bpf: Improve handling of pattern '<const> <cond_op> <non_const>' in verifier

bpf: Improve handling of pattern '<const> <cond_op> <non_const>' in verifier

Currently, the verifier does not handle '<const> <cond_op> <non_const>' well.
For example,
  ...
  10: (79) r1 = *(u64 *)(r10 -16)       ; R1_w=scalar() R10=fp0
  11: (b7) r2 = 0                       ; R2_w=0
  12: (2d) if r2 > r1 goto pc+2
  13: (b7) r0 = 0
  14: (95) exit
  15: (65) if r1 s> 0x1 goto pc+3
  16: (0f) r0 += r1
  ...
At insn 12, verifier decides both true and false branch are possible, but
actually only false branch is possible.

Currently, the verifier already supports patterns '<non_const> <cond_op> <const>.
Add support for patterns '<const> <cond_op> <non_const>' in a similar way.

Also fix selftest 'verifier_bounds_mix_sign_unsign/bounds checks mixing signed and unsigned, variant 10'
due to this change.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230406164505.1046801-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>