HelenOS sources
RT_SHIFT 84 kernel/arch/mips32/src/debug/stacktrace.c #define RT_MASK (0x1f << RT_SHIFT)
RT_SHIFT 98 kernel/arch/mips32/src/debug/stacktrace.c ((0x0 << OP_SHIFT) | (SP << RS_SHIFT) | (R0 << RT_SHIFT) | 0x21)
RT_SHIFT 100 kernel/arch/mips32/src/debug/stacktrace.c ((0x0 << OP_SHIFT) | (SP << RD_SHIFT) | (R0 << RT_SHIFT) | 0x21)
RT_SHIFT 102 kernel/arch/mips32/src/debug/stacktrace.c ((0x8 << OP_SHIFT) | (SP << RS_SHIFT) | (SP << RT_SHIFT))
RT_SHIFT 104 kernel/arch/mips32/src/debug/stacktrace.c ((0x9 << OP_SHIFT) | (SP << RS_SHIFT) | (SP << RT_SHIFT))
RT_SHIFT 108 kernel/arch/mips32/src/debug/stacktrace.c ((0x2b << OP_SHIFT) | (RA << RT_SHIFT))
HelenOS homepage, sources at GitHub