static int
try_apply_stack_adjustment (rtx insn, struct csa_reflist *reflist,
HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta)
{
struct csa_reflist *ml;
rtx set;
set = single_set_for_csa (insn);
if (MEM_P (SET_DEST (set)))
validate_change (insn, &SET_DEST (set),
replace_equiv_address (SET_DEST (set), stack_pointer_rtx),
1);
else
validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1);
for (ml = reflist; ml ; ml = ml->next)
{
rtx new_addr = plus_constant (Pmode, stack_pointer_rtx,
ml->sp_offset - delta);
rtx new_val;
if (MEM_P (*ml->ref))
new_val = replace_equiv_address_nv (*ml->ref, new_addr);
else if (GET_MODE (*ml->ref) == GET_MODE (stack_pointer_rtx))
new_val = new_addr;
else
new_val = lowpart_subreg (GET_MODE (*ml->ref), new_addr,
GET_MODE (new_addr));
validate_change (ml->insn, ml->ref, new_val, 1);
}
if (apply_change_group ())
{
/* Succeeded. Update our knowledge of the stack references. */
for (ml = reflist; ml ; ml = ml->next)
ml->sp_offset -= delta;
return 1;
}
else
return 0;
}
static void
combine_stack_adjustments_for_block (basic_block bb)
{
HOST_WIDE_INT last_sp_adjust = 0;
rtx last_sp_set = NULL_RTX;
struct csa_memlist *memlist = NULL;
rtx insn, next, set;
struct record_stack_memrefs_data data;
bool end_of_block = false;
for (insn = BB_HEAD (bb); !end_of_block ; insn = next)
{
end_of_block = insn == BB_END (bb);
next = NEXT_INSN (insn);
if (! INSN_P (insn))
continue;
set = single_set_for_csa (insn);
if (set)
{
rtx dest = SET_DEST (set);
rtx src = SET_SRC (set);
/* Find constant additions to the stack pointer. */
if (dest == stack_pointer_rtx
&& GET_CODE (src) == PLUS
&& XEXP (src, 0) == stack_pointer_rtx
&& GET_CODE (XEXP (src, 1)) == CONST_INT)
{
HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1));
/* If we've not seen an adjustment previously, record
it now and continue. */
if (! last_sp_set)
{
last_sp_set = insn;
last_sp_adjust = this_adjust;
continue;
}
/* If not all recorded memrefs can be adjusted, or the
adjustment is now too large for a constant addition,
we cannot merge the two stack adjustments.
Also we need to be careful to not move stack pointer
such that we create stack accesses outside the allocated
area. We can combine an allocation into the first insn,
or a deallocation into the second insn. We can not
combine an allocation followed by a deallocation.
The only somewhat frequent occurrence of the later is when
a function allocates a stack frame but does not use it.
For this case, we would need to analyze rtl stream to be
sure that allocated area is really unused. This means not
only checking the memory references, but also all registers
or global memory references possibly containing a stack
frame address.
Perhaps the best way to address this problem is to teach
gcc not to allocate stack for objects never used. */
/* Combine an allocation into the first instruction. */
if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0)
{
if (try_apply_stack_adjustment (last_sp_set, memlist,
last_sp_adjust + this_adjust,
this_adjust))
{
/* It worked! */
delete_insn (insn);
last_sp_adjust += this_adjust;
continue;
}
}
/* Otherwise we have a deallocation. Do not combine with
a previous allocation. Combine into the second insn. */
else if (STACK_GROWS_DOWNWARD
? last_sp_adjust >= 0 : last_sp_adjust <= 0)
{
if (try_apply_stack_adjustment (insn, memlist,
last_sp_adjust + this_adjust,
-last_sp_adjust))
{
/* It worked! */
delete_insn (last_sp_set);
last_sp_set = insn;
last_sp_adjust += this_adjust;
free_csa_memlist (memlist);
memlist = NULL;
continue;
}
}
/* Combination failed. Restart processing from here. If
deallocation+allocation conspired to cancel, we can
delete the old deallocation insn. */
if (last_sp_set && last_sp_adjust == 0)
delete_insn (insn);
free_csa_memlist (memlist);
memlist = NULL;
last_sp_set = insn;
last_sp_adjust = this_adjust;
continue;
}
/* Find a predecrement of exactly the previous adjustment and
turn it into a direct store. Obviously we can't do this if
there were any intervening uses of the stack pointer. */
if (memlist == NULL
&& MEM_P (dest)
&& ((GET_CODE (XEXP (dest, 0)) == PRE_DEC
&& (last_sp_adjust
== (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))))
|| (GET_CODE (XEXP (dest, 0)) == PRE_MODIFY
&& GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS
&& XEXP (XEXP (XEXP (dest, 0), 1), 0) == stack_pointer_rtx
&& (GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1))
== CONST_INT)
&& (INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1))
== -last_sp_adjust)))
&& XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
&& ! reg_mentioned_p (stack_pointer_rtx, src)
&& memory_address_p (GET_MODE (dest), stack_pointer_rtx)
&& validate_change (insn, &SET_DEST (set),
replace_equiv_address (dest,
stack_pointer_rtx),
0))
{
delete_insn (last_sp_set);
free_csa_memlist (memlist);
memlist = NULL;
last_sp_set = NULL_RTX;
last_sp_adjust = 0;
continue;
}
}
data.insn = insn;
data.memlist = memlist;
if (!CALL_P (insn) && last_sp_set
&& !for_each_rtx (&PATTERN (insn), record_stack_memrefs, &data))
{
memlist = data.memlist;
continue;
}
memlist = data.memlist;
/* Otherwise, we were not able to process the instruction.
Do not continue collecting data across such a one. */
if (last_sp_set
&& (CALL_P (insn)
|| reg_mentioned_p (stack_pointer_rtx, PATTERN (insn))))
{
if (last_sp_set && last_sp_adjust == 0)
delete_insn (last_sp_set);
free_csa_memlist (memlist);
memlist = NULL;
last_sp_set = NULL_RTX;
last_sp_adjust = 0;
}
}
if (last_sp_set && last_sp_adjust == 0)
delete_insn (last_sp_set);
if (memlist)
free_csa_memlist (memlist);
}
