crypto: arm/chacha20 - always use vrev for 16-bit rotates

The 4-way ChaCha20 NEON code implements 16-bit rotates with vrev32.16, but the one-way code (used on remainder blocks) implements it with vshl + vsri, which is slower. Switch the one-way code to vrev32.16 too. Signed-off-by: Eric Biggers <[email protected]> Acked-by: Ard Biesheuvel <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
qjokers · Aug 3, 2018 · 4e34e51 · 4e34e51
1 parent f53ad3e
commit 4e34e51
Showing 1 changed file with 4 additions and 6 deletions.
diff --git a/arch/arm/crypto/chacha20-neon-core.S b/arch/arm/crypto/chacha20-neon-core.S
@@ -51,9 +51,8 @@ ENTRY(chacha20_block_xor_neon)
 .Ldoubleround:
 	// x0 += x1, x3 = rotl32(x3 ^ x0, 16)
 	vadd.i32	q0, q0, q1
-	veor		q4, q3, q0
-	vshl.u32	q3, q4, #16
-	vsri.u32	q3, q4, #16
+	veor		q3, q3, q0
+	vrev32.16	q3, q3
 
 	// x2 += x3, x1 = rotl32(x1 ^ x2, 12)
 	vadd.i32	q2, q2, q3
@@ -82,9 +81,8 @@ ENTRY(chacha20_block_xor_neon)
 
 	// x0 += x1, x3 = rotl32(x3 ^ x0, 16)
 	vadd.i32	q0, q0, q1
-	veor		q4, q3, q0
-	vshl.u32	q3, q4, #16
-	vsri.u32	q3, q4, #16
+	veor		q3, q3, q0
+	vrev32.16	q3, q3
 
 	// x2 += x3, x1 = rotl32(x1 ^ x2, 12)
 	vadd.i32	q2, q2, q3