sha3.c: refactor backends so they only implement permute_n()

i verified that (gcc, at least) does constant propagation and inlines
permute_n_<backend> and that this change does not affect performance.

bench results, before:
  pabs@flex:~/git/sha3/tests/bench> ./bench
  info: cpucycles: version=20240318 implementation=amd64-pmc persecond=4800000000
  info: backend=avx512 num_trials=100000 src_lens=64,256,1024,4096,16384 dst_lens=32
  function,dst_len,64,256,1024,4096,16384
  sha3_224,28,15.4,7.8,7.8,7.1,7.0
  sha3_256,32,15.5,7.8,7.8,7.6,7.4
  sha3_384,48,15.5,11.7,9.8,9.8,9.7
  sha3_512,64,15.6,15.5,14.6,13.9,13.9
  shake128,32,15.5,7.8,6.9,6.2,6.1
  shake256,32,15.5,7.8,7.9,7.6,7.4

bench results, after change:
  pabs@flex:~/git/sha3/tests/bench> ./bench
  info: cpucycles: version=20240318 implementation=amd64-pmc persecond=4800000000
  info: backend=avx512 num_trials=100000 src_lens=64,256,1024,4096,16384 dst_lens=32
  function,dst_len,64,256,1024,4096,16384
  sha3_224,28,15.4,7.8,7.8,7.1,7.0
  sha3_256,32,15.6,7.8,7.8,7.6,7.4
  sha3_384,48,15.6,11.7,9.8,9.8,9.7
  sha3_512,64,15.6,15.5,14.6,13.8,13.8
  shake128,32,15.6,7.9,6.9,6.2,6.1
  shake256,32,15.7,7.9,7.9,7.6,7.4

1 files changed, 21 insertions, 40 deletions

diff --git a/sha3.c b/sha3.c
index 6f936b9..8563d27 100644
--- a/sha3.c
+++ b/sha3.c
@@ -231,23 +231,6 @@ static inline void permute_n_scalar(uint64_t a[static 25], const size_t num_roun
     iota(a, (SHA3_NUM_ROUNDS - num_rounds + i));
   }
 }
-
-/**
- * @brief 24 round scalar Keccak permutation.
- * @param[in,out] a Keccak state (array of 25 64-bit integers).
- */
-static inline void permute_scalar(uint64_t a[static 25]) {
-  permute_n_scalar(a, 24);
-}
-
-/**
- * @brief 12 round scalar Keccak permutation.
- * @note Only used by TurboSHAKE and KangarooTwelve.
- * @param[in,out] a Keccak state (array of 25 64-bit integers).
- */
-static inline void permute12_scalar(uint64_t a[static 25]) {
-  permute_n_scalar(a, 12);
-}
 #endif /* (SHA3_BACKEND == BACKEND_SCALAR) || defined(SHA3_TEST) */
 
 #if SHA3_BACKEND == BACKEND_AVX512
@@ -477,36 +460,34 @@ static inline void permute_n_avx512(uint64_t s[static 25], const size_t num_roun
   _mm512_mask_storeu_epi64(s + 5 * 3, 0x1f, r3);
   _mm512_mask_storeu_epi64(s + 5 * 4, 0x1f, r4);
 }
+#endif /* SHA3_BACKEND == BACKEND_AVX512 */
+
+#if SHA3_BACKEND == BACKEND_AVX512
+// use avx512 backend
+#define permute_n permute_n_avx512
+#elif SHA3_BACKEND == BACKEND_SCALAR
+// use scalar backend
+#define permute_n permute_n_scalar
+#else
+#error "unknown sha3 backend"
+#endif /* SHA3_BACKEND */
 
 /**
- * @brief 24 round AVX-512 Keccak permutation.
+ * @brief 24 round Keccak permutation.
  * @param[in,out] a Keccak state (array of 25 64-bit integers).
  */
-static inline void permute_avx512(uint64_t s[static 25]) {
-  permute_n_avx512(s, 24);
+static inline void permute(uint64_t s[static 25]) {
+  permute_n(s, 24);
 }
 
 /**
- * @brief 12 round AVX-512 Keccak permutation.
+ * @brief 12 round Keccak permutation.
  * @note Only used by TurboSHAKE and KangarooTwelve.
  * @param[in,out] a Keccak state (array of 25 64-bit integers).
  */
-static inline void permute12_avx512(uint64_t s[static 25]) {
-  permute_n_avx512(s, 12);
+static inline void permute12(uint64_t s[static 25]) {
+  permute_n(s, 12);
 }
-#endif /* SHA3_BACKEND == BACKEND_AVX512 */
-
-#if SHA3_BACKEND == BACKEND_AVX512
-// use avx512 backend
-#define permute permute_avx512
-#define permute12 permute12_avx512
-#elif SHA3_BACKEND == BACKEND_SCALAR
-// use scalar backend
-#define permute permute_scalar
-#define permute12 permute12_scalar
-#else
-#error "unknown sha3 backend"
-#endif /* SHA3_BACKEND */
 
 // absorb message into state, return updated byte count
 // used by `hash_absorb()`, `hash_once()`, and `xof_absorb_raw()`
@@ -2231,7 +2212,7 @@ static void test_permute_scalar(void) {
 
     uint64_t got[25] = { 0 };
     memcpy(got, PERMUTE_TESTS[i].a, sizeof(got));
-    permute_scalar(got);
+    permute_n_scalar(got, 24); // call permute_n_scalar() directly
 
     if (memcmp(got, PERMUTE_TESTS[i].exp, exp_len)) {
       fail_test(__func__, "", (uint8_t*) got, exp_len, (uint8_t*) PERMUTE_TESTS[i].exp, exp_len);
@@ -2246,7 +2227,7 @@ static void test_permute_avx512(void) {
 
     uint64_t got[25] = { 0 };
     memcpy(got, PERMUTE_TESTS[i].a, sizeof(got));
-    permute_avx512(got);
+    permute_n_avx512(got, 24); // call permute_n_avx512() directly
 
     if (memcmp(got, PERMUTE_TESTS[i].exp, exp_len)) {
       fail_test(__func__, "", (uint8_t*) got, exp_len, (uint8_t*) PERMUTE_TESTS[i].exp, exp_len);
@@ -2271,7 +2252,7 @@ static void test_permute12_scalar(void) {
 
     uint64_t got[25] = { 0 };
     memcpy(got, PERMUTE12_TESTS[i].a, sizeof(got));
-    permute12_scalar(got);
+    permute_n_scalar(got, 12); // call permute_n_scalar() directly
 
     if (memcmp(got, PERMUTE12_TESTS[i].exp, exp_len)) {
       fail_test(__func__, "", (uint8_t*) got, exp_len, (uint8_t*) PERMUTE12_TESTS[i].exp, exp_len);
@@ -2286,7 +2267,7 @@ static void test_permute12_avx512(void) {
 
     uint64_t got[25] = { 0 };
     memcpy(got, PERMUTE12_TESTS[i].a, sizeof(got));
-    permute12_avx512(got);
+    permute_n_avx512(got, 12); // call permute_n_avx512() directly
 
     if (memcmp(got, PERMUTE12_TESTS[i].exp, exp_len)) {
       fail_test(__func__, "", (uint8_t*) got, exp_len, (uint8_t*) PERMUTE12_TESTS[i].exp, exp_len);