syntax_data: {"ast_node_type":"other","tokens":[{"end":33,"kind":"keyword","start":0,"text":"xmm0:"}]}
source_snippet:         xmm0: xmm_reg = ["xmm0"],
context_before:         r15b: reg_byte = ["r15b"] % x86_64_only,
context_after:         xmm1: xmm_reg = ["xmm1"],