diff options
| -rw-r--r-- | py/asmxtensa.c | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/py/asmxtensa.c b/py/asmxtensa.c index 2b36a56ea..fd71dedb1 100644 --- a/py/asmxtensa.c +++ b/py/asmxtensa.c @@ -41,6 +41,7 @@ #endif #define WORD_SIZE (4) +#define SIGNED_FIT6(x) ((((x) & 0xffffffe0) == 0) || (((x) & 0xffffffe0) == 0xffffffe0)) #define SIGNED_FIT8(x) ((((x) & 0xffffff80) == 0) || (((x) & 0xffffff80) == 0xffffff80)) #define SIGNED_FIT12(x) ((((x) & 0xfffff800) == 0) || (((x) & 0xfffff800) == 0xfffff800)) #define SIGNED_FIT18(x) ((((x) & 0xfffe0000) == 0) || (((x) & 0xfffe0000) == 0xfffe0000)) @@ -158,13 +159,36 @@ void asm_xtensa_j_label(asm_xtensa_t *as, uint label) { asm_xtensa_op_j(as, rel); } +static bool calculate_branch_displacement(asm_xtensa_t *as, uint label, ptrdiff_t *displacement) { + assert(displacement != NULL && "Displacement pointer is NULL"); + + uint32_t label_offset = get_label_dest(as, label); + *displacement = (ptrdiff_t)(label_offset - as->base.code_offset - 4); + return (label_offset != (uint32_t)-1) && (*displacement < 0); +} + void asm_xtensa_bccz_reg_label(asm_xtensa_t *as, uint cond, uint reg, uint label) { - uint32_t dest = get_label_dest(as, label); - int32_t rel = dest - as->base.code_offset - 4; - if (as->base.pass == MP_ASM_PASS_EMIT && !SIGNED_FIT12(rel)) { + ptrdiff_t rel = 0; + bool can_emit_short_jump = calculate_branch_displacement(as, label, &rel); + + if (can_emit_short_jump && SIGNED_FIT12(rel)) { + // Backwards BCCZ opcodes with an offset that fits in 12 bits can + // be emitted without any change. + asm_xtensa_op_bccz(as, cond, reg, rel); + return; + } + + // Range is effectively extended to 18 bits, as a more complex jump code + // sequence is emitted. + if (as->base.pass == MP_ASM_PASS_EMIT && !SIGNED_FIT18(rel - 6)) { mp_raise_msg_varg(&mp_type_RuntimeError, ET_OUT_OF_RANGE, MP_QSTR_bccz); } - asm_xtensa_op_bccz(as, cond, reg, rel); + + // ~BCCZ skip ; +0 <- Condition is flipped here (EQ -> NE, etc.) + // J addr ; +3 + // skip: ; +6 + asm_xtensa_op_bccz(as, cond ^ 1, reg, 6 - 4); + asm_xtensa_op_j(as, rel - 3); } void asm_xtensa_bcc_reg_reg_label(asm_xtensa_t *as, uint cond, uint reg1, uint reg2, uint label) { |