1 files changed, 28 insertions, 0 deletions
diff --git a/tests/SkRasterPipelineTest.cpp b/tests/SkRasterPipelineTest.cpp
index bab3d5b63b..33e8b4fe15 100644
--- a/tests/SkRasterPipelineTest.cpp
+++ b/tests/SkRasterPipelineTest.cpp
@@ -262,3 +262,31 @@ DEF_TEST(SkRasterPipeline_2d, r) {
     REPORTER_ASSERT(r, ((rgba[2] >> 8) & 0xff) == 128);
     REPORTER_ASSERT(r, ((rgba[3] >> 8) & 0xff) == 128);
 }
+
+DEF_TEST(SkRasterPipeline_repeat_tiling, r) {
+    // Repeat tiling works roughly like
+    //    v' = v - floor(v / limit) * limit
+    //
+    // If v = 19133558.0f and limit = 9.0f, that's
+    //
+    //    v' = 19133558.0f - floor(19133558.0f / 9.0f) * 9.0f
+    //
+    // The problem comes with that division term.  In infinite precision,
+    // that'd be 2125950 + 8/9, but the nearest float is 2125951.0f.
+    //
+    // Then 2125951.0f * 9.0f = 19133559.0f, which is greater than v,
+    // so v' becomes negative. :'(
+
+    // Here's a regression test to make sure this doesn't happen.
+    float in [4] = {19133558.0f,0,0,0};
+    float out[4 * SkJumper_kMaxStride];
+    SkJumper_TileCtx tile = { 9.0f, 1/9.0f };
+
+    SkRasterPipeline_<256> p;
+    p.append(SkRasterPipeline::uniform_color, in);
+    p.append(SkRasterPipeline::repeat_x, &tile);
+    p.append(SkRasterPipeline::store_rgba, out);
+    p.run(0,0,1,1);
+
+    REPORTER_ASSERT(r, 0.0f <= out[0] && out[0] < 9.0f);
+}