fix movemask for i16 avx2 (#139)

* fix movemask for i16 avx2

* make test faster

* make movemask test faster on emulators

* skip nightly for MIPS for now

.github/workflows/rust.yml

@@ -75,7 +75,7 @@ jobs:
 
     strategy:
       matrix:
-        rust: [stable,nightly]
+        rust: [stable]
         features: ["", "std"]
 
     steps:

src/i16x16_.rs

@@ -295,7 +295,7 @@ impl i16x16 {
   pub fn move_mask(self) -> i32 {
     pick! {
       if #[cfg(target_feature="avx2")] {
-        (move_mask_i8_m256i(pack_i16_to_i8_m256i(self.avx2,shuffle_ai_i64_all_m256i::<0b00_01_10_11>(self.avx2))) & 0xffff) as i32
+        (move_mask_i8_m256i(pack_i16_to_i8_m256i(self.avx2,shuffle_ai_i64_all_m256i::<0b01_00_11_10>(self.avx2))) & 0xffff) as i32
       } else {
         self.a.move_mask() | (self.b.move_mask() << 8)
       }

tests/all_tests/t_i16x16.rs

@@ -586,8 +586,21 @@ fn impl_from_i8x16() {
 
 #[test]
 fn test_i16x16_move_mask() {
+  let indexes = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];
+
+  for x in 0..256 {
+    // multiply by prime number to mix bits a bit
+    let i = x * 251;
+
+    let a =
+      i16x16::from(indexes.map(|x| if i & (1 << x) != 0 { -1 } else { 0 }));
+
+    assert_eq!(a.move_mask(), i);
+  }
+
   let a =
     i16x16::from([-1, 0, -2, -3, -1, 0, -2, -3, -1, 0, -1, 0, -1, 0, -1, 0]);
+
   let expected = 0b0101010111011101;
   let actual = a.move_mask();
   assert_eq!(expected, actual);