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py/asm*: Support assembling code to jump to a register, and get PC+off.

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Useful for position independent code, and implementing state machines.
This commit is contained in:
Damien George
2018-08-16 13:45:24 +10:00
parent f7d6108d1a
commit 2964b41c28
10 changed files with 122 additions and 0 deletions
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9
py/asmthumb.c
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@@ -310,6 +310,15 @@ void asm_thumb_mov_reg_local_addr(asm_thumb_t *as, uint rlo_dest, int local_num)
asm_thumb_op16(as, OP_ADD_REG_SP_OFFSET(rlo_dest, word_offset));
}
void asm_thumb_mov_reg_pcrel(asm_thumb_t *as, uint rlo_dest, uint label) {
mp_uint_t dest = get_label_dest(as, label);
mp_int_t rel = dest - as->base.code_offset;
rel -= 4 + 4; // adjust for mov_reg_i16 and then PC+4 prefetch of add_reg_reg
rel |= 1; // to stay in Thumb state when jumping to this address
asm_thumb_mov_reg_i16(as, ASM_THUMB_OP_MOVW, rlo_dest, rel); // 4 bytes
asm_thumb_add_reg_reg(as, rlo_dest, ASM_THUMB_REG_R15); // 2 bytes
}
// this could be wrong, because it should have a range of +/- 16MiB...
#define OP_BW_HI(byte_offset) (0xf000 | (((byte_offset) >> 12) & 0x07ff))
#define OP_BW_LO(byte_offset) (0xb800 | (((byte_offset) >> 1) & 0x07ff))