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Commit e5c617ff by Richard Kenner Committed by Richard Kenner
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sibcall.c (call_ends_block_p): New function. 

	* sibcall.c (call_ends_block_p): New function.
	(optimize_sibling_and_tail_recursive_call): Use it.

From-SVN: r39879
parent 2091638a
Showing with 69 additions and 54 deletions
gcc/ChangeLog
Mon Feb 19 08:27:21 2001 Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
* sibcall.c (call_ends_block_p): New function.
(optimize_sibling_and_tail_recursive_call): Use it.
2001-02-18 Kazu Hirata <kazu@hxi.com>
* config/h8300/h8300.md: Update copyright.
......
gcc/sibcall.c
/* Generic sibling call optimization support
Copyright (C) 1999, 2000 Free Software Foundation, Inc.
Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
This file is part of GNU CC.
......@@ -38,6 +38,7 @@ static rtx skip_use_of_return_value PARAMS ((rtx, enum rtx_code));
static rtx skip_stack_adjustment PARAMS ((rtx));
static rtx skip_pic_restore PARAMS ((rtx));
static rtx skip_jump_insn PARAMS ((rtx));
static int call_ends_block_p PARAMS ((rtx, rtx));
static int uses_addressof PARAMS ((rtx));
static int sequence_uses_addressof PARAMS ((rtx));
static void purge_reg_equiv_notes PARAMS ((void));
......@@ -255,6 +256,52 @@ skip_jump_insn (orig_insn)
return orig_insn;
}
/* Using the above functions, see if INSN, skipping any of the above,
goes all the way to END, the end of a basic block. Return 1 if so. */
static int
call_ends_block_p (insn, end)
rtx insn;
rtx end;
{
rtx hardret, softret;
/* END might be a note, so get the last nonnote insn of the block. */
end = next_nonnote_insn (PREV_INSN (end));
/* If the call was the end of the block, then we're OK. */
if (insn == end)
return 1;
/* Skip over copying from the call's return value pseudo into
this function's hard return register and if that's the end
of the block, we're OK. */
identify_call_return_value (PATTERN (insn), &hardret, &softret);
insn = skip_copy_to_return_value (insn, hardret, softret);
if (insn == end)
return 1;
/* Skip any stack adjustment. */
insn = skip_stack_adjustment (insn);
if (insn == end)
return 1;
/* Skip over a CLOBBER of the return value as a hard reg. */
insn = skip_use_of_return_value (insn, CLOBBER);
if (insn == end)
return 1;
/* Skip over a USE of the return value (as a hard reg). */
insn = skip_use_of_return_value (insn, USE);
if (insn == end)
return 1;
/* Skip over a JUMP_INSN at the end of the block. If that doesn't end the
block, the original CALL_INSN didn't. */
insn = skip_jump_insn (insn);
return insn == end;
}
/* Scan the rtx X for ADDRESSOF expressions or
current_function_internal_arg_pointer registers.
......@@ -533,18 +580,7 @@ optimize_sibling_and_tail_recursive_calls ()
{
int sibcall = (XEXP (PATTERN (insn), 1) != NULL_RTX);
int tailrecursion = (XEXP (PATTERN (insn), 2) != NULL_RTX);
basic_block call_block;
rtx end, temp, hardret, softret;
/* We must be careful with stack slots which are live at
potential optimization sites.
?!? This test is overly conservative and will be replaced. */
if (frame_offset
/* Taking the address of a local variable is fatal to tail
recursion if the address is used by the recursive call. */
|| current_function_uses_addressof)
sibcall = 0, tailrecursion = 0;
basic_block call_block = BLOCK_FOR_INSN (insn);
/* alloca (until we have stack slot life analysis) inhibits
sibling call optimizations, but not tail recursion.
......@@ -554,49 +590,23 @@ optimize_sibling_and_tail_recursive_calls ()
|| current_function_varargs || current_function_stdarg)
sibcall = 0;
/* Get the block for the call and the last non-note insn in it. We
take advantage of the fact that this cannot be the exit block. */
call_block = BLOCK_FOR_INSN (insn);
end = prev_nonnote_insn (NEXT_INSN (call_block->end));
/* If the block has more than one successor, then we can not
perform sibcall or tail recursion optimizations. If the single
successor is not the exit block, then we can not perform sibcall
or tail recursion optimizations. Note that these two tests
combined are sufficient to prevent tail call optimization in the
presense of active exception handlers. */
if (call_block->succ == NULL
/* See if there are any reasons we can't perform either sibling or
tail call optimizations. We must be careful with stack slots
which are live at potential optimization sites. ?!? This test
is overly conservative and will be replaced. */
if (frame_offset
/* Can't take address of local var if used by recursive call. */
|| current_function_uses_addressof
/* Can't if more than one successor or single successor is not
exit block. These two tests prevent tail call optimization
in the presense of active exception handlers. */
|| call_block->succ == NULL
|| call_block->succ->succ_next != NULL
|| (call_block->succ->dest != EXIT_BLOCK_PTR
&& call_block->succ->dest != alternate_exit))
sibcall = 0, tailrecursion = 0;
/* If we haven't failed yet, check if this (or safe things) ends our
block. */
if ((sibcall || tailrecursion)
/* If the call was the end of the block, then we're OK. */
&& (end == (temp = insn)
/* Skip over copying from the call's return value pseudo into
this function's hard return register and if that's the end
of the block, we're OK. */
|| (identify_call_return_value (PATTERN (insn), &hardret,
&softret)
&& end == (temp = skip_copy_to_return_value (insn,
hardret,
softret)))
/* Skip any stack adjustment. */
|| end == (temp = skip_stack_adjustment (temp))
/* Skip over a CLOBBER of the return value as a hard reg. */
|| end == (temp = skip_use_of_return_value (temp, CLOBBER))
/* Skip over a USE of the return value (as a hard reg). */
|| end == (temp = skip_use_of_return_value (temp, USE))
/* Skip over the JUMP_INSN at the end of the block. */
|| end == (temp = skip_jump_insn (temp))))
;
else
/* There are operations at the end of the block which we must
execute after returning from the function call. So this call
can not be optimized. */
&& call_block->succ->dest != alternate_exit)
/* If this call doesn't end the block, there are operations at
the end of the block which we must execute after returning. */
|| ! call_ends_block_p (insn, call_block->end))
sibcall = 0, tailrecursion = 0;
/* Select a set of insns to implement the call and emit them.
......
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