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/*
* Copyright (c) 2002-2010 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
* General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option)
* any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
# include "vvp_priv.h"
# include <assert.h>
/* Maximum vector bits in a thread. If a thread co-processor is
* implemented, this value may need to be reduced. At that time
* wider operations will need to be partitioned. For example
* shift operations on WIDE (say > 64k bit) registers.
*/
#define MAX_VEC (256*1024)
static struct allocation_score_s {
ivl_expr_t exp;
ivl_signal_t sig;
unsigned sig_word;
unsigned exp_bit : 24;
unsigned sig_bit : 24;
unsigned alloc : 8;
} allocation_map[MAX_VEC] = { {0} };
/* This is the largest bit to have lookaside values. */
static unsigned lookaside_top = 0;
static __inline__ ivl_expr_t peek_exp(unsigned addr)
{
return allocation_map[addr].exp;
}
static __inline__ unsigned peek_exp_bit(unsigned addr)
{
return allocation_map[addr].exp_bit;
}
static __inline__ void set_exp(unsigned addr, ivl_expr_t expr, unsigned ebit)
{
allocation_map[addr].exp = expr;
allocation_map[addr].exp_bit = ebit;
}
static __inline__ void set_sig(unsigned addr, ivl_signal_t expr,
unsigned sig_word, unsigned ebit)
{
allocation_map[addr].sig = expr;
allocation_map[addr].sig_word = sig_word;
allocation_map[addr].sig_bit = ebit;
}
/*
* This clears a vector that was previously allocated by
* allocate_vector. That is, it unmarks all the bits of the map that
* represent this vector.
*
* If the vector is based in one of 4 constant bit values, then there
* are no bits to clear. If the vector is based in the 4-8 result
* area, then someone is broken.
*/
void clr_vector(struct vector_info vec)
{
unsigned idx;
if (vec.base < 4)
return;
assert(vec.base >= 8);
for (idx = 0 ; idx < vec.wid ; idx += 1) {
assert( allocation_map[vec.base+idx].alloc > 0);
allocation_map[vec.base+idx].alloc -= 1;
}
}
static unsigned allocate_vector_no_lookaside(unsigned wid, int skip_lookaside)
{
unsigned base = 8;
unsigned idx = 0;
while (idx < wid) {
if (base+idx >= MAX_VEC)
return 0;
assert((base + idx) < MAX_VEC);
if ((allocation_map[base+idx].alloc > 0)
|| (skip_lookaside && peek_exp(base+idx))) {
base = base + idx + 1;
idx = 0;
} else {
idx += 1;
}
}
for (idx = 0 ; idx < wid ; idx += 1) {
allocation_map[base+idx].alloc += 1;
set_exp(base+idx, 0, 0);
set_sig(base+idx, 0, 0, 0);
}
return base;
}
/*
* This unconditionally allocates a stretch of bits from the register
* set. It never returns a bit addressed <8 (0-3 are constant, 4-7 are
* condition codes).
*
* First try to allocate a vector without interfering with any bits
* cached by the lookaside buffer. If that doesn't work, then try
* again without worrying about trashing lookaside results. This
* should lead to preferentially allocating new bits instead of
* constantly overwriting intermediate results.
*
* If there is no space for a vector of the given width, then give up
* and return 0.
*/
unsigned allocate_vector(unsigned wid)
{
unsigned base = allocate_vector_no_lookaside(wid, 1);
if (base == 0)
base = allocate_vector_no_lookaside(wid, 0);
return base;
}
/*
* This clears the expression cache of the allocation map. It is
* called to prevent reuse of existing expressions, normally at the
* start of a basic block, but also at the end of thread processing.
*/
void clear_expression_lookaside(void)
{
unsigned idx;
for (idx = 0 ; idx < lookaside_top ; idx += 1) {
set_exp(idx, 0, 0);
set_sig(idx, 0, 0, 0);
}
lookaside_top = 0;
}
static int test_expression_savable(ivl_expr_t expr)
{
switch (ivl_expr_type(expr)) {
case IVL_EX_NUMBER:
case IVL_EX_STRING:
return 1;
default:
return 0;
}
}
void save_expression_lookaside(unsigned addr, ivl_expr_t expr, unsigned wid)
{
unsigned idx;
assert(addr >= 8);
assert((addr+wid) <= MAX_VEC);
/* When saving an expression to the lookaside, also clear the
signal saved in the lookaside for these bits. The reason is
that an expression calculation will replace any signal
bits. */
for (idx = 0 ; idx < wid ; idx += 1)
set_sig(addr+idx, 0, 0, 0);
/* Only certain types of expressions are savable. */
if ( ! test_expression_savable(expr))
return;
for (idx = 0 ; idx < wid ; idx += 1) {
set_exp(addr+idx, expr, idx);
}
if ((addr+wid) > lookaside_top)
lookaside_top = addr+wid;
}
static void clear_signal_lookaside_bit(unsigned idx, ivl_signal_t sig, unsigned sig_word)
{
if (allocation_map[idx].alloc > 0)
return;
if (allocation_map[idx].sig != sig)
return;
if (allocation_map[idx].sig_word != sig_word)
return;
set_sig(idx, 0, 0, 0);
}
void save_signal_lookaside(unsigned addr, ivl_signal_t sig, unsigned sig_word, unsigned wid)
{
unsigned idx;
/* Don't bind any of the low bits to a signal. */
if (addr < 8 && wid > 0)
return;
assert((addr+wid) <= MAX_VEC);
for (idx = 8 ; idx < addr ; idx += 1)
clear_signal_lookaside_bit(idx, sig, sig_word);
for (idx = 0 ; idx < wid ; idx += 1)
set_sig(addr+idx, sig, sig_word, idx);
if ((addr+wid) > lookaside_top)
lookaside_top = addr+wid;
for (idx = addr+wid ; idx < lookaside_top ; idx += 1)
clear_signal_lookaside_bit(idx, sig, sig_word);
}
static int compare_exp(ivl_expr_t l, ivl_expr_t r)
{
if (! (l && r))
return 0;
if (l == r)
return 1;
if (ivl_expr_type(l) != ivl_expr_type(r))
return 0;
switch (ivl_expr_type(l)) {
case IVL_EX_NUMBER:
if (ivl_expr_width(l) != ivl_expr_width(r))
return 0;
{ const char*bitl = ivl_expr_bits(l);
const char*bitr = ivl_expr_bits(r);
unsigned idx;
for (idx = 0 ; idx < ivl_expr_width(l) ; idx += 1) {
if (bitl[idx] != bitr[idx])
return 0;
}
}
return 1;
case IVL_EX_SELECT:
if (! compare_exp(ivl_expr_oper1(l), ivl_expr_oper1(r)))
return 0;
if (ivl_expr_oper2(l) == 0 && ivl_expr_oper1(r) == 0)
return 1;
if (! compare_exp(ivl_expr_oper2(l), ivl_expr_oper2(r)))
return 0;
return 1;
case IVL_EX_SIGNAL:
if (ivl_expr_signal(l) != ivl_expr_signal(r))
return 0;
if (ivl_expr_width(l) != ivl_expr_width(r))
return 0;
/* Don't match array words. */
if (ivl_expr_oper1(l) || ivl_expr_oper1(r))
return 0;
return 1;
default:
break;
}
return 0;
}
static unsigned find_expression_lookaside(ivl_expr_t expr, unsigned wid)
{
unsigned idx, match;
ivl_signal_t sig;
if (lookaside_top <= wid)
return 0;
/* Look in the expression lookaside for this expression. */
assert(expr);
match = 0;
for (idx = 8 ; idx < lookaside_top ; idx += 1) {
if (! compare_exp(allocation_map[idx].exp, expr)) {
match = 0;
continue;
}
if (allocation_map[idx].exp_bit != match) {
match = 0;
continue;
}
match += 1;
if (match == wid)
return idx-match+1;
}
/* The general expression lookup failed. If this is an
IVL_EX_SIGNAL, then look again in the variable lookaside
(which is saved l-values) for the expression. */
if (ivl_expr_type(expr) != IVL_EX_SIGNAL)
return 0;
sig = ivl_expr_signal(expr);
/* Only reg signals (variables) will be in the signal
lookaside, because only blocking assigned values are in the
signal lookaside. */
if (ivl_signal_type(sig) != IVL_SIT_REG)
return 0;
/* Now look for signal value matches in the signal lookaside. */
match = 0;
for (idx = 8 ; idx < lookaside_top ; idx += 1) {
if (sig != allocation_map[idx].sig) {
match = 0;
continue;
}
if (allocation_map[idx].sig_bit != match) {
match = 0;
continue;
}
match += 1;
if (match == wid)
return idx-match+1;
}
return 0;
}
/*
* Look for the expression in the expression lookaside table. If it is
* there, then allocate it and return the base. In this case the
* caller will not need to evaluate the expression. If this function
* returns 0, then the expression is not found and nothing is allocated.
*/
unsigned allocate_vector_exp(ivl_expr_t expr, unsigned wid,
int exclusive_flag)
{
unsigned idx;
unsigned la = find_expression_lookaside(expr, wid);
if (la == 0)
return 0;
if (exclusive_flag) {
/* If the caller is requesting exclusive allocation of
the expression, then return not-found if a lookup
already matched the expression. */
for (idx = 0 ; idx < wid ; idx += 1)
if (allocation_map[la+idx].alloc)
return 0;
}
for (idx = 0 ; idx < wid ; idx += 1)
allocation_map[la+idx].alloc += 1;
return la;
}
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