Use __emul under msvc x86 for fast 64 = 32 * 32

Update uclouvain#220
mayeut · Jul 27, 2015 · b003553 · b003553
1 parent 45ccf50
commit b003553
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Showing 2 changed files with 14 additions and 2 deletions.
diff --git a/src/lib/openjp2/opj_includes.h b/src/lib/openjp2/opj_includes.h
@@ -162,12 +162,16 @@ static INLINE long opj_lrintf(float f) {
 }
 #endif
 
-
-
 #if defined(_MSC_VER) && (_MSC_VER < 1400)
 	#define vsnprintf _vsnprintf
 #endif
 
+/* MSVC x86 is really bad at doing int64 = int32 * int32 on its own. Use intrinsic. */
+#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__INTEL_COMPILER) && defined(_M_IX86)
+#	include <intrin.h>
+#	pragma intrinsic(__emul)
+#endif
+
 #include "opj_inttypes.h"
 #include "opj_clock.h"
 #include "opj_malloc.h"

diff --git a/src/lib/openjp2/opj_intmath.h b/src/lib/openjp2/opj_intmath.h
@@ -184,15 +184,23 @@ Multiply two fixed-precision rational numbers.
 @return Returns a * b
 */
 static INLINE OPJ_INT32 opj_int_fix_mul(OPJ_INT32 a, OPJ_INT32 b) {
+#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__INTEL_COMPILER) && defined(_M_IX86)
+	OPJ_INT64 temp = __emul(a, b);
+#else
 	OPJ_INT64 temp = (OPJ_INT64) a * (OPJ_INT64) b ;
+#endif
 	temp += 4096;
 	assert((temp >> 13) <= (OPJ_INT64)0x7FFFFFFF);
 	assert((temp >> 13) >= (-(OPJ_INT64)0x7FFFFFFF - (OPJ_INT64)1));
 	return (OPJ_INT32) (temp >> 13);
 }
 
 static INLINE OPJ_INT32 opj_int_fix_mul_t1(OPJ_INT32 a, OPJ_INT32 b) {
+#if defined(_MSC_VER) && (_MSC_VER >= 1400) && !defined(__INTEL_COMPILER) && defined(_M_IX86)
+	OPJ_INT64 temp = __emul(a, b);
+#else
 	OPJ_INT64 temp = (OPJ_INT64) a * (OPJ_INT64) b ;
+#endif
 	temp += 4096;
 	assert((temp >> (13 + 11 - T1_NMSEDEC_FRACBITS)) <= (OPJ_INT64)0x7FFFFFFF);
 	assert((temp >> (13 + 11 - T1_NMSEDEC_FRACBITS)) >= (-(OPJ_INT64)0x7FFFFFFF - (OPJ_INT64)1));