The Intra-Procedure-call scratch register.

The Intra-Procedure-call scratch register.

ARM ip レジスタ

r0-r3 are not callee-saved
r4-r11 are callee-saved
r12 (alias ip) is not callee-saved
r13 (alias sp) is callee-saved
r14 (alias lr) is not callee-saved
r15 (alias pc) is the program counter