in my disassemble file , i find the operation of k0 in board_init_f but not find in board_init_r, why? is there any other toolchain to compile u-boot for mips?

bfc008e8 <board_init_f>: bfc008e8: 3c1c0001 lui gp,0x1 bfc008ec: 279cdef8 addiu gp,gp,-8456 bfc008f0: 0399e021 addu gp,gp,t9 bfc008f4: 27bdffa8 addiu sp,sp,-88 bfc008f8: afbc0010 sw gp,16(sp) bfc008fc: 8f820124 lw v0,292(gp) bfc00900: afb10044 sw s1,68(sp) bfc00904: afbf0054 sw ra,84(sp) bfc00908: afbc0050 sw gp,80(sp) bfc0090c: afb3004c sw s3,76(sp) bfc00910: afb20048 sw s2,72(sp) bfc00914: afb00040 sw s0,64(sp) bfc00918: 3c114040 lui s1,0x4040 bfc0091c: 02228821 addu s1,s1,v0

bfc00920: 27ba0018 addiu k0,sp,24 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

bfc00bb4 <board_init_r>: bfc00bb4: 3c1c0001 lui gp,0x1 bfc00bb8: 279cdc2c addiu gp,gp,-9172 bfc00bbc: 0399e021 addu gp,gp,t9 bfc00bc0: 27bdffd8 addiu sp,sp,-40 bfc00bc4: afbc0010 sw gp,16(sp) bfc00bc8: afb00018 sw s0,24(sp) bfc00bcc: 00a08021 move s0,a1 bfc00bd0: 00802821 move a1,a0 bfc00bd4: 8f84000c lw a0,12(gp) bfc00bd8: 00000000 nop bfc00bdc: 2484c520 addiu a0,a0,-15072 bfc00be0: afbf0020 sw ra,32(sp) bfc00be4: afbc001c sw gp,28(sp) bfc00be8: 8f9901b0 lw t9,432(gp) bfc00bec: 0320f809 jalr t9 bfc00bf0: 00000000 nop bfc00bf4: 8fbc0010 lw gp,16(sp) bfc00bf8: 8f84000c lw a0,12(gp) bfc00bfc: 00000000 nop bfc00c00: 2484c52c addiu a0,a0,-15060 bfc00c04: 8f990074 lw t9,116(gp) bfc00c08: 0320f809 jalr t9 bfc00c0c: 00000000 nop bfc00c10: 8fbc0010 lw gp,16(sp) bfc00c14: 8f420004 lw v0,4(k0) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ this is gd->flags |= GD_FLG_RELOC; but at this time k0 is still as in board_init_f,

bfc00c18: 3c034040 lui v1,0x4040 bfc00c1c: 00701821 addu v1,v1,s0 bfc00c20: 8f84000c lw a0,12(gp)