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py: Implement bl/bx instructions for inline Thumb assembler.

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Damien George
2015-02-16 18:17:07 +00:00
parent 42495392da
commit eff10f66a6
7 changed files with 64 additions and 0 deletions
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15
py/asmthumb.c
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@@ -40,6 +40,7 @@
#define SIGNED_FIT8(x) (((x) & 0xffffff80) == 0) || (((x) & 0xffffff80) == 0xffffff80)
#define SIGNED_FIT9(x) (((x) & 0xffffff00) == 0) || (((x) & 0xffffff00) == 0xffffff00)
#define SIGNED_FIT12(x) (((x) & 0xfffff800) == 0) || (((x) & 0xfffff800) == 0xfffff800)
#define SIGNED_FIT23(x) (((x) & 0xffc00000) == 0) || (((x) & 0xffc00000) == 0xffc00000)
struct _asm_thumb_t {
mp_uint_t pass;
@@ -455,6 +456,20 @@ void asm_thumb_bcc_label(asm_thumb_t *as, int cond, uint label) {
}
}
#define OP_BL_HI(byte_offset) (0xf000 | (((byte_offset) >> 12) & 0x07ff))
#define OP_BL_LO(byte_offset) (0xf800 | (((byte_offset) >> 1) & 0x07ff))
void asm_thumb_bl(asm_thumb_t *as, uint label) {
mp_uint_t dest = get_label_dest(as, label);
mp_int_t rel = dest - as->code_offset;
rel -= 4; // account for instruction prefetch, PC is 4 bytes ahead of this instruction
if (SIGNED_FIT23(rel)) {
asm_thumb_op32(as, OP_BL_HI(rel), OP_BL_LO(rel));
} else {
printf("asm_thumb_bl: branch does not fit in 23 bits\n");
}
}
#define OP_BLX(reg) (0x4780 | ((reg) << 3))
#define OP_SVC(arg) (0xdf00 | (arg))