Optimize string parsing

src/lib.rs

@@ -4,7 +4,7 @@
 //! most of the design closely with a few exceptions to make it better
 //! fit into the rust ecosystem.
 //!
-//! Note: by default rustc will compile for compatibility, not 
+//! Note: by default rustc will compile for compatibility, not
 //! performance, to take advantage of the simd part of simd json. You
 //! have to use a native cpu target on a avx2 capable host system. An
 //! example how to do this can be found in the `.cargo` directory on
@@ -210,27 +210,13 @@ impl<'de> Deserializer<'de> {
     // fancy in it like object keys
     #[cfg_attr(not(feature = "no-inline"), inline(always))]
     fn parse_short_str_(&mut self) -> Result<&'de str> {
-        let mut padding = [0u8; 32];
         let idx = self.iidx + 1;
         let src: &[u8] = unsafe { &self.input.get_unchecked(idx..) };
 
         //short strings are very common for IDs
-        let v: __m256i = if src.len() >= 32 {
-            // This is safe since we ensure src is at least 32 wide
-            #[allow(clippy::cast_ptr_alignment)]
-            unsafe {
-                _mm256_loadu_si256(src.get_unchecked(..32).as_ptr() as *const __m256i)
-            }
-        } else {
-            unsafe {
-                padding
-                    .get_unchecked_mut(..src.len())
-                    .clone_from_slice(&src);
-                // This is safe since we ensure src is at least 32 wide
-                #[allow(clippy::cast_ptr_alignment)]
-                _mm256_loadu_si256(padding.get_unchecked(..32).as_ptr() as *const __m256i)
-            }
-        };
+        #[allow(clippy::cast_ptr_alignment)]
+        let v: __m256i =
+            unsafe { _mm256_loadu_si256(src.get_unchecked(..32).as_ptr() as *const __m256i) };
         let bs_bits: u32 = unsafe {
             static_cast_u32!(_mm256_movemask_epi8(_mm256_cmpeq_epi8(
                 v,
@@ -241,25 +227,22 @@ impl<'de> Deserializer<'de> {
         let quote_bits = unsafe { static_cast_u32!(_mm256_movemask_epi8(quote_mask)) };
         if (bs_bits.wrapping_sub(1) & quote_bits) != 0 {
             let quote_dist: u32 = trailingzeroes(u64::from(quote_bits)) as u32;
-            let v = unsafe {
-                self.input.get_unchecked(idx..idx + quote_dist as usize) as *const [u8]
-                    as *const str
-            };
             self.str_offset = idx + quote_dist as usize;
-
             unsafe {
-                return Ok(&*v);
+                let v = self.input.get_unchecked(idx..idx + quote_dist as usize) as *const [u8]
+                    as *const str;
+                Ok(&*v)
             }
+        } else {
+            self.parse_str_()
         }
-        self.parse_str_()
     }
 
     #[cfg_attr(not(feature = "no-inline"), inline(always))]
     fn parse_str_(&mut self) -> Result<&'de str> {
         use std::slice::from_raw_parts_mut;
         // Add 1 to skip the initial "
         let idx = self.iidx + 1;
-        let mut padding = [0u8; 32];
         //let mut read: usize = 0;
 
         let needs_relocation = idx - self.str_offset <= 32;
@@ -284,22 +267,9 @@ impl<'de> Deserializer<'de> {
         let mut src_i: usize = 0;
         let mut dst_i: usize = 0;
         loop {
-            let v: __m256i = if src.len() >= src_i + 32 {
-                // This is safe since we ensure src is at least 32 wide
-                #[allow(clippy::cast_ptr_alignment)]
-                unsafe {
-                    _mm256_loadu_si256(src.as_ptr().add(src_i) as *const __m256i)
-                }
-            } else {
-                unsafe {
-                    padding
-                        .get_unchecked_mut(..src.len() - src_i)
-                        .clone_from_slice(src.get_unchecked(src_i..));
-                    // This is safe since we ensure src is at least 32 wide
-                    #[allow(clippy::cast_ptr_alignment)]
-                    _mm256_loadu_si256(padding.as_ptr() as *const __m256i)
-                }
-            };
+            #[allow(clippy::cast_ptr_alignment)]
+            let v: __m256i =
+                unsafe { _mm256_loadu_si256(src.as_ptr().add(src_i) as *const __m256i) };
 
             #[allow(clippy::cast_ptr_alignment)]
             unsafe {