Revert "Revert "implement SkScalar versions in terms of float versions""

This reverts commit 0e6db75eebab430e7f6665c8cfa1e7dcd2fef123.

Bug: skia:
Change-Id: I015d01efc58dfe03dae6bcc57c4b1102276e7566
Reviewed-on: https://skia-review.googlesource.com/127967
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

3 files changed, 35 insertions, 27 deletions

diff --git a/include/core/SkScalar.h b/include/core/SkScalar.h
index 9c015e5ea4..938f698e05 100644
--- a/include/core/SkScalar.h
+++ b/include/core/SkScalar.h
@@ -60,7 +60,7 @@ typedef float SkScalar;
 #define SkScalarToFloat(x)      static_cast<float>(x)
 #define SkFloatToScalar(x)      static_cast<SkScalar>(x)
 #define SkScalarToDouble(x)     static_cast<double>(x)
-#define SkDoubleToScalar(x)     static_cast<SkScalar>(x)
+#define SkDoubleToScalar(x)     sk_double_to_float(x)
 
 #define SK_ScalarMin            (-SK_ScalarMax)
 
@@ -68,22 +68,10 @@ static inline bool SkScalarIsNaN(SkScalar x) { return x != x; }
 
 /** Returns true if x is not NaN and not infinite
  */
-static inline bool SkScalarIsFinite(SkScalar x) {
-    // We rely on the following behavior of infinities and nans
-    // 0 * finite --> 0
-    // 0 * infinity --> NaN
-    // 0 * NaN --> NaN
-    SkScalar prod = x * 0;
-    // At this point, prod will either be NaN or 0
-    return !SkScalarIsNaN(prod);
-}
+static inline bool SkScalarIsFinite(SkScalar x) { return sk_float_isfinite(x); }
 
 static inline bool SkScalarsAreFinite(SkScalar a, SkScalar b) {
-    SkScalar prod = 0;
-    prod *= a;
-    prod *= b;
-    // At this point, prod will either be NaN or 0
-    return !SkScalarIsNaN(prod);
+    return sk_float_isfinite(a) && sk_float_isfinite(b);
 }
 
 static inline bool SkScalarsAreFinite(const SkScalar array[], int count) {
@@ -92,7 +80,7 @@ static inline bool SkScalarsAreFinite(const SkScalar array[], int count) {
         prod *= array[i];
     }
     // At this point, prod will either be NaN or 0
-    return !SkScalarIsNaN(prod);
+    return prod == 0;   // if prod is NaN, this check will return false
 }
 
 /**
diff --git a/include/private/SkFloatBits.h b/include/private/SkFloatBits.h
index 2740a25d04..bae1542a31 100644
--- a/include/private/SkFloatBits.h
+++ b/include/private/SkFloatBits.h
@@ -56,6 +56,18 @@ static inline float SkBits2Float(int32_t floatAsBits) {
     return data.fFloat;
 }
 
+constexpr int32_t gFloatBits_exponent_mask = 0x7F800000;
+constexpr int32_t gFloatBits_matissa_mask  = 0x007FFFFF;
+
+static inline bool SkFloatBits_IsFinite(int32_t bits) {
+    return (bits & gFloatBits_exponent_mask) != gFloatBits_exponent_mask;
+}
+
+static inline bool SkFloatBits_IsInf(int32_t bits) {
+    return ((bits & gFloatBits_exponent_mask) == gFloatBits_exponent_mask) &&
+            (bits & gFloatBits_matissa_mask) == 0;
+}
+
 /** Return the float as a 2s compliment int. Just to be used to compare floats
     to each other or against positive float-bit-constants (like 0). This does
     not return the int equivalent of the float, just something cheaper for
diff --git a/include/private/SkFloatingPoint.h b/include/private/SkFloatingPoint.h
index a2e6ee5122..adf7b279b9 100644
--- a/include/private/SkFloatingPoint.h
+++ b/include/private/SkFloatingPoint.h
@@ -12,6 +12,7 @@
 #include "SkTypes.h"
 #include "SkSafe_math.h"
 #include <float.h>
+#include <math.h>
 
 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE1
     #include <xmmintrin.h>
@@ -64,17 +65,17 @@ static inline float sk_float_pow(float base, float exp) {
     #define sk_float_log2(x)        log2f(x)
 #endif
 
-#ifdef SK_BUILD_FOR_WIN
-    #define sk_float_isfinite(x)    _finite(x)
-    #define sk_float_isnan(x)       _isnan(x)
-    static inline int sk_float_isinf(float x) {
-        return x && (x + x == x);
-    }
-#else
-    #define sk_float_isfinite(x)    isfinite(x)
-    #define sk_float_isnan(x)       isnan(x)
-    #define sk_float_isinf(x)       isinf(x)
-#endif
+static inline bool sk_float_isfinite(float x) {
+    return SkFloatBits_IsFinite(SkFloat2Bits(x));
+}
+
+static inline bool sk_float_isinf(float x) {
+    return SkFloatBits_IsInf(SkFloat2Bits(x));
+}
+
+static inline bool sk_float_isnan(float x) {
+    return !(x == x);
+}
 
 #define sk_double_isnan(a)          sk_float_isnan(a)
 
@@ -200,4 +201,11 @@ static inline float sk_ieee_float_divide(float numer, float denom) {
     return numer / denom;
 }
 
+#ifdef __clang__
+__attribute__((no_sanitize("float-divide-by-zero")))
+#endif
+static inline double sk_ieee_double_divide(double numer, double denom) {
+    return numer / denom;
+}
+
 #endif