From b5adffd5c22e9c749b89864a4273bbea99c385ba Mon Sep 17 00:00:00 2001
From: Vadim Pisarevsky <vadim.pisarevsky@gmail.com>
Date: Fri, 24 Jun 2022 14:58:32 +0300
Subject: [PATCH] * cleaned cvRound(), cvFloor() and cvCeil() implementations,
 removed the old non-banking rounding branch completely * enable the use of
 GCC/clang __builtin_*() functions more broadly

---
 .../core/include/opencv2/core/fast_math.hpp   | 66 +++++++------------
 1 file changed, 24 insertions(+), 42 deletions(-)

diff --git a/modules/core/include/opencv2/core/fast_math.hpp b/modules/core/include/opencv2/core/fast_math.hpp
index eb4fbe213b..cd5de0b546 100644
--- a/modules/core/include/opencv2/core/fast_math.hpp
+++ b/modules/core/include/opencv2/core/fast_math.hpp
@@ -128,12 +128,8 @@
     #define CV_INLINE_ISNAN_FLT(value) CV_INLINE_ISNAN_DBL(value)
   #endif
 
-  #if !defined(OPENCV_USE_FASTMATH_BUILTINS) \
-    && ( \
-        defined(__x86_64__) || defined(__i686__) \
-        || defined(__arm__) \
-        || defined(__PPC64__) \
-    )
+  #if !defined(OPENCV_USE_FASTMATH_BUILTINS) && \
+      (defined __GNUC__ || defined __clang__ || defined _MSC_VER)
     /* Let builtin C math functions when available. Dedicated hardware is available to
        round and convert FP values. */
     #define OPENCV_USE_FASTMATH_BUILTINS 1
@@ -201,9 +197,7 @@ cvRound( double value )
 {
 #if defined CV_INLINE_ROUND_DBL
     CV_INLINE_ROUND_DBL(value);
-#elif ((defined _MSC_VER && defined _M_X64) || (defined __GNUC__ && defined __x86_64__ \
-    && defined __SSE2__ && !defined __APPLE__) || CV_SSE2) \
-    && !defined(__CUDACC__)
+#elif (defined _MSC_VER && defined _M_X64) && !defined(__CUDACC__)
     __m128d t = _mm_set_sd( value );
     return _mm_cvtsd_si32(t);
 #elif defined _MSC_VER && defined _M_IX86
@@ -214,12 +208,11 @@ cvRound( double value )
         fistp t;
     }
     return t;
-#elif defined CV_ICC || defined __GNUC__
-    return (int)(lrint(value));
+#elif defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+      defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_lrint(value);
 #else
-    /* it's ok if round does not comply with IEEE754 standard;
-       the tests should allow +/-1 difference when the tested functions use round */
-    return (int)(value + (value >= 0 ? 0.5 : -0.5));
+    return (int)lrint(value);
 #endif
 }
 
@@ -233,11 +226,9 @@ cvRound( double value )
  */
 CV_INLINE int cvFloor( double value )
 {
-#if (defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS) \
-    && ( \
-        defined(__PPC64__) \
-    )
-    return __builtin_floor(value);
+#if defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+    defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_floor(value);
 #else
     int i = (int)value;
     return i - (i > value);
@@ -253,11 +244,9 @@ CV_INLINE int cvFloor( double value )
  */
 CV_INLINE int cvCeil( double value )
 {
-#if (defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS) \
-    && ( \
-        defined(__PPC64__) \
-    )
-    return __builtin_ceil(value);
+#if defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+    defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_ceil(value);
 #else
     int i = (int)value;
     return i + (i < value);
@@ -312,9 +301,7 @@ CV_INLINE int cvRound(float value)
 {
 #if defined CV_INLINE_ROUND_FLT
     CV_INLINE_ROUND_FLT(value);
-#elif ((defined _MSC_VER && defined _M_X64) || (defined __GNUC__ && defined __x86_64__ \
-    && defined __SSE2__ && !defined __APPLE__) || CV_SSE2) \
-    && !defined(__CUDACC__)
+#elif (defined _MSC_VER && defined _M_X64) && !defined(__CUDACC__)
     __m128 t = _mm_set_ss( value );
     return _mm_cvtss_si32(t);
 #elif defined _MSC_VER && defined _M_IX86
@@ -325,12 +312,11 @@ CV_INLINE int cvRound(float value)
         fistp t;
     }
     return t;
-#elif defined CV_ICC || defined __GNUC__
-    return (int)(lrintf(value));
+#elif defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+      defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_lrintf(value);
 #else
-    /* it's ok if round does not comply with IEEE754 standard;
-     the tests should allow +/-1 difference when the tested functions use round */
-    return (int)(value + (value >= 0 ? 0.5f : -0.5f));
+    return (int)lrintf(value);
 #endif
 }
 
@@ -343,11 +329,9 @@ CV_INLINE int cvRound( int value )
 /** @overload */
 CV_INLINE int cvFloor( float value )
 {
-#if (defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS) \
-    && ( \
-        defined(__PPC64__) \
-    )
-    return __builtin_floorf(value);
+#if defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+    defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_floorf(value);
 #else
     int i = (int)value;
     return i - (i > value);
@@ -363,11 +347,9 @@ CV_INLINE int cvFloor( int value )
 /** @overload */
 CV_INLINE int cvCeil( float value )
 {
-#if (defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS) \
-    && ( \
-        defined(__PPC64__) \
-    )
-    return __builtin_ceilf(value);
+#if defined CV__FASTMATH_ENABLE_GCC_MATH_BUILTINS || \
+    defined CV__FASTMATH_ENABLE_CLANG_MATH_BUILTINS
+    return (int)__builtin_ceilf(value);
 #else
     int i = (int)value;
     return i + (i < value);