fast sk4f <-> sk4i SSE methods

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1707673002
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1707673002
diff --git a/tests/SkNxTest.cpp b/tests/SkNxTest.cpp
index e329e17..57e659e 100644
--- a/tests/SkNxTest.cpp
+++ b/tests/SkNxTest.cpp
@@ -237,6 +237,22 @@
     REPORTER_ASSERT(r, f4[3] == 20);
 }
 
+DEF_TEST(SkNx_int_float, r) {
+    Sk4f f(-2.3f, 1.0f, 0.45f, 0.6f);
+
+    Sk4i i = SkNx_cast<int>(f);
+    REPORTER_ASSERT(r, i[0] == -2);
+    REPORTER_ASSERT(r, i[1] ==  1);
+    REPORTER_ASSERT(r, i[2] ==  0);
+    REPORTER_ASSERT(r, i[3] ==  0);
+
+    f = SkNx_cast<float>(i);
+    REPORTER_ASSERT(r, f[0] == -2.0f);
+    REPORTER_ASSERT(r, f[1] ==  1.0f);
+    REPORTER_ASSERT(r, f[2] ==  0.0f);
+    REPORTER_ASSERT(r, f[3] ==  0.0f);
+}
+
 #include "SkRandom.h"
 
 DEF_TEST(SkNx_u16_float, r) {