MaybeUninit: update to into_initialized (#679)

* MaybeUninit: update to into_initialized

* fix unused import

Author: RalfJung

crates/core_arch/src/x86/avx.rs

@@ -2959,7 +2959,7 @@ pub unsafe fn _mm256_zextpd128_pd256(a: __m128d) -> __m256d {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm256_undefined_ps() -> __m256 {
     // FIXME: this function should return MaybeUninit<__m256>
-    mem::MaybeUninit::<__m256>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m256>::uninitialized().into_initialized()
 }
 
 /// Return vector of type `__m256d` with undefined elements.
@@ -2971,7 +2971,7 @@ pub unsafe fn _mm256_undefined_ps() -> __m256 {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm256_undefined_pd() -> __m256d {
     // FIXME: this function should return MaybeUninit<__m256d>
-    mem::MaybeUninit::<__m256d>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m256d>::uninitialized().into_initialized()
 }
 
 /// Return vector of type __m256i with undefined elements.
@@ -2983,7 +2983,7 @@ pub unsafe fn _mm256_undefined_pd() -> __m256d {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm256_undefined_si256() -> __m256i {
     // FIXME: this function should return MaybeUninit<__m256i>
-    mem::MaybeUninit::<__m256i>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m256i>::uninitialized().into_initialized()
 }
 
 /// Set packed __m256 returned vector with the supplied values.

crates/core_arch/src/x86/avx512f.rs

@@ -1,7 +1,7 @@
 use core_arch::simd::*;
 use core_arch::simd_llvm::*;
 use core_arch::x86::*;
-use mem::{self, MaybeUninit};
+use mem;
 
 #[cfg(test)]
 use stdsimd_test::assert_instr;
@@ -15,7 +15,7 @@ use stdsimd_test::assert_instr;
 pub unsafe fn _mm512_abs_epi32(a: __m512i) -> __m512i {
     let a = a.as_i32x16();
     // all-0 is a properly initialized i32x16
-    let zero: i32x16 = MaybeUninit::zeroed().into_inner();
+    let zero: i32x16 = mem::zeroed();
     let sub = simd_sub(zero, a);
     let cmp: i32x16 = simd_gt(a, zero);
     mem::transmute(simd_select(cmp, a, sub))
@@ -56,7 +56,7 @@ pub unsafe fn _mm512_maskz_abs_epi32(k: __mmask16, a: __m512i) -> __m512i {
 #[cfg_attr(test, assert_instr(vxorps))]
 pub unsafe fn _mm512_setzero_si512() -> __m512i {
     // All-0 is a properly initialized __m512i
-    MaybeUninit::zeroed().into_inner()
+    mem::zeroed()
 }
 
 /// Set packed 32-bit integers in `dst` with the supplied values in reverse

crates/core_arch/src/x86/sse.rs

@@ -1886,7 +1886,7 @@ pub unsafe fn _mm_prefetch(p: *const i8, strategy: i32) {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm_undefined_ps() -> __m128 {
     // FIXME: this function should return MaybeUninit<__m128>
-    mem::MaybeUninit::<__m128>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m128>::uninitialized().into_initialized()
 }
 
 /// Transpose the 4x4 matrix formed by 4 rows of __m128 in place.

crates/core_arch/src/x86/sse2.rs

@@ -2856,7 +2856,7 @@ pub unsafe fn _mm_castsi128_ps(a: __m128i) -> __m128 {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm_undefined_pd() -> __m128d {
     // FIXME: this function should return MaybeUninit<__m128d>
-    mem::MaybeUninit::<__m128d>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m128d>::uninitialized().into_initialized()
 }
 
 /// Return vector of type __m128i with undefined elements.
@@ -2867,7 +2867,7 @@ pub unsafe fn _mm_undefined_pd() -> __m128d {
 #[stable(feature = "simd_x86", since = "1.27.0")]
 pub unsafe fn _mm_undefined_si128() -> __m128i {
     // FIXME: this function should return MaybeUninit<__m128i>
-    mem::MaybeUninit::<__m128i>::uninitialized().into_inner()
+    mem::MaybeUninit::<__m128i>::uninitialized().into_initialized()
 }
 
 /// The resulting `__m128d` element is composed by the low-order values of