diff --git a/library/stdarch/src/lib.rs b/library/stdarch/src/lib.rs
index 7d6cc0916af3..a981e4107577 100644
--- a/library/stdarch/src/lib.rs
+++ b/library/stdarch/src/lib.rs
@@ -163,6 +163,32 @@ mod v256;
 mod v512;
 mod v64;
 
+mod v32 {
+    use simd_llvm::*;
+
+    define_ty! { i16x2, i16, i16 }
+    define_impl! { i16x2, i16, 2, i16x2, x0, x1 }
+
+    define_ty! { i8x4, i8, i8, i8, i8 }
+    define_impl! { i8x4, i8, 4, i8x4, x0, x1, x2, x3 }
+
+    define_casts!(
+        (i8x4, i32x4, as_i32x4),
+        (i16x2, i64x2, as_i64x4)
+    );
+}
+
+mod v16 {
+    use simd_llvm::*;
+
+    define_ty! { i8x2, i8, i8 }
+    define_impl! { i8x2, i8, 2, i8x2, x0, x1 }
+
+    define_casts!(
+        (i8x2, i64x2, as_i64x2)
+    );
+}
+
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 #[macro_use]
 mod x86;
diff --git a/library/stdarch/src/x86/sse41.rs b/library/stdarch/src/x86/sse41.rs
index 7703754eb4c5..b12a11f3ad89 100644
--- a/library/stdarch/src/x86/sse41.rs
+++ b/library/stdarch/src/x86/sse41.rs
@@ -4,7 +4,7 @@ use std::mem;
 
 #[cfg(test)]
 use stdsimd_test::assert_instr;
-use simd_llvm::{simd_cast, simd_shuffle2, simd_shuffle4, simd_shuffle8};
+use simd_llvm::{simd_shuffle2, simd_shuffle4, simd_shuffle8};
 
 use v128::*;
 
@@ -273,37 +273,32 @@ pub unsafe fn _mm_cvtepi8_epi16(a: i8x16) -> i16x8 {
 #[target_feature = "+sse4.1"]
 #[cfg_attr(test, assert_instr(pmovsxbd))]
 pub unsafe fn _mm_cvtepi8_epi32(a: i8x16) -> i32x4 {
-    let cast = simd_cast::<_, ::v512::i32x16>(a);
-    simd_shuffle4(cast, cast, [0, 1, 2, 3])
+    simd_shuffle4::<_, ::v32::i8x4>(a, a, [0, 1, 2, 3]).as_i32x4()
 }
 
 /// Sign extend packed 8-bit integers in the low 8 bytes of `a` to packed 64-bit integers
-/*
 #[inline(always)]
 #[target_feature = "+sse4.1"]
 #[cfg_attr(test, assert_instr(pmovsxbq))]
 pub unsafe fn _mm_cvtepi8_epi64(a: i8x16) -> i64x2 {
-    simd_cast::<::v16::i8x2, _>(simd_shuffle2(a, a, [0, 1]))
+    simd_shuffle2::<_, ::v16::i8x2>(a, a, [0, 1]).as_i64x2()
 }
-*/
 
 /// Sign extend packed 16-bit integers in `a` to packed 32-bit integers
 #[inline(always)]
 #[target_feature = "+sse4.1"]
 #[cfg_attr(test, assert_instr(pmovsxwd))]
 pub unsafe fn _mm_cvtepi16_epi32(a: i16x8) -> i32x4 {
-    simd_cast::<::v64::i16x4, _>(simd_shuffle4(a, a, [0, 1, 2, 3]))
+    simd_shuffle4::<_, ::v64::i16x4>(a, a, [0, 1, 2, 3]).as_i32x4()
 }
 
 /// Sign extend packed 16-bit integers in a to packed 64-bit integers
-/*
 #[inline(always)]
 #[target_feature = "+sse4.1"]
 #[cfg_attr(test, assert_instr(pmovsxwq))]
 pub unsafe fn _mm_cvtepi16_epi64(a: i16x8) -> i64x2 {
-    simd_cast::<::v32::i16x2, _>(simd_shuffle2(a, a, [0, 1]))
+    simd_shuffle2::<_, ::v32::i16x2>(a, a, [0, 1]).as_i64x4()
 }
-*/
 
 /// Returns the dot product of two f64x2 vectors.
 ///
@@ -829,7 +824,6 @@ mod tests {
         assert_eq!(r, e);
     }
 
-    /*
     #[simd_test = "sse4.1"]
     unsafe fn _mm_cvtepi8_epi64() {
         let a = i8x16::splat(10);
@@ -841,7 +835,6 @@ mod tests {
         let e = i64x2::splat(-10);
         assert_eq!(r, e);
     }
-    */
 
     #[simd_test = "sse4.1"]
     unsafe fn _mm_cvtepi16_epi32() {
@@ -855,7 +848,6 @@ mod tests {
         assert_eq!(r, e);
     }
 
-/*
     #[simd_test = "sse4.1"]
     unsafe fn _mm_cvtepi16_epi64() {
         let a = i16x8::splat(10);
@@ -867,7 +859,7 @@ mod tests {
         let e = i64x2::splat(-10);
         assert_eq!(r, e);
     }
-*/
+
     #[simd_test = "sse4.1"]
     unsafe fn _mm_dp_pd() {
         let a = f64x2::new(2.0, 3.0);