Incorrect lift of Auto-AND predicates

[toshipiazza]

The publicly available "Hexagon V5x Programmer’s Reference Manual" describes behavior for "auto-AND" predicates in section 6.2.3

If multiple compare instructions in a packet write to the same predicate register, the result is the logical AND of the individual compare results.

binja-hexagon does not seem to support this right now.

test_auto_and_predicates:
  { P0 = cmp.eq(r0,#1)
    P0 = cmp.eq(r0,#2)
    if (P0.new) jump:T 1f }
  { r0 = #0
    jumpr r31 }
1:
  { r0 = #1
    jumpr r31 }

Lifts to

...
   1 @ 00020330  temp90.b = P0
   2 @ 00020330  temp90.b = R0 == 1  # P0's temp written first
   3 @ 00020330  temp90.b = R0 == 2  # P0's temp overwritten instead of AND'd
   4 @ 00020330  if (temp90.b) then 5 else 7
...

[cfircohen]

Nice, I didn't notice that when I read the reference manual. Hexagon keeps surprising me :)

Did you ever see that in compiler generated code? I'd like to prioritize LLIL support for compiler generated code, as getting this plugin to be full spec compatible is very challenging.

[toshipiazza]

I also have not seen this particular construct, but I'll keep my eyes peeled :)