On 03/01/2018 03:59 AM, Peter Maydell wrote: > On 28 February 2018 at 16:48, Richard Henderson > <richard.hender...@linaro.org> wrote: >> Allow the translate subroutines to return false for invalid insns. >> >> At present we can of course invoke an invalid insn exception from within >> the translate subroutine, but in the short term this consolidates code. >> In the long term it would allow the decodetree language to support >> overlapping patterns for ISA extensions. >> >> Signed-off-by: Richard Henderson <richard.hender...@linaro.org> >> --- >> >> Since this makes an ABI change to the translate functions called by the >> decode function, let's make it now before there are any in-tree users. >> >> My SVE branch over-decodes in quite a lot of cases -- e.g. things like >> the 2-bit size field must be 1-3 for fp operands, and so size==0 is >> unallocated. Returning false for these cases allows the actual call >> to unallocated_encoding to be done in one place instead of hundreds. >> >> Longer term, I'm thinking of how to handle decode of overlapping ISA >> extensions. One could allow (specific) overlapping patterns and >> prioritize them in some way (e.g. first in file is first matched). >> My thought is that trans_insn_a would check a cpu feature bit and >> return false if not enabled. Then trans_insn_b would be given its >> chance to handle the insn. > > Reviewed-by: Peter Maydell <peter.mayd...@linaro.org> > > I'll put this into target-arm.next, unless you'd prefer it to go > in via some other route.
That's fine. Thanks! r~
