Can't describe instructions with overlapping match strings discriminated by "not" constraints #1061
Description
Describe the bug
There is a need to describe sspush and sspopchk, but their respective match strings ostensibly overlap:
sspush : 1100111-----00000100000001110011
sspopchk: 110011011100-----100000001110011
But the not constraint for each distinguishes the two unambiguously, as the first string's variable must be 1 or 5, not 28 (11100) and the second string's variable must be 1 or 5, not 0 (00000).
To Reproduce
With sspush defined with:
encoding:
match: "1100111-----00000100000001110011"
variables:
- name: xs2
location: 24-20
# prettier-ignore
not: [ 0, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 ]
and sspopchk defined with:
encoding:
match: "110011011100-----100000001110011"
variables:
- name: xs1
location: 19-15
# prettier-ignore
not: [ 0, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 ]
Text output/Error Messages
/workspace/riscv-unified-db/backends/cpp_hart_gen/lib/decode_tree.rb:122:in `block in construct_decode_tree': undefined method `match?' for nil:NilClass (NoMethodError)
if inst_format.reverse[cur_range].match?(/^[01]+$/)
^^^^^^^
Additional context
These two instructions are currently represented with incorrect mnemonics as in sspush.x1 and sspush.x5.