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 |