On 10/13/21 11:41 AM, Philipp Tomsich wrote:
The earlier implementation fell into a corner case for bytes that were 0x01, giving a wrong result (but not affecting our application test cases for strings, as an ASCII value 0x01 is rare in those...).This changes the algorithm to: 1. Mask out the high-bit of each bytes (so that each byte is <= 127). 2. Add 127 to each byte (i.e. if the low 7 bits are not 0, this will overflow into the highest bit of each byte). 3. Bitwise-or the original value back in (to cover those cases where the source byte was exactly 128) to saturate the high-bit. 4. Shift-and-mask (implemented as a mask-and-shift) to extract the MSB of each byte into its LSB. 5. Multiply with 0xff to fan out the LSB to all bits of each byte. Fixes: d7a4fcb034 ("target/riscv: Add orc.b instruction for Zbb, removing gorc/gorci") Signed-off-by: Philipp Tomsich<philipp.toms...@vrull.eu> Reported-by: Vincent Palatin<vpala...@rivosinc.com> ---
Reviewed-by: Richard Henderson <richard.hender...@linaro.org> r~
