Register Definitions

Integer Registers

Register	ABI Name	Description	Saver
x0	zero	Hard-wired zero
x1	ra	Return address	Caller
x2	sp	Stack pointer	Callee
x3	gp	Global pointer
x4	tp	Thread pointer
x5	t0	Temporary/alternate link register	Caller
x6	t1	Temporaries	Caller
x7	t2	Temporaries	Caller
x8	s0/fp	Saved register/frame pointer	Callee
x9	s1	Saved register	Callee
x10	a0	Function arguments/return values	Caller
x11	a1	Function arguments/return values	Caller
x12	a2	Function arguments	Caller
x13	a3	Function arguments	Caller
x14	a4	Function arguments	Caller
x15	a5	Function arguments	Caller
x16	a6	Function arguments	Caller
x17	a7	Function arguments	Caller
x18	s2	Saved registers	Callee
x19	s3	Saved registers	Callee
x20	s4	Saved registers	Callee
x21	s5	Saved registers	Callee
x22	s6	Saved registers	Callee
x23	s7	Saved registers	Callee
x24	s8	Saved registers	Callee
x25	s9	Saved registers	Callee
x26	s10	Saved registers	Callee
x27	s11	Saved registers	Callee
x28	t3	Temporaries	Caller
x29	t4	Temporaries	Caller
x30	t5	Temporaries	Caller
x31	t6	Temporaries	Caller

Floating Point Registers

Register	ABI Name	Description	Saver
f0	ft0	FP temporaries	Caller
f1	ft1	FP temporaries	Caller
f2	ft2	FP temporaries	Caller
f3	ft3	FP temporaries	Caller
f4	ft4	FP temporaries	Caller
f5	ft5	FP temporaries	Caller
f6	ft6	FP temporaries	Caller
f7	ft7	FP temporaries	Caller
f8	fs0	FP saved registers	Callee
f9	fs1	FP saved registers	Callee
f10	fa0	FP arguments/return values	Caller
f11	fa1	FP arguments/return values	Caller
f12	fa2	FP arguments	Caller
f13	fa3	FP arguments	Caller
f14	fa4	FP arguments	Caller
f15	fa5	FP arguments	Caller
f16	fa6	FP arguments	Caller
f17	fa7	FP arguments	Caller
f18	fs2	FP saved registers	Callee
f19	fs3	FP saved registers	Callee
f20	fs4	FP saved registers	Callee
f21	fs5	FP saved registers	Callee
f22	fs6	FP saved registers	Callee
f23	fs7	FP saved registers	Callee
f24	fs8	FP saved registers	Callee
f25	fs9	FP saved registers	Callee
f26	fs10	FP saved registers	Callee
f27	fs11	FP saved registers	Callee
f28	ft8	FP temporaries	Caller
f29	ft9	FP temporaries	Caller
f30	ft10	FP temporaries	Caller
f31	ft11	FP temporaries	Caller