Re: Byte Addressability And Beyond

According to Terje Mathisen  <terje.mathisen@tmsw.no>:

It's almost like the perfect application of risc instruction design:
a long sequence of individual instructions of conditional branches,
bit field extracts, inserts, and shifts, is replace in HW by
a small number of muxes that can to the same in one clock.

>
If that CU14 can also return the number of bytes consumed, along with
the resulting 32-bit character, then it would be perfect. Is that what
it is doing?

You give it registers with two addresses and two lengths, and it
converts the source UTF-8 code points to destination UTF-32 until it
runs out of input, fills the output, gets an invalid character, or an
interrupt. It updates the addresses and lengths. Other than optionally
checking for invalid UTF-8 it does not interpret the code points.

The condition code tells you which it was.  If it was an interrupt, you just
branch back and keep going.

There's an extra cost flag whether to test for invalid UTF-8.

Read all about it: https://www.vm.ibm.com/library/other/22783213.pdf

It's on page 7-251.

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