r15d 145 arch/x86/entry/calling.h xorl %r15d, %r15d /* nospec r15 */ r15d 66 arch/x86/include/asm/inst.h .ifc \r32,%r15d r15d 116 tools/perf/arch/x86/util/perf_regs.c SDT_NAME_REG(r15d, r15),