diff --git a/blake3.go b/blake3.go
index 3a5e34d..094582d 100644
--- a/blake3.go
+++ b/blake3.go
@@ -9,6 +9,7 @@ import (
 	"errors"
 	"hash"
 	"io"
+	"math/bits"
 )
 
 const (
@@ -32,31 +33,40 @@ var iv = [8]uint32{
 	0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19,
 }
 
-func g(state *[16]uint32, a, b, c, d int, mx, my uint32) {
-	rotr := func(x uint32, n int) uint32 {
-		return (x >> n) | (x << (32 - n))
-	}
-	state[a] = state[a] + state[b] + mx
-	state[d] = rotr(state[d]^state[a], 16)
-	state[c] = state[c] + state[d]
-	state[b] = rotr(state[b]^state[c], 12)
-	state[a] = state[a] + state[b] + my
-	state[d] = rotr(state[d]^state[a], 8)
-	state[c] = state[c] + state[d]
-	state[b] = rotr(state[b]^state[c], 7)
+func gx(state *[16]uint32, a, b, c, d int, mx uint32) {
+	state[a] += state[b] + mx
+	state[d] = bits.RotateLeft32(state[d]^state[a], -16)
+	state[c] += state[d]
+	state[b] = bits.RotateLeft32(state[b]^state[c], -12)
+}
+
+func gy(state *[16]uint32, a, b, c, d int, my uint32) {
+	state[a] += state[b] + my
+	state[d] = bits.RotateLeft32(state[d]^state[a], -8)
+	state[c] += state[d]
+	state[b] = bits.RotateLeft32(state[b]^state[c], -7)
 }
 
 func round(state *[16]uint32, m *[16]uint32) {
 	// Mix the columns.
-	g(state, 0, 4, 8, 12, m[0], m[1])
-	g(state, 1, 5, 9, 13, m[2], m[3])
-	g(state, 2, 6, 10, 14, m[4], m[5])
-	g(state, 3, 7, 11, 15, m[6], m[7])
+	gx(state, 0, 4, 8, 12, m[0])
+	gy(state, 0, 4, 8, 12, m[1])
+	gx(state, 1, 5, 9, 13, m[2])
+	gy(state, 1, 5, 9, 13, m[3])
+	gx(state, 2, 6, 10, 14, m[4])
+	gy(state, 2, 6, 10, 14, m[5])
+	gx(state, 3, 7, 11, 15, m[6])
+	gy(state, 3, 7, 11, 15, m[7])
+
 	// Mix the diagonals.
-	g(state, 0, 5, 10, 15, m[8], m[9])
-	g(state, 1, 6, 11, 12, m[10], m[11])
-	g(state, 2, 7, 8, 13, m[12], m[13])
-	g(state, 3, 4, 9, 14, m[14], m[15])
+	gx(state, 0, 5, 10, 15, m[8])
+	gy(state, 0, 5, 10, 15, m[9])
+	gx(state, 1, 6, 11, 12, m[10])
+	gy(state, 1, 6, 11, 12, m[11])
+	gx(state, 2, 7, 8, 13, m[12])
+	gy(state, 2, 7, 8, 13, m[13])
+	gx(state, 3, 4, 9, 14, m[14])
+	gy(state, 3, 4, 9, 14, m[15])
 }
 
 func permute(m *[16]uint32) {