Add pinned versions of *ToFixed.

BUG=skia:4632
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1707023002

Review URL: https://codereview.chromium.org/1707023002

1 files changed, 27 insertions, 9 deletions

diff --git a/include/private/SkFixed.h b/include/private/SkFixed.h
index 56821d4d82..c90d5e9ffd 100644
--- a/include/private/SkFixed.h
+++ b/include/private/SkFixed.h
@@ -9,6 +9,8 @@
 #define SkFixed_DEFINED
 
 #include "SkScalar.h"
+#include "math.h"
+
 #include "SkTypes.h"
 
 /** \file SkFixed.h
@@ -29,15 +31,18 @@ typedef int32_t             SkFixed;
 #define SK_FixedRoot2Over2  (0xB505)
 
 #define SkFixedToFloat(x)   ((x) * 1.52587890625e-5f)
-#if 1
-    #define SkFloatToFixed(x)   ((SkFixed)((x) * SK_Fixed1))
-#else
-    // pins over/under flows to max/min int32 (slower than just a cast)
-    static inline SkFixed SkFloatToFixed(float x) {
-        int64_t n = x * SK_Fixed1;
-        return (SkFixed)n;
-    }
-#endif
+#define SkFloatToFixed(x)   ((SkFixed)((x) * SK_Fixed1))
+
+// Pins over/under flows to SK_FixedMax/SK_FixedMin (slower than just a cast).
+static inline SkFixed SkFloatPinToFixed(float x) {
+    x *= SK_Fixed1;
+    // Casting float to int outside the range of the target type (int32_t) is undefined behavior.
+    if (x >= SK_FixedMax) return SK_FixedMax;
+    if (x <= SK_FixedMin) return SK_FixedMin;
+    const SkFixed result = static_cast<SkFixed>(x);
+    SkASSERT(truncf(x) == static_cast<float>(result));
+    return result;
+}
 
 #ifdef SK_DEBUG
     static inline SkFixed SkFloatToFixed_Check(float x) {
@@ -53,6 +58,17 @@ typedef int32_t             SkFixed;
 #define SkFixedToDouble(x)  ((x) * 1.52587890625e-5)
 #define SkDoubleToFixed(x)  ((SkFixed)((x) * SK_Fixed1))
 
+// Pins over/under flows to SK_FixedMax/SK_FixedMin (slower than just a cast).
+static inline SkFixed SkDoublePinToFixed(double x) {
+    x *= SK_Fixed1;
+    // Casting double to int outside the range of the target type (int32_t) is undefined behavior.
+    if (x >= SK_FixedMax) return SK_FixedMax;
+    if (x <= SK_FixedMin) return SK_FixedMin;
+    const SkFixed result = static_cast<SkFixed>(x);
+    SkASSERT(trunc(x) == static_cast<double>(result));
+    return result;
+}
+
 /** Converts an integer to a SkFixed, asserting that the result does not overflow
     a 32 bit signed integer
 */
@@ -147,11 +163,13 @@ inline SkFixed SkFixedMul_longlong(SkFixed a, SkFixed b) {
 
 #define SkFixedToScalar(x)          SkFixedToFloat(x)
 #define SkScalarToFixed(x)          SkFloatToFixed(x)
+#define SkScalarPinToFixed(x)       SkFloatPinToFixed(x)
 
 #else   // SK_SCALAR_IS_DOUBLE
 
 #define SkFixedToScalar(x)          SkFixedToDouble(x)
 #define SkScalarToFixed(x)          SkDoubleToFixed(x)
+#define SkScalarPinToFixed(x)       SkDoublePinToFixed(x)
 
 #endif