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f5d7eef11f
Move fields around to have fewer accesses outside the 128-element Thumb direct access window. In psa_hkdf_key_derivation_t, move the large fields (output_block, prk, hmac) after the state bit-fields. Experimentally, it's slightly better to put hmac last. In aead_operation_t, tag_length was outside the window. The details depend on the sizes of contexts included in ctx. Make the large ctx be the last field. In mbedtls_psa_hmac_operation_t, the opad field is outside the window when SHA-512 is enabled. Moving opad before hash_ctx only saves 4 bytes and made the structure clumsy, so I left it alone. Results (arm-none-eabi-gcc 7.3.1, build_arm_none_eabi_gcc_m0plus build): library/psa_crypto.o: 16246 -> 16166 (diff: 80) library/psa_crypto_aead.o: 952 -> 928 (diff: 24) Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>