crypto: skcipher - Use restrict rather than hand-rolling accesses

Rather than accessing 'alg' directly to avoid the aliasing issue
which leads to unnecessary reloads, use the __restrict keyword
to explicitly tell the compiler that there is no aliasing.

This generates equivalent if not superior code on x86 with gcc 12.

Note that in skcipher_walk_virt the alg assignment is moved after
might_sleep_if because that function is a compiler barrier and
forces a reload.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 8 insertions, 6 deletions

diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index 4f49621d3eb6..d6ae7a86fed2 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -197,13 +197,15 @@ int lskcipher_register_instance(struct crypto_template *tmpl,
 				struct lskcipher_instance *inst);
 
 int skcipher_walk_done(struct skcipher_walk *walk, int res);
-int skcipher_walk_virt(struct skcipher_walk *walk,
-		       struct skcipher_request *req,
+int skcipher_walk_virt(struct skcipher_walk *__restrict walk,
+		       struct skcipher_request *__restrict req,
 		       bool atomic);
-int skcipher_walk_aead_encrypt(struct skcipher_walk *walk,
-			       struct aead_request *req, bool atomic);
-int skcipher_walk_aead_decrypt(struct skcipher_walk *walk,
-			       struct aead_request *req, bool atomic);
+int skcipher_walk_aead_encrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
+int skcipher_walk_aead_decrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
 
 static inline void skcipher_walk_abort(struct skcipher_walk *walk)
 {