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riscv-gcc-1
Commit e304a8e6 by Michael Hayes Committed by Michael Hayes
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loop.c (loop_giv_reduce_benefit): Break out from strength_reduce. 

	* loop.c (loop_giv_reduce_benefit): Break out from strength_reduce.
	(loop_givs_dead_check, loop_givs_reduce, loop_givs_rescan): Likewise.
	(prescan_loop): Set pre_header_has_call in loop_info.
	* loop.h (struct_iv_class): Add `final_value' and `all_reduced'.
	(struct loop_info): Add `pre_header_has_call'.

From-SVN: r38578
parent 6ec73c7c
Showing with 498 additions and 458 deletions
gcc/ChangeLog
2001-01-01 Michael Hayes <mhayes@redhat.com>
* loop.c (loop_giv_reduce_benefit): Break out from strength_reduce.
(loop_givs_dead_check, loop_givs_reduce, loop_givs_rescan): Likewise.
(prescan_loop): Set pre_header_has_call in loop_info.
* loop.h (struct_iv_class): Add `final_value' and `all_reduced'.
(struct loop_info): Add `pre_header_has_call'.
2001-01-01 Michael Hayes <mhayes@redhat.com>
* loop.c (loop_bivs_find): Break out from strength_reduce.
(loop_bivs_init_find, loop_bivs_check, loop_givs_find): Likewise.
(loop_givs_check, loop_biv_eliminable_p): Likewise.
......
gcc/loop.c
......@@ -186,8 +186,14 @@ static void loop_bivs_init_find PARAMS((struct loop *));
static void loop_bivs_check PARAMS((struct loop *));
static void loop_givs_find PARAMS((struct loop *));
static void loop_givs_check PARAMS((struct loop *));
static void loop_biv_eliminable_p PARAMS((struct loop *, struct iv_class *,
static int loop_biv_eliminable_p PARAMS((struct loop *, struct iv_class *,
int, int));
static int loop_giv_reduce_benefit PARAMS((struct loop *, struct iv_class *,
struct induction *, rtx));
static void loop_givs_dead_check PARAMS((struct loop *, struct iv_class *));
static void loop_givs_reduce PARAMS((struct loop *, struct iv_class *));
static void loop_givs_rescan PARAMS((struct loop *, struct iv_class *,
rtx *, rtx));
static void strength_reduce PARAMS ((struct loop *, int, int));
static void find_single_use_in_loop PARAMS ((rtx, rtx, varray_type));
static int valid_initial_value_p PARAMS ((rtx, rtx, int, rtx));
......@@ -2301,6 +2307,7 @@ prescan_loop (loop)
rtx exit_target = next_nonnote_insn (end);
loop_info->has_indirect_jump = indirect_jump_in_function;
loop_info->pre_header_has_call = 0;
loop_info->has_call = 0;
loop_info->has_volatile = 0;
loop_info->has_tablejump = 0;
......@@ -2314,6 +2321,17 @@ prescan_loop (loop)
loop_info->mems_idx = 0;
loop_info->num_mem_sets = 0;
for (insn = start; insn && GET_CODE (insn) != CODE_LABEL;
insn = PREV_INSN (insn))
{
if (GET_CODE (insn) == CALL_INSN)
{
loop_info->pre_header_has_call = 1;
break;
}
}
for (insn = NEXT_INSN (start); insn != NEXT_INSN (end);
insn = NEXT_INSN (insn))
{
......@@ -3692,18 +3710,20 @@ static void
loop_bivs_init_find (loop)
struct loop *loop;
{
struct loop_info *loop_info = LOOP_INFO (loop);
struct loop_ivs *ivs = LOOP_IVS (loop);
/* Temporary list pointers for traversing ivs->loop_iv_list. */
struct iv_class *bl;
basic_block ebb;
int call_seen;
rtx p;
/* Find initial value for each biv by searching backwards from loop_start,
halting at first label. Also record any test condition. */
call_seen = 0;
for (p = loop_start; p && GET_CODE (p) != CODE_LABEL; p = PREV_INSN (p))
for (p = loop->start; p && GET_CODE (p) != CODE_LABEL; p = PREV_INSN (p))
{
rtx test;
note_insn = p;
if (GET_CODE (p) == CALL_INSN)
......@@ -3717,12 +3737,12 @@ loop_bivs_init_find (loop)
constants and registers and only certain of those. */
if (GET_CODE (p) == JUMP_INSN
&& JUMP_LABEL (p) != 0
&& next_real_insn (JUMP_LABEL (p)) == next_real_insn (loop_end)
&& next_real_insn (JUMP_LABEL (p)) == next_real_insn (loop->end)
&& (test = get_condition_for_loop (loop, p)) != 0
&& GET_CODE (XEXP (test, 0)) == REG
&& REGNO (XEXP (test, 0)) < max_reg_before_loop
&& (bl = ivs->reg_biv_class[REGNO (XEXP (test, 0))]) != 0
&& valid_initial_value_p (XEXP (test, 1), p, call_seen, loop_start)
&& valid_initial_value_p (XEXP (test, 1), p, call_seen, loop->start)
&& bl->init_insn == 0)
{
/* If an NE test, we have an initial value! */
......@@ -3776,7 +3796,9 @@ loop_bivs_check (loop)
if ((GET_MODE (src) == GET_MODE (regno_reg_rtx[bl->regno])
|| GET_MODE (src) == VOIDmode)
&& valid_initial_value_p (loop, src, bl->init_insn))
&& valid_initial_value_p (src, bl->init_insn,
LOOP_INFO (loop)->pre_header_has_call,
loop->start))
{
bl->initial_value = src;
......@@ -3835,308 +3857,209 @@ loop_givs_check (loop)
}
static void
/* Return non-zero if it is possible to eliminate the biv BL provided
all givs are reduced. This is possible if either the reg is not
used outside the loop, or we can compute what its final value will
be. */
static int
loop_biv_eliminable_p (loop, bl, threshold, insn_count)
struct loop *loop;
struct iv_class *bl;
int threshold;
int insn_count;
{
/* Test whether it will be possible to eliminate this biv
provided all givs are reduced. This is possible if either
the reg is not used outside the loop, or we can compute
what its final value will be.
/* For architectures with a decrement_and_branch_until_zero insn,
don't do this if we put a REG_NONNEG note on the endtest for this
biv. */
For architectures with a decrement_and_branch_until_zero insn,
don't do this if we put a REG_NONNEG note on the endtest for
this biv. */
#ifdef HAVE_decrement_and_branch_until_zero
if (bl->nonneg)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Cannot eliminate nonneg biv %d.\n", bl->regno);
return 0;
}
#endif
/* Compare against bl->init_insn rather than loop_start.
We aren't concerned with any uses of the biv between
init_insn and loop_start since these won't be affected
by the value of the biv elsewhere in the function, so
long as init_insn doesn't use the biv itself.
March 14, 1989 -- self@bayes.arc.nasa.gov */
/* Check that biv is used outside loop or if it has a final value.
Compare against bl->init_insn rather than loop->start. We aren't
concerned with any uses of the biv between init_insn and
loop->start since these won't be affected by the value of the biv
elsewhere in the function, so long as init_insn doesn't use the
biv itself. */
if ((REGNO_LAST_LUID (bl->regno) < INSN_LUID (loop->end)
&& bl->init_insn
&& INSN_UID (bl->init_insn) < max_uid_for_loop
&& REGNO_FIRST_LUID (bl->regno) >= INSN_LUID (bl->init_insn)
#ifdef HAVE_decrement_and_branch_until_zero
&& ! bl->nonneg
#endif
&& ! reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
|| ((final_value = final_biv_value (loop, bl))
#ifdef HAVE_decrement_and_branch_until_zero
&& ! bl->nonneg
#endif
))
|| (bl->final_value = final_biv_value (loop, bl)))
return maybe_eliminate_biv (loop, bl, 0, threshold, insn_count);
else
if (loop_dump_stream)
{
fprintf (loop_dump_stream,
"Cannot eliminate biv %d.\n",
bl->regno);
fprintf (loop_dump_stream,
"First use: insn %d, last use: insn %d.\n",
REGNO_FIRST_UID (bl->regno),
REGNO_LAST_UID (bl->regno));
}
return 0;
}
/* Perform strength reduction and induction variable elimination.
Pseudo registers created during this function will be beyond the
last valid index in several tables including regs->n_times_set and
regno_last_uid. This does not cause a problem here, because the
added registers cannot be givs outside of their loop, and hence
will never be reconsidered. But scan_loop must check regnos to
make sure they are in bounds. */
/* Reduce each giv of BL that we have decided to reduce. */
static void
strength_reduce (loop, insn_count, flags)
loop_givs_reduce (loop, bl)
struct loop *loop;
int insn_count;
int flags;
struct iv_class *bl;
{
struct loop_info *loop_info = LOOP_INFO (loop);
struct loop_regs *regs = LOOP_REGS (loop);
struct loop_ivs *ivs = LOOP_IVS (loop);
rtx p;
/* Temporary list pointers for traversing ivs->loop_iv_list. */
struct iv_class *bl, **backbl;
/* Ratio of extra register life span we can justify
for saving an instruction. More if loop doesn't call subroutines
since in that case saving an insn makes more difference
and more registers are available. */
/* ??? could set this to last value of threshold in move_movables */
int threshold = (loop_info->has_call ? 1 : 2) * (3 + n_non_fixed_regs);
/* Map of pseudo-register replacements. */
rtx *reg_map = NULL;
int reg_map_size;
int call_seen;
rtx test;
rtx end_insert_before;
int unrolled_insn_copies = 0;
rtx loop_start = loop->start;
rtx loop_end = loop->end;
rtx test_reg = gen_rtx_REG (word_mode, LAST_VIRTUAL_REGISTER + 1);
struct induction *v;
addr_placeholder = gen_reg_rtx (Pmode);
for (v = bl->giv; v; v = v->next_iv)
{
struct induction *tv;
if (! v->ignore && v->same == 0)
{
int auto_inc_opt = 0;
/* Save insn immediately after the loop_end. Insns inserted after loop_end
must be put before this insn, so that they will appear in the right
order (i.e. loop order).
/* If the code for derived givs immediately below has already
allocated a new_reg, we must keep it. */
if (! v->new_reg)
v->new_reg = gen_reg_rtx (v->mode);
If loop_end is the end of the current function, then emit a
NOTE_INSN_DELETED after loop_end and set end_insert_before to the
dummy note insn. */
if (NEXT_INSN (loop_end) != 0)
end_insert_before = NEXT_INSN (loop_end);
else
end_insert_before = emit_note_after (NOTE_INSN_DELETED, loop_end);
#ifdef AUTO_INC_DEC
/* If the target has auto-increment addressing modes, and
this is an address giv, then try to put the increment
immediately after its use, so that flow can create an
auto-increment addressing mode. */
if (v->giv_type == DEST_ADDR && bl->biv_count == 1
&& bl->biv->always_executed && ! bl->biv->maybe_multiple
/* We don't handle reversed biv's because bl->biv->insn
does not have a valid INSN_LUID. */
&& ! bl->reversed
&& v->always_executed && ! v->maybe_multiple
&& INSN_UID (v->insn) < max_uid_for_loop)
{
/* If other giv's have been combined with this one, then
this will work only if all uses of the other giv's occur
before this giv's insn. This is difficult to check.
We simplify this by looking for the common case where
there is one DEST_REG giv, and this giv's insn is the
last use of the dest_reg of that DEST_REG giv. If the
increment occurs after the address giv, then we can
perform the optimization. (Otherwise, the increment
would have to go before other_giv, and we would not be
able to combine it with the address giv to get an
auto-inc address.) */
if (v->combined_with)
{
struct induction *other_giv = 0;
/* Find all BIVs in loop. */
loop_bivs_find (loop);
for (tv = bl->giv; tv; tv = tv->next_iv)
if (tv->same == v)
{
if (other_giv)
break;
else
other_giv = tv;
}
if (! tv && other_giv
&& REGNO (other_giv->dest_reg) < max_reg_before_loop
&& (REGNO_LAST_UID (REGNO (other_giv->dest_reg))
== INSN_UID (v->insn))
&& INSN_LUID (v->insn) < INSN_LUID (bl->biv->insn))
auto_inc_opt = 1;
}
/* Check for case where increment is before the address
giv. Do this test in "loop order". */
else if ((INSN_LUID (v->insn) > INSN_LUID (bl->biv->insn)
&& (INSN_LUID (v->insn) < INSN_LUID (loop->scan_start)
|| (INSN_LUID (bl->biv->insn)
> INSN_LUID (loop->scan_start))))
|| (INSN_LUID (v->insn) < INSN_LUID (loop->scan_start)
&& (INSN_LUID (loop->scan_start)
< INSN_LUID (bl->biv->insn))))
auto_inc_opt = -1;
else
auto_inc_opt = 1;
/* Exit if there are no bivs. */
if (! ivs->loop_iv_list)
#ifdef HAVE_cc0
{
/* Can still unroll the loop anyways, but indicate that there is no
strength reduction info available. */
if (flags & LOOP_UNROLL)
unroll_loop (loop, insn_count, end_insert_before, 0);
rtx prev;
goto egress;
/* We can't put an insn immediately after one setting
cc0, or immediately before one using cc0. */
if ((auto_inc_opt == 1 && sets_cc0_p (PATTERN (v->insn)))
|| (auto_inc_opt == -1
&& (prev = prev_nonnote_insn (v->insn)) != 0
&& INSN_P (prev)
&& sets_cc0_p (PATTERN (prev))))
auto_inc_opt = 0;
}
#endif
/* Determine how BIVS are initialised by looking through pre-header
extended basic block. */
loop_bivs_init_find (loop);
if (auto_inc_opt)
v->auto_inc_opt = 1;
}
#endif
/* Look at the each biv and see if we can say anything better about its
initial value from any initializing insns set up above. */
loop_bivs_check (loop);
/* For each place where the biv is incremented, add an insn
to increment the new, reduced reg for the giv. */
for (tv = bl->biv; tv; tv = tv->next_iv)
{
rtx insert_before;
/* Search the loop for general induction variables. */
loop_givs_find (loop);
if (! auto_inc_opt)
insert_before = tv->insn;
else if (auto_inc_opt == 1)
insert_before = NEXT_INSN (v->insn);
else
insert_before = v->insn;
/* Try to calculate and save the number of loop iterations. This is
set to zero if the actual number can not be calculated. This must
be called after all giv's have been identified, since otherwise it may
fail if the iteration variable is a giv. */
loop_iterations (loop);
if (tv->mult_val == const1_rtx)
emit_iv_add_mult (tv->add_val, v->mult_val,
v->new_reg, v->new_reg, insert_before);
else /* tv->mult_val == const0_rtx */
/* A multiply is acceptable here
since this is presumed to be seldom executed. */
emit_iv_add_mult (tv->add_val, v->mult_val,
v->add_val, v->new_reg, insert_before);
}
/* Now for each giv for which we still don't know whether or not it is
replaceable, check to see if it is replaceable because its final value
can be calculated. This must be done after loop_iterations is called,
so that final_giv_value will work correctly. */
loop_givs_check (loop);
/* Add code at loop start to initialize giv's reduced reg. */
/* Try to prove that the loop counter variable (if any) is always
nonnegative; if so, record that fact with a REG_NONNEG note
so that "decrement and branch until zero" insn can be used. */
check_dbra_loop (loop, insn_count);
emit_iv_add_mult (extend_value_for_giv (v, bl->initial_value),
v->mult_val, v->add_val, v->new_reg,
loop->start);
}
}
}
/* Create reg_map to hold substitutions for replaceable giv regs.
Some givs might have been made from biv increments, so look at
ivs->reg_iv_type for a suitable size. */
reg_map_size = ivs->reg_iv_type->num_elements;
reg_map = (rtx *) xcalloc (reg_map_size, sizeof (rtx));
/* Examine each iv class for feasibility of strength reduction/induction
variable elimination. */
/* Check for givs whose first use is their definition and whose
last use is the definition of another giv. If so, it is likely
dead and should not be used to derive another giv nor to
eliminate a biv. */
for (bl = ivs->loop_iv_list; bl; bl = bl->next)
{
static void
loop_givs_dead_check (loop, bl)
struct loop *loop ATTRIBUTE_UNUSED;
struct iv_class *bl;
{
struct induction *v;
int benefit;
int all_reduced;
rtx final_value = 0;
/* Test whether it will be possible to eliminate this biv
provided all givs are reduced. */
if (!(bl->eliminable = loop_biv_eliminable_p (loop, bl,
threshold, insn_count)))
{
if (loop_dump_stream)
for (v = bl->giv; v; v = v->next_iv)
{
fprintf (loop_dump_stream,
"Cannot eliminate biv %d.\n",
bl->regno);
fprintf (loop_dump_stream,
"First use: insn %d, last use: insn %d.\n",
REGNO_FIRST_UID (bl->regno),
REGNO_LAST_UID (bl->regno));
}
}
/* Check each extension dependent giv in this class to see if its
root biv is safe from wrapping in the interior mode. */
check_ext_dependant_givs (bl, loop_info);
/* Combine all giv's for this iv_class. */
combine_givs (regs, bl);
/* This will be true at the end, if all givs which depend on this
biv have been strength reduced.
We can't (currently) eliminate the biv unless this is so. */
all_reduced = 1;
/* Check each giv in this class to see if we will benefit by reducing
it. Skip giv's combined with others. */
for (v = bl->giv; v; v = v->next_iv)
{
struct induction *tv;
int add_cost;
if (v->ignore || v->same)
continue;
benefit = v->benefit;
PUT_MODE (test_reg, v->mode);
add_cost = iv_add_mult_cost (bl->biv->add_val, v->mult_val,
test_reg, test_reg);
/* Reduce benefit if not replaceable, since we will insert
a move-insn to replace the insn that calculates this giv.
Don't do this unless the giv is a user variable, since it
will often be marked non-replaceable because of the duplication
of the exit code outside the loop. In such a case, the copies
we insert are dead and will be deleted. So they don't have
a cost. Similar situations exist. */
/* ??? The new final_[bg]iv_value code does a much better job
of finding replaceable giv's, and hence this code may no longer
be necessary. */
if (! v->replaceable && ! bl->eliminable
&& REG_USERVAR_P (v->dest_reg))
benefit -= copy_cost;
/* Decrease the benefit to count the add-insns that we will
insert to increment the reduced reg for the giv.
??? This can overestimate the run-time cost of the additional
insns, e.g. if there are multiple basic blocks that increment
the biv, but only one of these blocks is executed during each
iteration. There is no good way to detect cases like this with
the current structure of the loop optimizer.
This code is more accurate for determining code size than
run-time benefits. */
benefit -= add_cost * bl->biv_count;
/* Decide whether to strength-reduce this giv or to leave the code
unchanged (recompute it from the biv each time it is used).
This decision can be made independently for each giv. */
#ifdef AUTO_INC_DEC
/* Attempt to guess whether autoincrement will handle some of the
new add insns; if so, increase BENEFIT (undo the subtraction of
add_cost that was done above). */
if (v->giv_type == DEST_ADDR
/* Increasing the benefit is risky, since this is only a guess.
Avoid increasing register pressure in cases where there would
be no other benefit from reducing this giv. */
&& benefit > 0
&& GET_CODE (v->mult_val) == CONST_INT)
{
if (HAVE_POST_INCREMENT
&& INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_PRE_INCREMENT
&& INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_POST_DECREMENT
&& -INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_PRE_DECREMENT
&& -INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
}
#endif
/* If an insn is not to be strength reduced, then set its ignore
flag, and clear all_reduced. */
/* A giv that depends on a reversed biv must be reduced if it is
used after the loop exit, otherwise, it would have the wrong
value after the loop exit. To make it simple, just reduce all
of such giv's whether or not we know they are used after the loop
exit. */
if (! flag_reduce_all_givs
&& v->lifetime * threshold * benefit < insn_count
&& ! bl->reversed)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"giv of insn %d not worth while, %d vs %d.\n",
INSN_UID (v->insn),
v->lifetime * threshold * benefit, insn_count);
v->ignore = 1;
all_reduced = 0;
}
else
{
/* Check that we can increment the reduced giv without a
multiply insn. If not, reject it. */
for (tv = bl->biv; tv; tv = tv->next_iv)
if (tv->mult_val == const1_rtx
&& ! product_cheap_p (tv->add_val, v->mult_val))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"giv of insn %d: would need a multiply.\n",
INSN_UID (v->insn));
v->ignore = 1;
all_reduced = 0;
break;
}
}
}
/* Check for givs whose first use is their definition and whose
last use is the definition of another giv. If so, it is likely
dead and should not be used to derive another giv nor to
eliminate a biv. */
for (v = bl->giv; v; v = v->next_iv)
{
if (v->ignore
|| (v->same && v->same->ignore))
continue;
if (v->ignore
|| (v->same && v->same->ignore))
continue;
if (v->giv_type == DEST_REG
&& REGNO_FIRST_UID (REGNO (v->dest_reg)) == INSN_UID (v->insn))
......@@ -4148,135 +4071,17 @@ strength_reduce (loop, insn_count, flags)
v->maybe_dead = 1;
}
}
}
/* Reduce each giv that we decided to reduce. */
for (v = bl->giv; v; v = v->next_iv)
{
struct induction *tv;
if (! v->ignore && v->same == 0)
{
int auto_inc_opt = 0;
/* If the code for derived givs immediately below has already
allocated a new_reg, we must keep it. */
if (! v->new_reg)
v->new_reg = gen_reg_rtx (v->mode);
#ifdef AUTO_INC_DEC
/* If the target has auto-increment addressing modes, and
this is an address giv, then try to put the increment
immediately after its use, so that flow can create an
auto-increment addressing mode. */
if (v->giv_type == DEST_ADDR && bl->biv_count == 1
&& bl->biv->always_executed && ! bl->biv->maybe_multiple
/* We don't handle reversed biv's because bl->biv->insn
does not have a valid INSN_LUID. */
&& ! bl->reversed
&& v->always_executed && ! v->maybe_multiple
&& INSN_UID (v->insn) < max_uid_for_loop)
{
/* If other giv's have been combined with this one, then
this will work only if all uses of the other giv's occur
before this giv's insn. This is difficult to check.
We simplify this by looking for the common case where
there is one DEST_REG giv, and this giv's insn is the
last use of the dest_reg of that DEST_REG giv. If the
increment occurs after the address giv, then we can
perform the optimization. (Otherwise, the increment
would have to go before other_giv, and we would not be
able to combine it with the address giv to get an
auto-inc address.) */
if (v->combined_with)
{
struct induction *other_giv = 0;
for (tv = bl->giv; tv; tv = tv->next_iv)
if (tv->same == v)
{
if (other_giv)
break;
else
other_giv = tv;
}
if (! tv && other_giv
&& REGNO (other_giv->dest_reg) < max_reg_before_loop
&& (REGNO_LAST_UID (REGNO (other_giv->dest_reg))
== INSN_UID (v->insn))
&& INSN_LUID (v->insn) < INSN_LUID (bl->biv->insn))
auto_inc_opt = 1;
}
/* Check for case where increment is before the address
giv. Do this test in "loop order". */
else if ((INSN_LUID (v->insn) > INSN_LUID (bl->biv->insn)
&& (INSN_LUID (v->insn) < INSN_LUID (loop->scan_start)
|| (INSN_LUID (bl->biv->insn)
> INSN_LUID (loop->scan_start))))
|| (INSN_LUID (v->insn) < INSN_LUID (loop->scan_start)
&& (INSN_LUID (loop->scan_start)
< INSN_LUID (bl->biv->insn))))
auto_inc_opt = -1;
else
auto_inc_opt = 1;
#ifdef HAVE_cc0
{
rtx prev;
/* We can't put an insn immediately after one setting
cc0, or immediately before one using cc0. */
if ((auto_inc_opt == 1 && sets_cc0_p (PATTERN (v->insn)))
|| (auto_inc_opt == -1
&& (prev = prev_nonnote_insn (v->insn)) != 0
&& INSN_P (prev)
&& sets_cc0_p (PATTERN (prev))))
auto_inc_opt = 0;
}
#endif
if (auto_inc_opt)
v->auto_inc_opt = 1;
}
#endif
/* For each place where the biv is incremented, add an insn
to increment the new, reduced reg for the giv. */
for (tv = bl->biv; tv; tv = tv->next_iv)
{
rtx insert_before;
if (! auto_inc_opt)
insert_before = tv->insn;
else if (auto_inc_opt == 1)
insert_before = NEXT_INSN (v->insn);
else
insert_before = v->insn;
if (tv->mult_val == const1_rtx)
emit_iv_add_mult (tv->add_val, v->mult_val,
v->new_reg, v->new_reg, insert_before);
else /* tv->mult_val == const0_rtx */
/* A multiply is acceptable here
since this is presumed to be seldom executed. */
emit_iv_add_mult (tv->add_val, v->mult_val,
v->add_val, v->new_reg, insert_before);
}
/* Add code at loop start to initialize giv's reduced reg. */
emit_iv_add_mult (extend_value_for_giv (v, bl->initial_value),
v->mult_val, v->add_val, v->new_reg,
loop_start);
}
}
/* Rescan all givs. If a giv is the same as a giv not reduced, mark it
as not reduced.
For each giv register that can be reduced now: if replaceable,
substitute reduced reg wherever the old giv occurs;
else add new move insn "giv_reg = reduced_reg". */
static void
loop_givs_rescan (loop, bl, reg_map, end_insert_before)
struct loop *loop;
struct iv_class *bl;
rtx *reg_map;
rtx end_insert_before;
{
struct induction *v;
for (v = bl->giv; v; v = v->next_iv)
{
......@@ -4338,24 +4143,6 @@ strength_reduce (loop, insn_count, flags)
else if (v->replaceable)
{
reg_map[REGNO (v->dest_reg)] = v->new_reg;
#if 0
/* I can no longer duplicate the original problem. Perhaps
this is unnecessary now? */
/* Replaceable; it isn't strictly necessary to delete the old
insn and emit a new one, because v->dest_reg is now dead.
However, especially when unrolling loops, the special
handling for (set REG0 REG1) in the second cse pass may
make v->dest_reg live again. To avoid this problem, emit
an insn to set the original giv reg from the reduced giv.
We can not delete the original insn, since it may be part
of a LIBCALL, and the code in flow that eliminates dead
libcalls will fail if it is deleted. */
emit_insn_after (gen_move_insn (v->dest_reg, v->new_reg),
v->insn);
#endif
}
else
{
......@@ -4383,25 +4170,11 @@ strength_reduce (loop, insn_count, flags)
how the loop exits. Otherwise, emit the insn after the loop,
since this is slightly more efficient. */
if (loop->exit_count)
insert_before = loop_start;
insert_before = loop->start;
else
insert_before = end_insert_before;
emit_insn_before (gen_move_insn (v->dest_reg, v->final_value),
insert_before);
#if 0
/* If the insn to set the final value of the giv was emitted
before the loop, then we must delete the insn inside the loop
that sets it. If this is a LIBCALL, then we must delete
every insn in the libcall. Note, however, that
final_giv_value will only succeed when there are multiple
exits if the giv is dead at each exit, hence it does not
matter that the original insn remains because it is dead
anyways. */
/* Delete the insn inside the loop that sets the giv since
the giv is now set before (or after) the loop. */
delete_insn (v->insn);
#endif
}
if (loop_dump_stream)
......@@ -4412,6 +4185,269 @@ strength_reduce (loop, insn_count, flags)
fprintf (loop_dump_stream, "\n");
}
}
}
static int
loop_giv_reduce_benefit (loop, bl, v, test_reg)
struct loop *loop ATTRIBUTE_UNUSED;
struct iv_class *bl;
struct induction *v;
rtx test_reg;
{
int add_cost;
int benefit;
benefit = v->benefit;
PUT_MODE (test_reg, v->mode);
add_cost = iv_add_mult_cost (bl->biv->add_val, v->mult_val,
test_reg, test_reg);
/* Reduce benefit if not replaceable, since we will insert a
move-insn to replace the insn that calculates this giv. Don't do
this unless the giv is a user variable, since it will often be
marked non-replaceable because of the duplication of the exit
code outside the loop. In such a case, the copies we insert are
dead and will be deleted. So they don't have a cost. Similar
situations exist. */
/* ??? The new final_[bg]iv_value code does a much better job of
finding replaceable giv's, and hence this code may no longer be
necessary. */
if (! v->replaceable && ! bl->eliminable
&& REG_USERVAR_P (v->dest_reg))
benefit -= copy_cost;
/* Decrease the benefit to count the add-insns that we will insert
to increment the reduced reg for the giv. ??? This can
overestimate the run-time cost of the additional insns, e.g. if
there are multiple basic blocks that increment the biv, but only
one of these blocks is executed during each iteration. There is
no good way to detect cases like this with the current structure
of the loop optimizer. This code is more accurate for
determining code size than run-time benefits. */
benefit -= add_cost * bl->biv_count;
/* Decide whether to strength-reduce this giv or to leave the code
unchanged (recompute it from the biv each time it is used). This
decision can be made independently for each giv. */
#ifdef AUTO_INC_DEC
/* Attempt to guess whether autoincrement will handle some of the
new add insns; if so, increase BENEFIT (undo the subtraction of
add_cost that was done above). */
if (v->giv_type == DEST_ADDR
/* Increasing the benefit is risky, since this is only a guess.
Avoid increasing register pressure in cases where there would
be no other benefit from reducing this giv. */
&& benefit > 0
&& GET_CODE (v->mult_val) == CONST_INT)
{
if (HAVE_POST_INCREMENT
&& INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_PRE_INCREMENT
&& INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_POST_DECREMENT
&& -INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
else if (HAVE_PRE_DECREMENT
&& -INTVAL (v->mult_val) == GET_MODE_SIZE (v->mem_mode))
benefit += add_cost * bl->biv_count;
}
#endif
return benefit;
}
/* Perform strength reduction and induction variable elimination.
Pseudo registers created during this function will be beyond the
last valid index in several tables including regs->n_times_set and
regno_last_uid. This does not cause a problem here, because the
added registers cannot be givs outside of their loop, and hence
will never be reconsidered. But scan_loop must check regnos to
make sure they are in bounds. */
static void
strength_reduce (loop, insn_count, flags)
struct loop *loop;
int insn_count;
int flags;
{
struct loop_info *loop_info = LOOP_INFO (loop);
struct loop_regs *regs = LOOP_REGS (loop);
struct loop_ivs *ivs = LOOP_IVS (loop);
rtx p;
/* Temporary list pointer for traversing ivs->loop_iv_list. */
struct iv_class *bl;
/* Ratio of extra register life span we can justify
for saving an instruction. More if loop doesn't call subroutines
since in that case saving an insn makes more difference
and more registers are available. */
/* ??? could set this to last value of threshold in move_movables */
int threshold = (loop_info->has_call ? 1 : 2) * (3 + n_non_fixed_regs);
/* Map of pseudo-register replacements. */
rtx *reg_map = NULL;
int reg_map_size;
rtx end_insert_before;
int unrolled_insn_copies = 0;
rtx test_reg = gen_rtx_REG (word_mode, LAST_VIRTUAL_REGISTER + 1);
addr_placeholder = gen_reg_rtx (Pmode);
/* Save insn immediately after the loop_end. Insns inserted after loop_end
must be put before this insn, so that they will appear in the right
order (i.e. loop order).
If loop_end is the end of the current function, then emit a
NOTE_INSN_DELETED after loop_end and set end_insert_before to the
dummy note insn. */
if (NEXT_INSN (loop->end) != 0)
end_insert_before = NEXT_INSN (loop->end);
else
end_insert_before = emit_note_after (NOTE_INSN_DELETED, loop->end);
/* Find all BIVs in loop. */
loop_bivs_find (loop);
/* Exit if there are no bivs. */
if (! ivs->loop_iv_list)
{
/* Can still unroll the loop anyways, but indicate that there is no
strength reduction info available. */
if (flags & LOOP_UNROLL)
unroll_loop (loop, insn_count, end_insert_before, 0);
goto egress;
}
/* Determine how BIVS are initialised by looking through pre-header
extended basic block. */
loop_bivs_init_find (loop);
/* Look at the each biv and see if we can say anything better about its
initial value from any initializing insns set up above. */
loop_bivs_check (loop);
/* Search the loop for general induction variables. */
loop_givs_find (loop);
/* Try to calculate and save the number of loop iterations. This is
set to zero if the actual number can not be calculated. This must
be called after all giv's have been identified, since otherwise it may
fail if the iteration variable is a giv. */
loop_iterations (loop);
/* Now for each giv for which we still don't know whether or not it is
replaceable, check to see if it is replaceable because its final value
can be calculated. This must be done after loop_iterations is called,
so that final_giv_value will work correctly. */
loop_givs_check (loop);
/* Try to prove that the loop counter variable (if any) is always
nonnegative; if so, record that fact with a REG_NONNEG note
so that "decrement and branch until zero" insn can be used. */
check_dbra_loop (loop, insn_count);
/* Create reg_map to hold substitutions for replaceable giv regs.
Some givs might have been made from biv increments, so look at
ivs->reg_iv_type for a suitable size. */
reg_map_size = ivs->reg_iv_type->num_elements;
reg_map = (rtx *) xcalloc (reg_map_size, sizeof (rtx));
/* Examine each iv class for feasibility of strength reduction/induction
variable elimination. */
for (bl = ivs->loop_iv_list; bl; bl = bl->next)
{
struct induction *v;
int benefit;
/* Test whether it will be possible to eliminate this biv
provided all givs are reduced. */
bl->eliminable = loop_biv_eliminable_p (loop, bl, threshold, insn_count);
/* Check each extension dependent giv in this class to see if its
root biv is safe from wrapping in the interior mode. */
check_ext_dependant_givs (bl, loop_info);
/* Combine all giv's for this iv_class. */
combine_givs (regs, bl);
/* This will be true at the end, if all givs which depend on this
biv have been strength reduced.
We can't (currently) eliminate the biv unless this is so. */
bl->all_reduced = 1;
for (v = bl->giv; v; v = v->next_iv)
{
struct induction *tv;
if (v->ignore || v->same)
continue;
benefit = loop_giv_reduce_benefit (loop, bl, v, test_reg);
/* If an insn is not to be strength reduced, then set its ignore
flag, and clear bl->all_reduced. */
/* A giv that depends on a reversed biv must be reduced if it is
used after the loop exit, otherwise, it would have the wrong
value after the loop exit. To make it simple, just reduce all
of such giv's whether or not we know they are used after the loop
exit. */
if (! flag_reduce_all_givs
&& v->lifetime * threshold * benefit < insn_count
&& ! bl->reversed)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"giv of insn %d not worth while, %d vs %d.\n",
INSN_UID (v->insn),
v->lifetime * threshold * benefit, insn_count);
v->ignore = 1;
bl->all_reduced = 0;
}
else
{
/* Check that we can increment the reduced giv without a
multiply insn. If not, reject it. */
for (tv = bl->biv; tv; tv = tv->next_iv)
if (tv->mult_val == const1_rtx
&& ! product_cheap_p (tv->add_val, v->mult_val))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"giv of insn %d: would need a multiply.\n",
INSN_UID (v->insn));
v->ignore = 1;
bl->all_reduced = 0;
break;
}
}
}
/* Check for givs whose first use is their definition and whose
last use is the definition of another giv. If so, it is likely
dead and should not be used to derive another giv nor to
eliminate a biv. */
loop_givs_dead_check (loop, bl);
/* Reduce each giv that we decided to reduce. */
loop_givs_reduce (loop, bl);
/* Rescan all givs. If a giv is the same as a giv not reduced, mark it
as not reduced.
For each giv register that can be reduced now: if replaceable,
substitute reduced reg wherever the old giv occurs;
else add new move insn "giv_reg = reduced_reg". */
loop_givs_rescan (loop, bl, reg_map, end_insert_before);
/* All the givs based on the biv bl have been reduced if they
merit it. */
......@@ -4421,23 +4457,23 @@ strength_reduce (loop, insn_count, flags)
v->new_reg will either be or refer to the register of the giv it
combined with.
Doing this clearing avoids problems in biv elimination where a
giv's new_reg is a complex value that can't be put in the insn but
the giv combined with (with a reg as new_reg) is marked maybe_dead.
Since the register will be used in either case, we'd prefer it be
used from the simpler giv. */
Doing this clearing avoids problems in biv elimination where
a giv's new_reg is a complex value that can't be put in the
insn but the giv combined with (with a reg as new_reg) is
marked maybe_dead. Since the register will be used in either
case, we'd prefer it be used from the simpler giv. */
for (v = bl->giv; v; v = v->next_iv)
if (! v->maybe_dead && v->same)
v->same->maybe_dead = 0;
/* Try to eliminate the biv, if it is a candidate.
This won't work if ! all_reduced,
This won't work if ! bl->all_reduced,
since the givs we planned to use might not have been reduced.
We have to be careful that we didn't initially think we could eliminate
this biv because of a giv that we now think may be dead and shouldn't
be used as a biv replacement.
We have to be careful that we didn't initially think we could
eliminate this biv because of a giv that we now think may be
dead and shouldn't be used as a biv replacement.
Also, there is the possibility that we may have a giv that looks
like it can be used to eliminate a biv, but the resulting insn
......@@ -4449,7 +4485,7 @@ strength_reduce (loop, insn_count, flags)
of the occurrences of the biv with a giv, but no harm was done in
doing so in the rare cases where it can occur. */
if (all_reduced == 1 && bl->eliminable
if (bl->all_reduced == 1 && bl->eliminable
&& maybe_eliminate_biv (loop, bl, 1, threshold, insn_count))
{
/* ?? If we created a new test to bypass the loop entirely,
......@@ -4464,7 +4500,7 @@ strength_reduce (loop, insn_count, flags)
Reversed bivs already have an insn after the loop setting their
value, so we don't need another one. We can't calculate the
proper final value for such a biv here anyways. */
if (final_value != 0 && ! bl->reversed)
if (bl->final_value && ! bl->reversed)
{
rtx insert_before;
......@@ -4473,27 +4509,15 @@ strength_reduce (loop, insn_count, flags)
how the loop exits. Otherwise, emit the insn after the
loop, since this is slightly more efficient. */
if (loop->exit_count)
insert_before = loop_start;
insert_before = loop->start;
else
insert_before = end_insert_before;
emit_insn_before (gen_move_insn (bl->biv->dest_reg, final_value),
emit_insn_before (gen_move_insn (bl->biv->dest_reg,
bl->final_value),
end_insert_before);
}
#if 0
/* Delete all of the instructions inside the loop which set
the biv, as they are all dead. If is safe to delete them,
because an insn setting a biv will never be part of a libcall. */
/* However, deleting them will invalidate the regno_last_uid info,
so keeping them around is more convenient. Final_biv_value
will only succeed when there are multiple exits if the biv
is dead at each exit, hence it does not matter that the original
insn remains, because it is dead anyways. */
for (v = bl->biv; v; v = v->next_iv)
delete_insn (v->insn);
#endif
if (loop_dump_stream)
fprintf (loop_dump_stream, "Reg %d: biv eliminated\n",
bl->regno);
......@@ -4503,7 +4527,7 @@ strength_reduce (loop, insn_count, flags)
/* Go through all the instructions in the loop, making all the
register substitutions scheduled in REG_MAP. */
for (p = loop_start; p != loop_end; p = NEXT_INSN (p))
for (p = loop->start; p != loop->end; p = NEXT_INSN (p))
if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
|| GET_CODE (p) == CALL_INSN)
{
......@@ -4906,6 +4930,7 @@ record_biv (loop, v, insn, dest_reg, inc_val, mult_val, location,
/* Set initial value to the reg itself. */
bl->initial_value = dest_reg;
bl->final_value = 0;
/* We haven't seen the initializing insn yet */
bl->init_insn = 0;
bl->init_set = 0;
......
gcc/loop.h
......@@ -164,17 +164,22 @@ struct iv_class
check_dbra_loop. */
struct induction *giv; /* List of all insns that compute a giv
from this reg. */
int total_benefit; /* Sum of BENEFITs of all those givs */
rtx initial_value; /* Value of reg at loop start */
rtx initial_test; /* Test performed on BIV before loop */
struct iv_class *next; /* Links all class structures together */
int total_benefit; /* Sum of BENEFITs of all those givs. */
rtx initial_value; /* Value of reg at loop start. */
rtx initial_test; /* Test performed on BIV before loop. */
rtx final_value; /* Value of reg at loop end, if known. */
struct iv_class *next; /* Links all class structures together. */
rtx init_insn; /* insn which initializes biv, 0 if none. */
rtx init_set; /* SET of INIT_INSN, if any. */
unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
unsigned eliminable : 1; /* 1 if plausible candidate for elimination. */
unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for this. */
unsigned eliminable : 1; /* 1 if plausible candidate for
elimination. */
unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for
this. */
unsigned reversed : 1; /* 1 if we reversed the loop that this
biv controls. */
unsigned all_reduced : 1; /* 1 if all givs using this biv have
been reduced. */
};
typedef struct loop_mem_info
......@@ -333,6 +338,8 @@ struct loop_info
struct loop_regs regs;
/* The induction variable information in loop. */
struct loop_ivs ivs;
/* Non-zero if call is in pre_header extended basic block. */
int pre_header_has_call;
};
/* Definitions used by the basic induction variable discovery code. */
......
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