revise row blits to keep intermediate precision so that color is preserved when blended against its…

src/opts/SkBlitRow_opts_mips_dsp.cpp

 /*
  * Copyright 2014 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.
  */
 
 #include "SkBlitRow.h"
 #include "SkBlitMask.h"
 #include "SkColorPriv.h"
@@ skipping 771 matching lines @@
         "preceu.ph.qbr   %[t2],    %[t0]              \n\t"
         "preceu.ph.qbl   %[t3],    %[t0]              \n\t"
         "preceu.ph.qbr   %[t4],    %[t1]              \n\t"
         "preceu.ph.qbl   %[t5],    %[t1]              \n\t"
         "muleu_s.ph.qbr  %[t2],    %[t7],    %[t2]    \n\t"
         "muleu_s.ph.qbr  %[t3],    %[t7],    %[t3]    \n\t"
         "muleu_s.ph.qbr  %[t4],    %[t6],    %[t4]    \n\t"
         "muleu_s.ph.qbr  %[t5],    %[t6],    %[t5]    \n\t"
         "addiu           %[src],   %[src],   4        \n\t"
         "addiu           %[count], %[count], -1       \n\t"
-        "precrq.qb.ph    %[t0],    %[t3],    %[t2]    \n\t"
-        "precrq.qb.ph    %[t2],    %[t5],    %[t4]    \n\t"
-        "addu            %[t1],    %[t0],    %[t2]    \n\t"
+        "addu            %[t0],    %[t3],    %[t5]    \n\t"
+        "addu            %[t2],    %[t2],    %[t4]    \n\t"
+        "precrq.qb.ph    %[t1],    %[t0],    %[t2]    \n\t"
         "sw              %[t1],    0(%[dst])          \n\t"
         "b               1b                           \n\t"
         " addi           %[dst],   %[dst],   4        \n\t"
     "2:                                               \n\t"
         ".set            pop                          \n\t"
         : [src]"+r"(src), [dst]"+r"(dst), [count]"+r"(count),
           [t0]"=&r"(t0), [t1]"=&r"(t1), [t2]"=&r"(t2), [t3]"=&r"(t3),
           [t4]"=&r"(t4), [t5]"=&r"(t5), [t6]"=&r"(t6), [t7]"=&r"(t7)
         : [alpha]"r"(alpha)
         : "memory", "hi", "lo"
@@ skipping 138 matching lines @@
     return platform_565_procs_mips_dsp[flags];
 }
 
 SkBlitRow::ColorProc16 SkBlitRow::PlatformColorFactory565(unsigned flags) {
     return nullptr;
 }
 
 SkBlitRow::Proc32 SkBlitRow::PlatformProcs32(unsigned flags) {
     return platform_32_procs_mips_dsp[flags];
 }