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author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2017-02-14 21:51:02 +0000 |
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committer | Herbert Xu <herbert@gondor.apana.org.au> | 2017-03-09 18:34:17 +0800 |
commit | 1e704ccb4b116eb4bac25ad5c4fb656ce28c5be0 (patch) | |
tree | d27234f76d57dfb138907c66200e4d7d52ee473c /crypto/sha3_generic.c | |
parent | e61411a03b44b036c309b833396cf105191baa9b (diff) | |
download | linux-crypto-1e704ccb4b116eb4bac25ad5c4fb656ce28c5be0.tar.gz linux-crypto-1e704ccb4b116eb4bac25ad5c4fb656ce28c5be0.zip |
crypto: algapi - annotate expected branch behavior in crypto_inc()
To prevent unnecessary branching, mark the exit condition of the
primary loop as likely(), given that a carry in a 32-bit counter
occurs very rarely.
On arm64, the resulting code is emitted by GCC as
9a8: cmp w1, #0x3
9ac: add x3, x0, w1, uxtw
9b0: b.ls 9e0 <crypto_inc+0x38>
9b4: ldr w2, [x3,#-4]!
9b8: rev w2, w2
9bc: add w2, w2, #0x1
9c0: rev w4, w2
9c4: str w4, [x3]
9c8: cbz w2, 9d0 <crypto_inc+0x28>
9cc: ret
where the two remaining branch conditions (one for size < 4 and one for
the carry) are statically predicted as non-taken, resulting in optimal
execution in the vast majority of cases.
Also, replace the open coded alignment test with IS_ALIGNED().
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/sha3_generic.c')
0 files changed, 0 insertions, 0 deletions