+/* Return the number of a YMODE register to which
+
+ (subreg:YMODE (reg:XMODE XREGNO) OFFSET)
+
+ can be simplified. Return -1 if the subreg can't be simplified.
+
+ XREGNO is a hard register number. */
+
+int
+simplify_subreg_regno (unsigned int xregno, enum machine_mode xmode,
+ unsigned int offset, enum machine_mode ymode)
+{
+ struct subreg_info info;
+ unsigned int yregno;
+
+#ifdef CANNOT_CHANGE_MODE_CLASS
+ /* Give the backend a chance to disallow the mode change. */
+ if (GET_MODE_CLASS (xmode) != MODE_COMPLEX_INT
+ && GET_MODE_CLASS (xmode) != MODE_COMPLEX_FLOAT
+ && REG_CANNOT_CHANGE_MODE_P (xregno, xmode, ymode))
+ return -1;
+#endif
+
+ /* We shouldn't simplify stack-related registers. */
+ if ((!reload_completed || frame_pointer_needed)
+ && (xregno == FRAME_POINTER_REGNUM
+ || xregno == HARD_FRAME_POINTER_REGNUM))
+ return -1;
+
+ if (FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
+ && xregno == ARG_POINTER_REGNUM)
+ return -1;
+
+ if (xregno == STACK_POINTER_REGNUM)
+ return -1;
+
+ /* Try to get the register offset. */
+ subreg_get_info (xregno, xmode, offset, ymode, &info);
+ if (!info.representable_p)
+ return -1;
+
+ /* Make sure that the offsetted register value is in range. */
+ yregno = xregno + info.offset;
+ if (!HARD_REGISTER_NUM_P (yregno))
+ return -1;
+
+ /* See whether (reg:YMODE YREGNO) is valid.
+
+ ??? We allow invalid registers if (reg:XMODE XREGNO) is also invalid.
+ This is a kludge to work around how float/complex arguments are passed
+ on 32-bit SPARC and should be fixed. */
+ if (!HARD_REGNO_MODE_OK (yregno, ymode)
+ && HARD_REGNO_MODE_OK (xregno, xmode))
+ return -1;
+
+ return (int) yregno;
+}
+