Drop unnecessary SIMD subtraction in ChaCha20 `round`

[rust-lightning] / lightning / src / util / chacha20.rs

diff --git a/lightning/src/util/chacha20.rs b/lightning/src/util/chacha20.rs
index f46b344f2ce144c235e40e041743e707570e43a5..87500d88d5206c67d3a4d93a1d212a5a018e29cb 100644 (file)
--- a/lightning/src/util/chacha20.rs
+++ b/lightning/src/util/chacha20.rs
@@ -43,16 +43,16 @@ mod real_chacha {
                        u32x4(self.0 ^ rhs.0, self.1 ^ rhs.1, self.2 ^ rhs.2, self.3 ^ rhs.3)
                }
        }
-       impl ::core::ops::Shr<u32x4> for u32x4 {
+       impl ::core::ops::Shr<u8> for u32x4 {
                type Output = u32x4;
-               fn shr(self, rhs: u32x4) -> u32x4 {
-                       u32x4(self.0 >> rhs.0, self.1 >> rhs.1, self.2 >> rhs.2, self.3 >> rhs.3)
+               fn shr(self, shr: u8) -> u32x4 {
+                       u32x4(self.0 >> shr, self.1 >> shr, self.2 >> shr, self.3 >> shr)
                }
        }
-       impl ::core::ops::Shl<u32x4> for u32x4 {
+       impl ::core::ops::Shl<u8> for u32x4 {
                type Output = u32x4;
-               fn shl(self, rhs: u32x4) -> u32x4 {
-                       u32x4(self.0 << rhs.0, self.1 << rhs.1, self.2 << rhs.2, self.3 << rhs.3)
+               fn shl(self, shl: u8) -> u32x4 {
+                       u32x4(self.0 << shl, self.1 << shl, self.2 << shl, self.3 << shl)
                }
        }
        impl u32x4 {
@@ -118,31 +118,25 @@ mod real_chacha {
        macro_rules! round{
                ($state: expr) => {{
                        $state.a = $state.a + $state.b;
-                       rotate!($state.d, $state.a, S16);
+                       rotate!($state.d, $state.a, 16);
                        $state.c = $state.c + $state.d;
-                       rotate!($state.b, $state.c, S12);
+                       rotate!($state.b, $state.c, 12);
                        $state.a = $state.a + $state.b;
-                       rotate!($state.d, $state.a, S8);
+                       rotate!($state.d, $state.a, 8);
                        $state.c = $state.c + $state.d;
-                       rotate!($state.b, $state.c, S7);
+                       rotate!($state.b, $state.c, 7);
                }}
        }
 
        macro_rules! rotate {
-               ($a: expr, $b: expr, $c:expr) => {{
+               ($a: expr, $b: expr, $rot: expr) => {{
                        let v = $a ^ $b;
-                       let r = S32 - $c;
+                       let r = 32 - $rot;
                        let right = v >> r;
-                       $a = (v << $c) ^ right
+                       $a = (v << $rot) ^ right
                }}
        }
 
-       const S32:u32x4 = u32x4(32, 32, 32, 32);
-       const S16:u32x4 = u32x4(16, 16, 16, 16);
-       const S12:u32x4 = u32x4(12, 12, 12, 12);
-       const S8:u32x4 = u32x4(8, 8, 8, 8);
-       const S7:u32x4 = u32x4(7, 7, 7, 7);
-
        impl ChaCha20 {
                pub fn new(key: &[u8], nonce: &[u8]) -> ChaCha20 {
                        assert!(key.len() == 16 || key.len() == 32);