w0(const kvz_pixel * const data1, const kvz_pixel * const data2,
                            const int32_t height, const uint32_t stride1,