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From: Morten Sylvest Olsen <pbk1105@pbk.dk>
To: <gcc-help@gcc.gnu.org>
Subject: sibling call optimization
Date: Mon, 22 Oct 2001 05:35:00 -0000	[thread overview]
Message-ID: <Pine.LNX.4.33.0110221431190.15752-100000@venus.pbk.dk> (raw)

Hi all..

I'm trying to make a sibling call (or, rather making the GCC optimizer
make one) through a function pointer. This seems to be impossible?

I've read some old messages about the tailcall/siblingcalls that talked
about implementing an explicit __attribute__ or similar construct to tell
gcc to make a sibling call. This was never implemented, or?

Without knowing much about gcc internals, it seems to be this part of
gcc/calls.c responsible:

      /* If the register holding the address is a callee saved
	 register, then we lose.  We have no way to prevent that,
	 so we only allow calls to named functions.  */
      /* ??? This could be done by having the insn constraints
	 use a register class that is all call-clobbered.  Any
	 reload insns generated to fix things up would appear
	 before the sibcall_epilogue.  */
      || fndecl == NULL_TREE

Or maybe not, I've only looked at it very briefly.

- Morten

The only perfect science is hind-sight.

                 reply	other threads:[~2001-10-22  5:35 UTC|newest]

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