instructions for JIT tail support on ARM
This adds a bunch of instructions we'll need to handle the N < 4 tail
within the JIT code on ARM.
- ldrb/strb are 1-byte load and stores
- sub subtracts without setting flags
- cmp just sets flags (actually just subs with an xzr destination)
- add b and b.lt, just like b.ne
- cbz and cbnz... we only need cbz but I accidentally did cbnz first
Once I add support for forward jumps, we'll be able to use these
instructions to restructure the loop to
entry:
hoisted setup
loop:
if N < 4, jump tail (cmp N,#4; b.lt tail)
... handle 4 values ...
jump loop (b loop)
tail:
if N == 0, jump end (cbz N, end)
... handle 1 value ...
jump tail (b tail)
end:
ret
Change-Id: I62d2d190f670f758197a25d99dfde13362189993
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226828
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed
