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expmed.c (alg_code): Add alg_unknown. 

* expmed.c (alg_code): Add alg_unknown.
	(alg_hash_entry): New.
	(NUM_ALG_HASH_ENTRIES): Likewise.
	(alg_hash): Likewise.
	(synth_mult): Cache the result into alg_hash.

From-SVN: r90825
This commit is contained in:
Kazu Hirata 2004-11-17 22:29:29 +00:00 committed by Kazu Hirata
parent 816ea94e17
commit 7b13ee6b32
2 changed files with 94 additions and 3 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2004-11-17 Kazu Hirata <kazu@cs.umass.edu>
* expmed.c (alg_code): Add alg_unknown.
(alg_hash_entry): New.
(NUM_ALG_HASH_ENTRIES): Likewise.
(alg_hash): Likewise.
(synth_mult): Cache the result into alg_hash.
2004-11-17 Zack Weinberg <zack@codesourcery.com>
* config/rs6000/t-darwin: Augment SHLIB_MAPFILES with

89
gcc/expmed.c
View File

@ -2297,7 +2297,7 @@ expand_shift (enum tree_code code, enum machine_mode mode, rtx shifted,
return temp;
}
enum alg_code { alg_zero, alg_m, alg_shift,
enum alg_code { alg_unknown, alg_zero, alg_m, alg_shift,
alg_add_t_m2, alg_sub_t_m2,
alg_add_factor, alg_sub_factor,
alg_add_t2_m, alg_sub_t2_m };
@ -2364,6 +2364,26 @@ struct algorithm
char log[MAX_BITS_PER_WORD];
};
/* The entry for our multiplication cache/hash table. */
struct alg_hash_entry {
/* The number we are multiplying by. */
unsigned int t;
/* The mode in which we are multiplying something by T. */
enum machine_mode mode;
/* The best multiplication algorithm for t. */
enum alg_code alg;
};
/* The number of cache/hash entries. */
#define NUM_ALG_HASH_ENTRIES 307
/* Each entry of ALG_HASH caches alg_code for some integer. This is
actually a hash table. If we have a collision, that the older
entry is kicked out. */
static struct alg_hash_entry alg_hash[NUM_ALG_HASH_ENTRIES];
/* Indicates the type of fixup needed after a constant multiplication.
BASIC_VARIANT means no fixup is needed, NEGATE_VARIANT means that
the result should be negated, and ADD_VARIANT means that the
@ -2400,6 +2420,9 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
int op_cost, op_latency;
unsigned HOST_WIDE_INT q;
int maxm = MIN (BITS_PER_WORD, GET_MODE_BITSIZE (mode));
int hash_index;
bool cache_hit = false;
enum alg_code cache_alg = alg_zero;
/* Indicate that no algorithm is yet found. If no algorithm
is found, this value will be returned and indicate failure. */
@ -2445,11 +2468,46 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
best_alg = alloca (sizeof (struct algorithm));
best_cost = *cost_limit;
/* Compute the hash index. */
hash_index = (t ^ (unsigned int) mode) % NUM_ALG_HASH_ENTRIES;
/* See if we already know what to do for T. */
if (alg_hash[hash_index].t == t
&& alg_hash[hash_index].mode == mode
&& alg_hash[hash_index].alg != alg_unknown)
{
cache_hit = true;
cache_alg = alg_hash[hash_index].alg;
switch (cache_alg)
{
case alg_shift:
goto do_alg_shift;
case alg_add_t_m2:
case alg_sub_t_m2:
goto do_alg_addsub_t_m2;
case alg_add_factor:
case alg_sub_factor:
goto do_alg_addsub_factor;
case alg_add_t2_m:
goto do_alg_add_t2_m;
case alg_sub_t2_m:
goto do_alg_sub_t2_m;
default:
gcc_unreachable ();
}
}
/* If we have a group of zero bits at the low-order part of T, try
multiplying by the remaining bits and then doing a shift. */
if ((t & 1) == 0)
{
do_alg_shift:
m = floor_log2 (t & -t); /* m = number of low zero bits */
if (m < maxm)
{
@ -2475,6 +2533,8 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
best_alg->op[best_alg->ops] = alg_shift;
}
}
if (cache_hit)
goto done;
}
/* If we have an odd number, add or subtract one. */
@ -2482,6 +2542,7 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
{
unsigned HOST_WIDE_INT w;
do_alg_addsub_t_m2:
for (w = 1; (w & t) != 0; w <<= 1)
;
/* If T was -1, then W will be zero after the loop. This is another
@ -2533,6 +2594,8 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
best_alg->op[best_alg->ops] = alg_add_t_m2;
}
}
if (cache_hit)
goto done;
}
/* Look for factors of t of the form
@ -2545,12 +2608,14 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
good sequence quickly, and therefore be able to prune (by decreasing
COST_LIMIT) the search. */
do_alg_addsub_factor:
for (m = floor_log2 (t - 1); m >= 2; m--)
{
unsigned HOST_WIDE_INT d;
d = ((unsigned HOST_WIDE_INT) 1 << m) + 1;
if (t % d == 0 && t > d && m < maxm)
if (t % d == 0 && t > d && m < maxm
&& (!cache_hit || cache_alg == alg_add_factor))
{
/* If the target has a cheap shift-and-add instruction use
that in preference to a shift insn followed by an add insn.
@ -2588,7 +2653,8 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
}
d = ((unsigned HOST_WIDE_INT) 1 << m) - 1;
if (t % d == 0 && t > d && m < maxm)
if (t % d == 0 && t > d && m < maxm
&& (!cache_hit || cache_alg == alg_sub_factor))
{
/* If the target has a cheap shift-and-subtract insn use
that in preference to a shift insn followed by a sub insn.
@ -2624,11 +2690,14 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
break;
}
}
if (cache_hit)
goto done;
/* Try shift-and-add (load effective address) instructions,
i.e. do a*3, a*5, a*9. */
if ((t & 1) != 0)
{
do_alg_add_t2_m:
q = t - 1;
q = q & -q;
m = exact_log2 (q);
@ -2650,7 +2719,10 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
best_alg->op[best_alg->ops] = alg_add_t2_m;
}
}
if (cache_hit)
goto done;
do_alg_sub_t2_m:
q = t + 1;
q = q & -q;
m = exact_log2 (q);
@ -2672,12 +2744,23 @@ synth_mult (struct algorithm *alg_out, unsigned HOST_WIDE_INT t,
best_alg->op[best_alg->ops] = alg_sub_t2_m;
}
}
if (cache_hit)
goto done;
}
done:
/* If best_cost has not decreased, we have not found any algorithm. */
if (!CHEAPER_MULT_COST (&best_cost, cost_limit))
return;
/* Cache the result. */
if (!cache_hit)
{
alg_hash[hash_index].t = t;
alg_hash[hash_index].mode = mode;
alg_hash[hash_index].alg = best_alg->op[best_alg->ops];
}
/* If we are getting a too long sequence for `struct algorithm'
to record, make this search fail. */
if (best_alg->ops == MAX_BITS_PER_WORD)