From d8853ec0fd01ecd45c225aee1f22b3d342dcacd7 Mon Sep 17 00:00:00 2001
From: Mike Klein <mtklein@chromium.org>
Date: Sat, 10 Mar 2018 11:34:53 -0500
Subject: exact divide by 255 with NEON

Change-Id: Ib121eb0d5af1f22f48f517fe909112a77d92032e
Reviewed-on: https://skia-review.googlesource.com/113666
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
---
 tests/MathTest.cpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'tests')

diff --git a/tests/MathTest.cpp b/tests/MathTest.cpp
index 94b15207f7..565f76f819 100644
--- a/tests/MathTest.cpp
+++ b/tests/MathTest.cpp
@@ -750,3 +750,23 @@ DEF_TEST(DoubleSaturate32, reporter) {
         REPORTER_ASSERT(reporter, r.fExpectedInt == i);
     }
 }
+
+#if defined(__ARM_NEON)
+    #include <arm_neon.h>
+
+    DEF_TEST(NeonU16Div255, r) {
+
+        for (int v = 0; v <= 255*255; v++) {
+            int want = (v + 127)/255;
+
+            uint16x8_t V = vdupq_n_u16(v);
+            int got = vrshrq_n_u16(vrsraq_n_u16(V, V, 8), 8)[0];
+
+            if (got != want) {
+                SkDebugf("%d -> %d, want %d\n", v, got, want);
+            }
+            REPORTER_ASSERT(r, got == want);
+        }
+    }
+
+#endif
-- 
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