diff options
| -rw-r--r-- | src/opts/SkBitmapProcState_opts_SSE2.cpp | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/opts/SkBitmapProcState_opts_SSE2.cpp b/src/opts/SkBitmapProcState_opts_SSE2.cpp index 9ddf269ec9..efe8f4dd2e 100644 --- a/src/opts/SkBitmapProcState_opts_SSE2.cpp +++ b/src/opts/SkBitmapProcState_opts_SSE2.cpp @@ -361,10 +361,31 @@ void ClampX_ClampY_filter_scale_SSE2(const SkBitmapProcState& s, uint32_t xy[], } // while count >= 4 } // if count >= 4 + /* while (count-- > 0) { *xy++ = ClampX_ClampY_pack_filter(fx, maxX, one); fx += dx; } + We'd like to write this as above, but that form allows fx to get 1-iteration too big/small + when count is 0, and this can trigger a UBSAN error, even though we won't in fact use that + last (undefined) value for fx. + + Here is an alternative that should always be efficient, but seems much harder to read: + + if (count > 0) { + for (;;) { + *xy++ = ClampX_ClampY_pack_filter(fx, maxX, one); + if (--count == 0) break; + fx += dx; + } + } + + For now, we'll try this variant: more compact than the if/for version, and we hope the + compiler will get rid of the integer multiply. + */ + for (int i = 0; i < count; ++i) { + *xy++ = ClampX_ClampY_pack_filter(fx + i*dx, maxX, one); + } } } |