Hi Jim,
>>> But my return label is getting optimized away. Could you please tell
>>> me how to avoid this.
>
>You may also need to add a (USE (REG RA)) to the call pattern. Gcc
will see that you set a register to the value of the
>return label, but it won't see any code that uses that register, so it
will optimize away both the load and the label. To
>prevent this, you need to add an explicit use of that register to the
call insn pattern.
I have that.. :). Here is the pattern for the call_insn produced.
(define_insn "brc_call_simulate"
[(call (mem:HI (match_operand 0 "register_operand" "r"))
(match_operand 1 "" "i"))
(use (reg:HI 7))
(clobber (reg:HI 7))]
""
"jr\t%0")
But GCC is not optimizing the load away. Its just the the return label
that gets optimized away.
CMIIW, I think the problem is this :
1. The label output is local to this function
2. The label creates a new basic block. There is no jump to this label.
As a result, there is only
one incoming edge to this block and that is the fall through edge after
the return from the call.
3. As a result, GCC tries to merge those two blocks and in the process
removes the label.
How do I prevent this ?
Thanks in advance,
Kunal
