On Wed, 24 May 2023 10:07:47 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> Andrew Haley has updated the pull request incrementally with one additional >> commit since the last revision: >> >> Whitespace > > src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 7097: > >> 7095: // together partial products without any risk of needing to >> 7096: // propagate a carry out. >> 7097: wide_mul(U_0, U_0HI, S_0, R_0); wide_madd(U_0, U_0HI, S_1, >> RR_1); wide_madd(U_0, U_0HI, S_2, RR_0); > > What is `r` corresponding to here? This asserts that 'the top four bits of > each 32-bit subword of "r" are zero'. If `r` is `R_0...R_2` it would seem > broken since we're packing 26-bit values into `R_0...R_2` above in a way that > would break this invariant? No, it doesn't break the invariants. R is the randomly-chosen 128-bit key. It is generated from an initial 128-bit-log string or random bits, then `r &= 0x0ffffffc0ffffffc0ffffffc0fffffff` This 128-bit-long string is split into 26-bit limbs before the intrinsic is called. The zero bits remain zero. When we repack R into two 64-bit registers those zero bits are still zero. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14085#discussion_r1203850178
