syntax_data: {"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // - LLVM has reserve-{g,o,l,i}N feature to reserve each general-purpose registers.
context_before:         // FIXME:
context_after:         // - g2-g4 are reserved for application (optional in both LLVM and GCC, and GCC has -mno-app-regs option to reserve them).