/* Transformations based on profile information for values.
- Copyright (C) 2003 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2004 Free Software Foundation, Inc.
This file is part of GCC.
#include "recog.h"
#include "optabs.h"
#include "regs.h"
+#include "ggc.h"
-/* In this file value profile based optimizations will be placed (none are
- here just now, but they are hopefully coming soon).
+static struct value_prof_hooks *value_prof_hooks;
+
+/* In this file value profile based optimizations are placed. Currently the
+ following optimizations are implemented (for more detailed descriptions
+ see comments at value_profile_transformations):
+
+ 1) Division/modulo specialization. Provided that we can determine that the
+ operands of the division have some special properties, we may use it to
+ produce more effective code.
+ 2) Speculative prefetching. If we are able to determine that the difference
+ between addresses accessed by a memory reference is usually constant, we
+ may add the prefetch instructions.
Every such optimization should add its requirements for profiled values to
insn_values_to_profile function. This function is called from branch_prob
-- the expression that is profiled
-- list of counters starting from the first one. */
-static void insn_divmod_values_to_profile (rtx, unsigned *,
- struct histogram_value **);
-static void insn_values_to_profile (rtx, unsigned *, struct histogram_value **);
+/* For speculative prefetching, the range in that we do not prefetch (because
+ we assume that it will be in cache anyway). The asymmetry between min and
+ max range is trying to reflect the fact that the sequential prefetching
+ of the data is commonly done directly by hardware. Nevertheless, these
+ values are just a guess and should of course be target-specific. */
+
+#ifndef NOPREFETCH_RANGE_MIN
+#define NOPREFETCH_RANGE_MIN (-16)
+#endif
+#ifndef NOPREFETCH_RANGE_MAX
+#define NOPREFETCH_RANGE_MAX 32
+#endif
+
+static void insn_divmod_values_to_profile (rtx, histogram_values *);
+#ifdef HAVE_prefetch
+static bool insn_prefetch_values_to_profile (rtx, histogram_values *);
+static int find_mem_reference_1 (rtx *, void *);
+static void find_mem_reference_2 (rtx, rtx, void *);
+static bool find_mem_reference (rtx, rtx *, int *);
+#endif
+
+static void insn_values_to_profile (rtx, histogram_values *);
static rtx gen_divmod_fixed_value (enum machine_mode, enum rtx_code, rtx, rtx,
- rtx, gcov_type);
-static rtx gen_mod_pow2 (enum machine_mode, enum rtx_code, rtx, rtx, rtx);
+ rtx, gcov_type, int);
+static rtx gen_mod_pow2 (enum machine_mode, enum rtx_code, rtx, rtx, rtx, int);
static rtx gen_mod_subtract (enum machine_mode, enum rtx_code, rtx, rtx, rtx,
- int);
+ int, int, int);
+#ifdef HAVE_prefetch
+static rtx gen_speculative_prefetch (rtx, gcov_type, int);
+#endif
static bool divmod_fixed_value_transform (rtx insn);
static bool mod_pow2_value_transform (rtx);
static bool mod_subtract_transform (rtx);
+#ifdef HAVE_prefetch
+static bool speculative_prefetching_transform (rtx);
+#endif
\f
-/* Release the list of VALUES of length N_VALUES for that we want to measure
- histograms. */
-void
-free_profiled_values (unsigned n_values ATTRIBUTE_UNUSED,
- struct histogram_value *values)
-{
- free (values);
-}
-
/* Find values inside INSN for that we want to measure histograms for
- division/modulo optimization. */
+ division/modulo optimization and stores them to VALUES. */
static void
-insn_divmod_values_to_profile (rtx insn, unsigned *n_values,
- struct histogram_value **values)
+insn_divmod_values_to_profile (rtx insn, histogram_values *values)
{
rtx set, set_src, op1, op2;
enum machine_mode mode;
+ histogram_value hist;
if (!INSN_P (insn))
return;
/* Check for a special case where the divisor is power of 2. */
if ((GET_CODE (set_src) == UMOD) && !CONSTANT_P (op2))
{
- *values = xrealloc (*values,
- (*n_values + 1)
- * sizeof (struct histogram_value));
- (*values)[*n_values].value = op2;
- (*values)[*n_values].seq = NULL_RTX;
- (*values)[*n_values].mode = mode;
- (*values)[*n_values].insn = insn;
- (*values)[*n_values].type = HIST_TYPE_POW2;
- (*values)[*n_values].hdata.pow2.may_be_other = 1;
- (*n_values)++;
+ hist = ggc_alloc (sizeof (*hist));
+ hist->value = op2;
+ hist->seq = NULL_RTX;
+ hist->mode = mode;
+ hist->insn = insn;
+ hist->type = HIST_TYPE_POW2;
+ hist->hdata.pow2.may_be_other = 1;
+ VEC_safe_push (histogram_value, *values, hist);
}
/* Check whether the divisor is not in fact a constant. */
if (!CONSTANT_P (op2))
{
- *values = xrealloc (*values,
- (*n_values + 1)
- * sizeof (struct histogram_value));
- (*values)[*n_values].value = op2;
- (*values)[*n_values].mode = mode;
- (*values)[*n_values].seq = NULL_RTX;
- (*values)[*n_values].insn = insn;
- (*values)[*n_values].type = HIST_TYPE_SINGLE_VALUE;
- (*n_values)++;
+ hist = ggc_alloc (sizeof (*hist));
+ hist->value = op2;
+ hist->mode = mode;
+ hist->seq = NULL_RTX;
+ hist->insn = insn;
+ hist->type = HIST_TYPE_SINGLE_VALUE;
+ VEC_safe_push (histogram_value, *values, hist);
}
- /* For mod, check whether it is not often a noop (or replacable by
+ /* For mod, check whether it is not often a noop (or replaceable by
a few subtractions). */
if (GET_CODE (set_src) == UMOD && !side_effects_p (op1))
{
rtx tmp;
- *values = xrealloc (*values,
- (*n_values + 1)
- * sizeof (struct histogram_value));
+ hist = ggc_alloc (sizeof (*hist));
start_sequence ();
tmp = simplify_gen_binary (DIV, mode, copy_rtx (op1), copy_rtx (op2));
- (*values)[*n_values].value = force_operand (tmp, NULL_RTX);
- (*values)[*n_values].seq = get_insns ();
+ hist->value = force_operand (tmp, NULL_RTX);
+ hist->seq = get_insns ();
end_sequence ();
- (*values)[*n_values].mode = mode;
- (*values)[*n_values].insn = insn;
- (*values)[*n_values].type = HIST_TYPE_INTERVAL;
- (*values)[*n_values].hdata.intvl.int_start = 0;
- (*values)[*n_values].hdata.intvl.steps = 2;
- (*values)[*n_values].hdata.intvl.may_be_less = 1;
- (*values)[*n_values].hdata.intvl.may_be_more = 1;
- (*n_values)++;
+ hist->mode = mode;
+ hist->insn = insn;
+ hist->type = HIST_TYPE_INTERVAL;
+ hist->hdata.intvl.int_start = 0;
+ hist->hdata.intvl.steps = 2;
+ hist->hdata.intvl.may_be_less = 1;
+ hist->hdata.intvl.may_be_more = 1;
+ VEC_safe_push (histogram_value, *values, hist);
}
return;
}
}
+#ifdef HAVE_prefetch
+
+/* Called from find_mem_reference through for_each_rtx, finds a memory
+ reference. I.e. if *EXPR is a MEM, the reference to this MEM is stored
+ to *RET and the traversing of the expression is interrupted by returning 1.
+ Otherwise 0 is returned. */
+
+static int
+find_mem_reference_1 (rtx *expr, void *ret)
+{
+ rtx *mem = ret;
+
+ if (GET_CODE (*expr) == MEM)
+ {
+ *mem = *expr;
+ return 1;
+ }
+ return 0;
+}
+
+/* Called form find_mem_reference through note_stores to find out whether
+ the memory reference MEM is a store. I.e. if EXPR == MEM, the variable
+ FMR2_WRITE is set to true. */
+
+static int fmr2_write;
+static void
+find_mem_reference_2 (rtx expr, rtx pat ATTRIBUTE_UNUSED, void *mem)
+{
+ if (expr == mem)
+ fmr2_write = true;
+}
+
+/* Find a memory reference inside INSN, return it in MEM. Set WRITE to true
+ if it is a write of the mem. Return false if no memory reference is found,
+ true otherwise. */
+
+static bool
+find_mem_reference (rtx insn, rtx *mem, int *write)
+{
+ *mem = NULL_RTX;
+ for_each_rtx (&PATTERN (insn), find_mem_reference_1, mem);
+
+ if (!*mem)
+ return false;
+
+ fmr2_write = false;
+ note_stores (PATTERN (insn), find_mem_reference_2, *mem);
+ *write = fmr2_write;
+ return true;
+}
+
+/* Find values inside INSN for that we want to measure histograms for
+ a speculative prefetching. Add them to the list VALUES.
+ Returns true if such we found any such value, false otherwise. */
+
+static bool
+insn_prefetch_values_to_profile (rtx insn, histogram_values *values)
+{
+ rtx mem, address;
+ int write;
+ histogram_value hist;
+
+ if (!INSN_P (insn))
+ return false;
+
+ if (!find_mem_reference (insn, &mem, &write))
+ return false;
+
+ address = XEXP (mem, 0);
+ if (side_effects_p (address))
+ return false;
+
+ if (CONSTANT_P (address))
+ return false;
+
+ hist = ggc_alloc (sizeof (*hist));
+ hist->value = address;
+ hist->mode = GET_MODE (address);
+ hist->seq = NULL_RTX;
+ hist->insn = insn;
+ hist->type = HIST_TYPE_CONST_DELTA;
+ VEC_safe_push (histogram_value, *values, hist);
+
+ return true;
+}
+#endif
/* Find values inside INSN for that we want to measure histograms and adds
them to list VALUES (increasing the record of its length in N_VALUES). */
static void
-insn_values_to_profile (rtx insn,
- unsigned *n_values,
- struct histogram_value **values)
+insn_values_to_profile (rtx insn, histogram_values *values)
{
if (flag_value_profile_transformations)
- insn_divmod_values_to_profile (insn, n_values, values);
+ insn_divmod_values_to_profile (insn, values);
+
+#ifdef HAVE_prefetch
+ if (flag_speculative_prefetching)
+ insn_prefetch_values_to_profile (insn, values);
+#endif
}
/* Find list of values for that we want to measure histograms. */
-void
-find_values_to_profile (unsigned *n_values, struct histogram_value **values)
+static void
+rtl_find_values_to_profile (histogram_values *values)
{
rtx insn;
unsigned i;
- *n_values = 0;
- *values = NULL;
+ life_analysis (NULL, PROP_DEATH_NOTES);
+
+ *values = VEC_alloc (histogram_value, 0);
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
- insn_values_to_profile (insn, n_values, values);
+ insn_values_to_profile (insn, values);
- for (i = 0; i < *n_values; i++)
+ for (i = 0; i < VEC_length (histogram_value, *values); i++)
{
- switch ((*values)[i].type)
+ histogram_value hist = VEC_index (histogram_value, *values, i);
+
+ switch (hist->type)
{
case HIST_TYPE_INTERVAL:
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
+ if (dump_file)
+ fprintf (dump_file,
"Interval counter for insn %d, range %d -- %d.\n",
- INSN_UID ((*values)[i].insn),
- (*values)[i].hdata.intvl.int_start,
- ((*values)[i].hdata.intvl.int_start
- + (*values)[i].hdata.intvl.steps - 1));
- (*values)[i].n_counters = (*values)[i].hdata.intvl.steps +
- ((*values)[i].hdata.intvl.may_be_less ? 1 : 0) +
- ((*values)[i].hdata.intvl.may_be_more ? 1 : 0);
+ INSN_UID ((rtx)hist->insn),
+ hist->hdata.intvl.int_start,
+ (hist->hdata.intvl.int_start
+ + hist->hdata.intvl.steps - 1));
+ hist->n_counters = hist->hdata.intvl.steps +
+ (hist->hdata.intvl.may_be_less ? 1 : 0) +
+ (hist->hdata.intvl.may_be_more ? 1 : 0);
break;
case HIST_TYPE_POW2:
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
+ if (dump_file)
+ fprintf (dump_file,
"Pow2 counter for insn %d.\n",
- INSN_UID ((*values)[i].insn));
- (*values)[i].n_counters = GET_MODE_BITSIZE ((*values)[i].mode) +
- ((*values)[i].hdata.pow2.may_be_other ? 1 : 0);
+ INSN_UID ((rtx)hist->insn));
+ hist->n_counters
+ = GET_MODE_BITSIZE (hist->mode)
+ + (hist->hdata.pow2.may_be_other ? 1 : 0);
break;
case HIST_TYPE_SINGLE_VALUE:
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
+ if (dump_file)
+ fprintf (dump_file,
"Single value counter for insn %d.\n",
- INSN_UID ((*values)[i].insn));
- (*values)[i].n_counters = 3;
+ INSN_UID ((rtx)hist->insn));
+ hist->n_counters = 3;
break;
case HIST_TYPE_CONST_DELTA:
- if (rtl_dump_file)
- fprintf (rtl_dump_file,
+ if (dump_file)
+ fprintf (dump_file,
"Constant delta counter for insn %d.\n",
- INSN_UID ((*values)[i].insn));
- (*values)[i].n_counters = 4;
+ INSN_UID ((rtx)hist->insn));
+ hist->n_counters = 4;
break;
default:
abort ();
}
}
+ allocate_reg_info (max_reg_num (), FALSE, FALSE);
}
/* Main entry point. Finds REG_VALUE_PROFILE notes from profiler and uses
It would be possible to continue analogically for K * b for other small
K's, but it is probably not useful.
+ 5)
+
+ Read or write of mem[address], where the value of address changes usually
+ by a constant C != 0 between the following accesses to the computation; with
+ -fspeculative-prefetching we then add a prefetch of address + C before
+ the insn. This handles prefetching of several interesting cases in addition
+ to a simple prefetching for addresses that are induction variables, e. g.
+ linked lists allocated sequentially (even in case they are processed
+ recursively).
+
+ TODO -- we should also check whether there is not (usually) a small
+ difference with the adjacent memory references, so that we do
+ not issue overlapping prefetches. Also we should employ some
+ heuristics to eliminate cases where prefetching evidently spoils
+ the code.
+ -- it should somehow cooperate with the loop optimizer prefetching
+
TODO:
There are other useful cases that could be handled by a similar mechanism,
making unroller happy. Since this may grow the code significantly,
we would have to be very careful here. */
-bool
-value_profile_transformations (void)
+static bool
+rtl_value_profile_transformations (void)
{
rtx insn, next;
int changed = false;
if (!maybe_hot_bb_p (BLOCK_FOR_INSN (insn)))
continue;
- if (rtl_dump_file)
+ if (dump_file)
{
- fprintf (rtl_dump_file, "Trying transformations on insn %d\n",
+ fprintf (dump_file, "Trying transformations on insn %d\n",
INSN_UID (insn));
- print_rtl_single (rtl_dump_file, insn);
+ print_rtl_single (dump_file, insn);
}
/* Transformations: */
|| divmod_fixed_value_transform (insn)
|| mod_pow2_value_transform (insn)))
changed = true;
+#ifdef HAVE_prefetch
+ if (flag_speculative_prefetching
+ && speculative_prefetching_transform (insn))
+ changed = true;
+#endif
}
if (changed)
}
/* Generate code for transformation 1 (with MODE and OPERATION, operands OP1
- and OP2 whose value is expected to be VALUE and result TARGET). */
+ and OP2, whose value is expected to be VALUE, result TARGET and
+ probability of taking the optimal path PROB). */
static rtx
gen_divmod_fixed_value (enum machine_mode mode, enum rtx_code operation,
- rtx target, rtx op1, rtx op2, gcov_type value)
+ rtx target, rtx op1, rtx op2, gcov_type value,
+ int prob)
{
- rtx tmp, tmp1;
+ rtx tmp, tmp1, jump;
rtx neq_label = gen_label_rtx ();
rtx end_label = gen_label_rtx ();
rtx sequence;
do_compare_rtx_and_jump (tmp, GEN_INT (value), NE, 0, mode, NULL_RTX,
NULL_RTX, neq_label);
- tmp1 = simplify_gen_binary (operation, mode, copy_rtx (op1), GEN_INT (value));
+
+ /* Add branch probability to jump we just created. */
+ jump = get_last_insn ();
+ REG_NOTES (jump) = gen_rtx_EXPR_LIST (REG_BR_PROB,
+ GEN_INT (REG_BR_PROB_BASE - prob),
+ REG_NOTES (jump));
+
+ tmp1 = simplify_gen_binary (operation, mode,
+ copy_rtx (op1), GEN_INT (value));
tmp1 = force_operand (tmp1, target);
if (tmp1 != target)
emit_move_insn (copy_rtx (target), copy_rtx (tmp1));
emit_barrier ();
emit_label (neq_label);
- tmp1 = simplify_gen_binary (operation, mode, copy_rtx (op1), copy_rtx (tmp));
+ tmp1 = simplify_gen_binary (operation, mode,
+ copy_rtx (op1), copy_rtx (tmp));
tmp1 = force_operand (tmp1, target);
if (tmp1 != target)
emit_move_insn (copy_rtx (target), copy_rtx (tmp1));
enum machine_mode mode;
gcov_type val, count, all;
edge e;
+ int prob;
set = single_set (insn);
if (!set)
histogram = XEXP (histogram, 1);
all = INTVAL (XEXP (histogram, 0));
- /* We requiere that count is at least half of all; this means
+ /* We require that count is at least half of all; this means
that for the transformation to fire the value must be constant
- at least 50% of time (and 75% gives the garantee of usage). */
+ at least 50% of time (and 75% gives the guarantee of usage). */
if (!rtx_equal_p (op2, value) || 2 * count < all)
return false;
- if (rtl_dump_file)
- fprintf (rtl_dump_file, "Div/mod by constant transformation on insn %d\n",
+ if (dump_file)
+ fprintf (dump_file, "Div/mod by constant transformation on insn %d\n",
INSN_UID (insn));
+ /* Compute probability of taking the optimal path. */
+ prob = (count * REG_BR_PROB_BASE + all / 2) / all;
+
e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
delete_insn (insn);
insert_insn_on_edge (
- gen_divmod_fixed_value (mode, code, set_dest, op1, op2, val), e);
+ gen_divmod_fixed_value (mode, code, set_dest,
+ op1, op2, val, prob), e);
return true;
}
/* Generate code for transformation 2 (with MODE and OPERATION, operands OP1
- and OP2 and result TARGET). */
+ and OP2, result TARGET and probability of taking the optimal path PROB). */
static rtx
gen_mod_pow2 (enum machine_mode mode, enum rtx_code operation, rtx target,
- rtx op1, rtx op2)
+ rtx op1, rtx op2, int prob)
{
- rtx tmp, tmp1, tmp2, tmp3;
+ rtx tmp, tmp1, tmp2, tmp3, jump;
rtx neq_label = gen_label_rtx ();
rtx end_label = gen_label_rtx ();
rtx sequence;
0, OPTAB_WIDEN);
do_compare_rtx_and_jump (tmp2, const0_rtx, NE, 0, mode, NULL_RTX,
NULL_RTX, neq_label);
+
+ /* Add branch probability to jump we just created. */
+ jump = get_last_insn ();
+ REG_NOTES (jump) = gen_rtx_EXPR_LIST (REG_BR_PROB,
+ GEN_INT (REG_BR_PROB_BASE - prob),
+ REG_NOTES (jump));
+
tmp3 = expand_simple_binop (mode, AND, op1, tmp1, target,
0, OPTAB_WIDEN);
if (tmp3 != target)
enum machine_mode mode;
gcov_type wrong_values, count;
edge e;
- int i;
+ int i, all, prob;
set = single_set (insn);
if (!set)
if (count < wrong_values)
return false;
- if (rtl_dump_file)
- fprintf (rtl_dump_file, "Mod power of 2 transformation on insn %d\n",
+ if (dump_file)
+ fprintf (dump_file, "Mod power of 2 transformation on insn %d\n",
INSN_UID (insn));
+ /* Compute probability of taking the optimal path. */
+ all = count + wrong_values;
+ prob = (count * REG_BR_PROB_BASE + all / 2) / all;
+
e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
delete_insn (insn);
insert_insn_on_edge (
- gen_mod_pow2 (mode, code, set_dest, op1, op2), e);
+ gen_mod_pow2 (mode, code, set_dest, op1, op2, prob), e);
return true;
}
/* Generate code for transformations 3 and 4 (with MODE and OPERATION,
- operands OP1 and OP2, result TARGET and at most SUB subtractions). */
+ operands OP1 and OP2, result TARGET, at most SUB subtractions, and
+ probability of taking the optimal path(s) PROB1 and PROB2). */
static rtx
gen_mod_subtract (enum machine_mode mode, enum rtx_code operation,
- rtx target, rtx op1, rtx op2, int sub)
+ rtx target, rtx op1, rtx op2, int sub, int prob1, int prob2)
{
- rtx tmp, tmp1;
+ rtx tmp, tmp1, jump;
rtx end_label = gen_label_rtx ();
rtx sequence;
int i;
emit_move_insn (target, copy_rtx (op1));
do_compare_rtx_and_jump (target, tmp, LTU, 0, mode, NULL_RTX,
NULL_RTX, end_label);
-
+
+ /* Add branch probability to jump we just created. */
+ jump = get_last_insn ();
+ REG_NOTES (jump) = gen_rtx_EXPR_LIST (REG_BR_PROB,
+ GEN_INT (prob1), REG_NOTES (jump));
for (i = 0; i < sub; i++)
{
emit_move_insn (target, tmp1);
do_compare_rtx_and_jump (target, tmp, LTU, 0, mode, NULL_RTX,
NULL_RTX, end_label);
+
+ /* Add branch probability to jump we just created. */
+ jump = get_last_insn ();
+ REG_NOTES (jump) = gen_rtx_EXPR_LIST (REG_BR_PROB,
+ GEN_INT (prob2), REG_NOTES (jump));
}
tmp1 = simplify_gen_binary (operation, mode, copy_rtx (target), copy_rtx (tmp));
enum machine_mode mode;
gcov_type wrong_values, counts[2], count, all;
edge e;
- int i;
+ int i, prob1, prob2;
set = single_set (insn);
if (!set)
if (i == 2)
return false;
- if (rtl_dump_file)
- fprintf (rtl_dump_file, "Mod subtract transformation on insn %d\n",
+ if (dump_file)
+ fprintf (dump_file, "Mod subtract transformation on insn %d\n",
INSN_UID (insn));
+ /* Compute probability of taking the optimal path(s). */
+ prob1 = (counts[0] * REG_BR_PROB_BASE + all / 2) / all;
+ prob2 = (counts[1] * REG_BR_PROB_BASE + all / 2) / all;
+
e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
delete_insn (insn);
insert_insn_on_edge (
- gen_mod_subtract (mode, code, set_dest, op1, op2, i), e);
+ gen_mod_subtract (mode, code, set_dest,
+ op1, op2, i, prob1, prob2), e);
return true;
}
+
+#ifdef HAVE_prefetch
+/* Generate code for transformation 5 for mem with ADDRESS and a constant
+ step DELTA. WRITE is true if the reference is a store to mem. */
+
+static rtx
+gen_speculative_prefetch (rtx address, gcov_type delta, int write)
+{
+ rtx tmp;
+ rtx sequence;
+
+ /* TODO: we do the prefetching for just one iteration ahead, which
+ often is not enough. */
+ start_sequence ();
+ if (offsettable_address_p (0, VOIDmode, address))
+ tmp = plus_constant (copy_rtx (address), delta);
+ else
+ {
+ tmp = simplify_gen_binary (PLUS, Pmode,
+ copy_rtx (address), GEN_INT (delta));
+ tmp = force_operand (tmp, NULL);
+ }
+ if (! (*insn_data[(int)CODE_FOR_prefetch].operand[0].predicate)
+ (tmp, insn_data[(int)CODE_FOR_prefetch].operand[0].mode))
+ tmp = force_reg (Pmode, tmp);
+ emit_insn (gen_prefetch (tmp, GEN_INT (write), GEN_INT (3)));
+ sequence = get_insns ();
+ end_sequence ();
+
+ return sequence;
+}
+
+/* Do transform 5) on INSN if applicable. */
+
+static bool
+speculative_prefetching_transform (rtx insn)
+{
+ rtx histogram, value;
+ gcov_type val, count, all;
+ edge e;
+ rtx mem, address;
+ int write;
+
+ if (!maybe_hot_bb_p (BLOCK_FOR_INSN (insn)))
+ return false;
+
+ if (!find_mem_reference (insn, &mem, &write))
+ return false;
+
+ address = XEXP (mem, 0);
+ if (side_effects_p (address))
+ return false;
+
+ if (CONSTANT_P (address))
+ return false;
+
+ for (histogram = REG_NOTES (insn);
+ histogram;
+ histogram = XEXP (histogram, 1))
+ if (REG_NOTE_KIND (histogram) == REG_VALUE_PROFILE
+ && XEXP (XEXP (histogram, 0), 0) == GEN_INT (HIST_TYPE_CONST_DELTA))
+ break;
+
+ if (!histogram)
+ return false;
+
+ histogram = XEXP (XEXP (histogram, 0), 1);
+ value = XEXP (histogram, 0);
+ histogram = XEXP (histogram, 1);
+ /* Skip last value referenced. */
+ histogram = XEXP (histogram, 1);
+ val = INTVAL (XEXP (histogram, 0));
+ histogram = XEXP (histogram, 1);
+ count = INTVAL (XEXP (histogram, 0));
+ histogram = XEXP (histogram, 1);
+ all = INTVAL (XEXP (histogram, 0));
+
+ /* With that few executions we do not really have a reason to optimize the
+ statement, and more importantly, the data about differences of addresses
+ are spoiled by the first item that had no previous value to compare
+ with. */
+ if (all < 4)
+ return false;
+
+ /* We require that count is at least half of all; this means
+ that for the transformation to fire the value must be constant
+ at least 50% of time (and 75% gives the guarantee of usage). */
+ if (!rtx_equal_p (address, value) || 2 * count < all)
+ return false;
+
+ /* If the difference is too small, it does not make too much sense to
+ prefetch, as the memory is probably already in cache. */
+ if (val >= NOPREFETCH_RANGE_MIN && val <= NOPREFETCH_RANGE_MAX)
+ return false;
+
+ if (dump_file)
+ fprintf (dump_file, "Speculative prefetching for insn %d\n",
+ INSN_UID (insn));
+
+ e = split_block (BLOCK_FOR_INSN (insn), PREV_INSN (insn));
+
+ insert_insn_on_edge (gen_speculative_prefetch (address, val, write), e);
+
+ return true;
+}
+#endif /* HAVE_prefetch */
+\f
+/* Connection to the outside world. */
+/* Struct for IR-dependent hooks. */
+struct value_prof_hooks {
+ /* Find list of values for which we want to measure histograms. */
+ void (*find_values_to_profile) (histogram_values *);
+
+ /* Identify and exploit properties of values that are hard to analyze
+ statically. See value-prof.c for more detail. */
+ bool (*value_profile_transformations) (void);
+};
+
+/* Hooks for RTL-based versions (the only ones that currently work). */
+static struct value_prof_hooks rtl_value_prof_hooks =
+{
+ rtl_find_values_to_profile,
+ rtl_value_profile_transformations
+};
+
+void
+rtl_register_value_prof_hooks (void)
+{
+ value_prof_hooks = &rtl_value_prof_hooks;
+ if (ir_type ())
+ abort ();
+}
+\f
+/* Tree-based versions are stubs for now. */
+static void
+tree_find_values_to_profile (histogram_values *values ATTRIBUTE_UNUSED)
+{
+ abort ();
+}
+
+static bool
+tree_value_profile_transformations (void)
+{
+ abort ();
+}
+
+static struct value_prof_hooks tree_value_prof_hooks = {
+ tree_find_values_to_profile,
+ tree_value_profile_transformations
+};
+
+void
+tree_register_value_prof_hooks (void)
+{
+ value_prof_hooks = &tree_value_prof_hooks;
+ if (!ir_type ())
+ abort ();
+}
+\f
+/* IR-independent entry points. */
+void
+find_values_to_profile (histogram_values *values)
+{
+ (value_prof_hooks->find_values_to_profile) (values);
+}
+
+bool
+value_profile_transformations (void)
+{
+ return (value_prof_hooks->value_profile_transformations) ();
+}
+
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