Question about Souper IR's advantage compare to LLVM IR?

[hstk30-hw]

I see the paper:

why have we developed a new middle-end superoptimizer? First, LLVM IR is the narrow waist in a large
and growing ecosystem of frontends and backends; improvements made at this level can benefit many projects
and billions of end users (via, for example, Android). Second, Souper excels at generating constants, particularly for
Boolean valued variables that are used to control branches.
Constants ripple through the rest of the middle-end and the
full benefits are not realized until constant propagation, dead
code elimination, and other optimization passes have exploited them. Generating constants in the backend would
leave these benefits on the table. Third, the SSA form that
many modern compilers use in their middle ends is effectively a functional programming language [1] that is highly
amenable to automated reasoning techniques.

I still confuse about the advantage compare to LLVM IR.
Is Souper IR can make use of SAT, SMT ... tools?
Or Souper IR eliminates LLVM IR's basic blocks?

[hxm-cpp]

your question is dumb.