Enable 64-bit bignum limbs and add optimized multiplication for Aarch64 #240
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GCC and Clang do not define __ARMCC_VERSION when building for Aarch64. Yet they should also use 64-bit limbs for Aarch64 builds.
x0-x3 are skipped such that function parameters to not have to be moved. MULADDC_INIT and MULADDC_STOP are mostly empty because it is more efficient to keep everything in registers (and that should easily be possible). I considered a MULADDC_HUIT implementation, but could not think of something that would be more efficient than basically 8 consecutive MULADDC_CORE. You could combine the loads and stores, but it's probably more efficient to interleave them with arithmetic, depending on the specific microarchitecture. NEON allows to do a 64x64->128 bit multiplication (and optional accumulation) in one instruction, but is not great at handling carries.
yanesca
approved these changes
Sep 4, 2019
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Thanks for your contribution, @Ko- ! |
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This was Mbed-TLS/mbedtls#1964. The CLA was approved and @yanesca and @Patater reviewed this.