Analytic AntiAlias for Convex Shapes

include/private/SkFixed.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkFixed_DEFINED
 #define SkFixed_DEFINED
 
@@ skipping 70 matching lines @@
     SkToS32(SkTPin<int64_t>((SkLeftShift((int64_t)(numer), 16) / (denom)), SK_MinS32, SK_MaxS32))
 
 //////////////////////////////////////////////////////////////////////////////////////////////////////
 // Now look for ASM overrides for our portable versions (should consider putting this in its own file)
 
 inline SkFixed SkFixedMul_longlong(SkFixed a, SkFixed b) {
     return (SkFixed)((int64_t)a * b >> 16);
 }
 #define SkFixedMul(a,b)     SkFixedMul_longlong(a,b)
 
+inline SkFixed SkFixedMul_lowprec(SkFixed a, SkFixed b) {

[reed1, 2016/08/18 20:31:00]

is this referenced from several files? wondering if we need to add it to this
shared header.

Also, can we add asserts that it never overflows?

e.g.
    if debug mode, compute the answer as int64_t and assert that that fits in
32bits

[liyuqian, 2016/08/22 15:30:48]

It's used in SkEdge.h, SkEdge.cpp (SkAnalyticEdge.cpp in the future), and
SkScan_AAAPath.cpp. I can move it SkEdge.h which is private. I'll also add the
overflow check.

+    return (a >> 8) * (b >> 8);
+}
+
 
 #if defined(SK_CPU_ARM32)
     /* This guy does not handle NaN or other obscurities, but is faster than
        than (int)(x*65536).  When built on Android with -Os, needs forcing
        to inline or we lose the speed benefit.
     */
     SK_ALWAYS_INLINE SkFixed SkFloatToFixed_arm(float x)
     {
         int32_t y, z;
         asm("movs    %1, %3, lsl #1         \n"
@@ skipping 49 matching lines @@
 
 #define SkIntToFixed3232(x)       (SkLeftShift((SkFixed3232)(x), 32))
 #define SkFixed3232ToInt(x)       ((int)((x) >> 32))
 #define SkFixedToFixed3232(x)     (SkLeftShift((SkFixed3232)(x), 16))
 #define SkFixed3232ToFixed(x)     ((SkFixed)((x) >> 16))
 #define SkFloatToFixed3232(x)     ((SkFixed3232)((x) * (65536.0f * 65536.0f)))
 
 #define SkScalarToFixed3232(x)    SkFloatToFixed3232(x)
 
 #endif