void
reemit_insn_block_notes (void)
{
tree cur_block = DECL_INITIAL (cfun->decl);
rtx insn, note;
insn = get_insns ();
if (!active_insn_p (insn))
insn = next_active_insn (insn);
for (; insn; insn = next_active_insn (insn))
{
tree this_block;
/* Avoid putting scope notes between jump table and its label. */
if (JUMP_P (insn)
&& (GET_CODE (PATTERN (insn)) == ADDR_VEC
|| GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC))
continue;
this_block = insn_scope (insn);
/* For sequences compute scope resulting from merging all scopes
of instructions nested inside. */
if (GET_CODE (PATTERN (insn)) == SEQUENCE)
{
int i;
rtx body = PATTERN (insn);
this_block = NULL;
for (i = 0; i < XVECLEN (body, 0); i++)
this_block = choose_inner_scope (this_block,
insn_scope (XVECEXP (body, 0, i)));
}
if (! this_block)
continue;
if (this_block != cur_block)
{
change_scope (insn, cur_block, this_block);
cur_block = this_block;
}
}
/* change_scope emits before the insn, not after. */
note = emit_note (NOTE_INSN_DELETED);
change_scope (note, cur_block, DECL_INITIAL (cfun->decl));
delete_insn (note);
reorder_blocks ();
}
void
optimize_sibling_and_tail_recursive_calls (void)
{
rtx insn, insns;
basic_block alternate_exit = EXIT_BLOCK_PTR;
bool no_sibcalls_this_function = false;
bool successful_replacement = false;
bool replaced_call_placeholder = false;
edge e;
insns = get_insns ();
cleanup_cfg (CLEANUP_PRE_SIBCALL | CLEANUP_PRE_LOOP);
/* If there are no basic blocks, then there is nothing to do. */
if (n_basic_blocks == 0)
return;
/* If we are using sjlj exceptions, we may need to add a call to
_Unwind_SjLj_Unregister at exit of the function. Which means
that we cannot do any sibcall transformations. */
if (USING_SJLJ_EXCEPTIONS && current_function_has_exception_handlers ())
no_sibcalls_this_function = true;
return_value_pseudo = NULL_RTX;
/* Find the exit block.
It is possible that we have blocks which can reach the exit block
directly. However, most of the time a block will jump (or fall into)
N_BASIC_BLOCKS - 1, which in turn falls into the exit block. */
for (e = EXIT_BLOCK_PTR->pred;
e && alternate_exit == EXIT_BLOCK_PTR;
e = e->pred_next)
{
rtx insn;
if (e->dest != EXIT_BLOCK_PTR || e->succ_next != NULL)
continue;
/* Walk forwards through the last normal block and see if it
does nothing except fall into the exit block. */
for (insn = BB_HEAD (EXIT_BLOCK_PTR->prev_bb);
insn;
insn = NEXT_INSN (insn))
{
rtx set;
/* This should only happen once, at the start of this block. */
if (GET_CODE (insn) == CODE_LABEL)
continue;
if (GET_CODE (insn) == NOTE)
continue;
if (GET_CODE (insn) == INSN
&& GET_CODE (PATTERN (insn)) == USE)
continue;
/* Exit block also may contain copy from pseudo containing
return value to hard register. */
if (GET_CODE (insn) == INSN
&& (set = single_set (insn))
&& SET_DEST (set) == current_function_return_rtx
&& REG_P (SET_SRC (set))
&& !return_value_pseudo)
{
return_value_pseudo = SET_SRC (set);
continue;
}
break;
}
/* If INSN is zero, then the search walked all the way through the
block without hitting anything interesting. This block is a
valid alternate exit block. */
if (insn == NULL)
alternate_exit = e->src;
else
return_value_pseudo = NULL;
}
/* If the function uses ADDRESSOF, we can't (easily) determine
at this point if the value will end up on the stack. */
no_sibcalls_this_function |= sequence_uses_addressof (insns);
/* Walk the insn chain and find any CALL_PLACEHOLDER insns. We need to
select one of the insn sequences attached to each CALL_PLACEHOLDER.
The different sequences represent different ways to implement the call,
ie, tail recursion, sibling call or normal call.
Since we do not create nested CALL_PLACEHOLDERs, the scan
continues with the insn that was after a replaced CALL_PLACEHOLDER;
we don't rescan the replacement insns. */
for (insn = insns; insn; insn = NEXT_INSN (insn))
{
if (GET_CODE (insn) == CALL_INSN
&& GET_CODE (PATTERN (insn)) == CALL_PLACEHOLDER)
{
int sibcall = (XEXP (PATTERN (insn), 1) != NULL_RTX);
int tailrecursion = (XEXP (PATTERN (insn), 2) != NULL_RTX);
basic_block call_block = BLOCK_FOR_INSN (insn);
/* alloca (until we have stack slot life analysis) inhibits
sibling call optimizations, but not tail recursion.
Similarly if we use varargs or stdarg since they implicitly
may take the address of an argument. */
if (current_function_calls_alloca || current_function_stdarg)
sibcall = 0;
/* 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. */
if (no_sibcalls_this_function
/* ??? Overly conservative. */
|| frame_offset
/* Any function that calls setjmp might have longjmp called from
any called function. ??? We really should represent this
properly in the CFG so that this needn't be special cased. */
|| current_function_calls_setjmp
/* Can't if more than one successor or single successor is not
exit block. These two tests prevent tail call optimization
in the presence 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)
/* 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, BB_END (call_block)))
sibcall = 0, tailrecursion = 0;
/* Select a set of insns to implement the call and emit them.
Tail recursion is the most efficient, so select it over
a tail/sibling call. */
if (sibcall || tailrecursion)
successful_replacement = true;
replaced_call_placeholder = true;
replace_call_placeholder (insn,
tailrecursion != 0
? sibcall_use_tail_recursion
: sibcall != 0
? sibcall_use_sibcall
: sibcall_use_normal);
}
}
if (successful_replacement)
{
rtx insn;
tree arg;
/* A sibling call sequence invalidates any REG_EQUIV notes made for
this function's incoming arguments.
At the start of RTL generation we know the only REG_EQUIV notes
in the rtl chain are those for incoming arguments, so we can safely
flush any REG_EQUIV note.
This is (slight) overkill. We could keep track of the highest
argument we clobber and be more selective in removing notes, but it
does not seem to be worth the effort. */
purge_reg_equiv_notes ();
/* A sibling call sequence also may invalidate RTX_UNCHANGING_P
flag of some incoming arguments MEM RTLs, because it can write into
those slots. We clear all those bits now.
This is (slight) overkill, we could keep track of which arguments
we actually write into. */
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
{
if (INSN_P (insn))
purge_mem_unchanging_flag (PATTERN (insn));
}
/* Similarly, invalidate RTX_UNCHANGING_P for any incoming
arguments passed in registers. */
for (arg = DECL_ARGUMENTS (current_function_decl);
arg;
arg = TREE_CHAIN (arg))
{
if (REG_P (DECL_RTL (arg)))
RTX_UNCHANGING_P (DECL_RTL (arg)) = false;
}
}
/* There may have been NOTE_INSN_BLOCK_{BEGIN,END} notes in the
CALL_PLACEHOLDER alternatives that we didn't emit. Rebuild the
lexical block tree to correspond to the notes that still exist. */
if (replaced_call_placeholder)
reorder_blocks ();
/* This information will be invalid after inline expansion. Kill it now. */
free_basic_block_vars (0);
free_EXPR_LIST_list (&tail_recursion_label_list);
}
