I think you didn't understand Chris' post.
C2 is the HotSpot Server compiler. It definitely does not use LLVM anywhere.
Since there is also a programming language called C2, I took a look at the wrong compiler.
Can you provide a link to the source code?
GCC uses a separate representation (RTL) for their backend that is not in SSA form [2]. LLVM stays in SSA form for some backend phases but lowers the SSA form before register allocation (as also mentioned in [1]).
I took a quick look at the C2 and the Graal compiler. C2 seems to use LLVM's code generator (and thus lowers SSA before register allocation) but Graal seems to support SSA-based register allocation, nice.
[1] https://news.ycombinator.com/item?id=11210948
[2] https://en.wikibooks.org/wiki/GNU_C_Compiler_Internals/GNU_C...