stage1 vm abi更新 修复更多问题

stage0/spl_mcode.h

@@ -115,38 +115,26 @@ typedef enum {
  *   [strtab]      each: slen, str(pad8)
  *   [gdata]       each: dsize(8), data(dsize bytes, padded to 8)
  *
- * === Calling Convention ===
+ * === Aggregate Return ABI (sret) ===
+ *
+ * 凡返回值类型为聚合（struct / union / enum / array / shape），
+ * 采用调用者分配 / 被调用者填充的间接返回约定：
  *
  * Before CALL:
- *   - args pushed left-to-right
- *   - target address pushed last
+ *   - caller 在自己的帧里 alloca 一块 RetTy 大小的空间
+ *   - 该空间的地址作为第 0 个实参先压栈
+ *   - 其余实参照常从左到右压栈
+ *   - target 地址最后压栈
+ *   - CALL imm = 普通实参个数 + 1
  *
- * CALL (imm = nargs):
- *   1. pop target address
- *   2. callstack[cp++] = {saved_fp, saved_ip, nargs}
- *   3. fp = sp - nargs    (fp points to arg0)
- *   4. ip = target address
+ * Callee 进入后:
+ *   - fp+0 存放 sret 指针
+ *   - 形参 i 位于 fp + 8*(i+1)
+ *   - 返回值直接写入 *(fp+0)，然后执行 RET void
  *
- * ALLOC k:
- *   sp += k  (slots zeroed; local[j] = stacks.data[fp + nargs + j])
- *
- * LADDR imm:
- *   push &stacks.data[fp + imm]
- *   (imm < nargs accesses args; imm >= nargs accesses locals)
- *
- * GADDR imm:
- *   push prog->gdata[imm]  (pointer to global data blob)
- *
- * RET:
- *   1. pop retval if non-void type
- *   2. sp = fp
- *   3. pop frame; fp = saved_fp, ip = saved_ip
- *   4. push retval if non-void type
- *
- * CALLI (indirect call):
- *   - stack before:  ..., arg0, ..., argN-1, nargs, func_addr
- *   1. pop func_addr, then pop nargs
- *   2. same as CALL steps 2-4
+ * Caller 侧:
+ *   - 调用完成后，CALL 结果槽保存 sret 指针；
+ *     后续对聚合值的所有读取都通过该指针进行
  */
 
 #define SPL_BINFMT_MAGIC "SPLBIN\0\0"