crypto: blake2b - Fix clang optimization for ARMv7-M

When building for ARMv7-M, clang-9 or higher tries to unroll some loops,
which ends up confusing the register allocator to the point of generating
rather bad code and using more than the warning limit for stack frames:

warning: stack frame size of 1200 bytes in function 'blake2b_compress' [-Wframe-larger-than=]

Forcing it to not unroll the final loop avoids this problem.

Fixes: 91d689337fe8 ("crypto: blake2b - add blake2b generic implementation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/blake2b_generic.c b/crypto/blake2b_generic.c
index 1d262374fa4e3c4322782c8119b3e32859f521a7..0ffd8d92e308da966c8ab5e0c4473c8d2c0ff87e 100644 (file)
--- a/crypto/blake2b_generic.c
+++ b/crypto/blake2b_generic.c
@@ -129,7 +129,9 @@ static void blake2b_compress(struct blake2b_state *S,
        ROUND(9);
        ROUND(10);
        ROUND(11);
-
+#ifdef CONFIG_CC_IS_CLANG
+#pragma nounroll /* https://bugs.llvm.org/show_bug.cgi?id=45803 */
+#endif
        for (i = 0; i < 8; ++i)
                S->h[i] = S->h[i] ^ v[i] ^ v[i + 8];
 }