Commit d56c188c authored by Christoph Mallon's avatar Christoph Mallon
Browse files

Add minimal fixpoint VRP.

[r27377]
parent dd69af4a
......@@ -1076,4 +1076,11 @@ void place_code(ir_graph *irg);
*/
ir_graph_pass_t *place_code_pass(const char *name);
/**
* Determine information about the values of nodes and perform simplications
* using this information. This optimization performs a data-flow analysis to
* find the minimal fixpoint.
*/
void fixpoint_vrp(ir_graph*);
#endif
/*
* Copyright (C) 1995-2010 University of Karlsruhe. All right reserved.
*
* This file is part of libFirm.
*
* This file may be distributed and/or modified under the terms of the
* GNU General Public License version 2 as published by the Free Software
* Foundation and appearing in the file LICENSE.GPL included in the
* packaging of this file.
*
* Licensees holding valid libFirm Professional Edition licenses may use
* this file in accordance with the libFirm Commercial License.
* Agreement provided with the Software.
*
* This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
* WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE.
*/
/**
* @file
* @brief Data-flow driven minimal fixpoint value range propagation
* @author Christoph Mallon
* @version $Id$
*/
#include "config.h"
#include "adt/pdeq.h"
#include "adt/obst.h"
#include "adt/xmalloc.h"
#include "debug.h"
#include "ircons.h"
#include "irdom.h"
#include "iredges.h"
#include "irgmod.h"
#include "irgraph.h"
#include "irgwalk.h"
#include "irnode.h"
#include "iroptimize.h"
#include "irtools.h"
#include "tv.h"
/* TODO:
* - Implement cleared/set bit calculation for Add, Sub, Minus, Mul, Div, Mod, Shl, Shr, Shrs, Rotl
* - Implement min/max calculation for And, Eor, Or, Not, Conv, Shl, Shr, Shrs, Rotl, Mux
* - Implement min/max calculation for Add, Sub, Minus, Mul, Div, Mod, Conv, Shl, Shr, Shrs, Rotl, Mux
*/
/* Tables of the cleared/set bit lattice
*
* Encoding of the lattice
* zo
* 00 0 zero
* 01 - impossible state, is zero /and/ one
* 10 T top, may be either zero or one
* 11 1 one
*
* S = Sum
* c = Carry
* D = Difference
* b = Borrow
*
* Not
* A ~
* 0 1
* 1 0
* T T
*
* Half adder, half subtractor, and, xor, or, Mux
* AB Sc Db & ^ | M
* 00 00 00 0 0 0 0
* 01 10 11 0 1 1 T
* 0T T0 TT 0 T T T
* 10 10 10 0 1 1 T
* 11 01 00 1 0 1 1
* 1T TT T0 T T 1 T
* T0 T0 T0 0 T T T
* T1 TT TT T T 1 T
* TT TT TT T T T T
*
* Full adder, full subtractor
* ABc-1 Sc Db
* 000 00 00
* 001 10 11
* 00T T0 TT
* 010 10 11
* 011 01 01
* 01T TT T1
* 0T0 T0 TT
* 0T1 TT T1
* 0TT TT TT
* 100 10 10
* 101 01 00
* 10T TT T0
* 110 01 00
* 111 11 11
* 11T T1 TT
* 1T0 TT T0
* 1T1 T1 TT
* 1TT TT TT
* T00 T0 T0
* T01 TT TT
* T0T TT TT
* T10 TT TT
* T11 T1 T1
* T1T TT TT
* TT0 TT TT
* TT1 TT TT
* TTT TT TT
*
*
* Assume: Xmin <= Xmax and no overflow
* A + B = (Amin + Bmin, Amax + Bmax)
* -A = (-Amax, -Amin)
* A - B = A + -B = (Amin (-B)min, Amax + (-B)max) = (Amin - Bmax, Amax - Bmin)
*/
DEBUG_ONLY(static firm_dbg_module_t *dbg;)
static struct obstack obst;
typedef struct bitinfo
{
tarval* z; // safe zeroes, 0 = bit is zero, 1 = bit maybe is 1
tarval* o; // safe ones, 0 = bit maybe is zero, 1 = bit is 1
} bitinfo;
static inline bitinfo* get_bitinfo(ir_node const* const irn)
{
return get_irn_link(irn);
}
static int set_bitinfo(ir_node* const irn, tarval* const z, tarval* const o)
{
bitinfo* b = get_bitinfo(irn);
if (b == NULL) {
b = OALLOCZ(&obst, bitinfo);
set_irn_link(irn, b);
} else if (z == b->z && o == b->o) {
return 0;
}
b->z = z;
b->o = o;
DB((dbg, LEVEL_3, "%+F: 0:%T 1:%T\n", irn, z, o));
return 1;
}
static int mode_is_intb(ir_mode const* const m)
{
return mode_is_int(m) || m == mode_b;
}
static int transfer(ir_node* const irn)
{
ir_mode* const m = get_irn_mode(irn);
tarval* z;
tarval* o;
if (m == mode_X) {
DB((dbg, LEVEL_3, "transfer %+F\n", irn));
switch (get_irn_opcode(irn)) {
case iro_Proj: {
ir_node* const pred = get_Proj_pred(irn);
if (is_Start(pred)) {
z = get_tarval_b_true();
o = get_tarval_b_false();
} else if (is_Cond(pred)) {
ir_node* const selector = get_Cond_selector(pred);
bitinfo* const b = get_bitinfo(selector);
tarval* const bz = b->z;
tarval* const bo = b->o;
if (get_irn_mode(selector) == mode_b) {
if (bz == bo) {
if ((bz == get_tarval_b_true()) == get_Proj_proj(irn)) {
z = o = get_tarval_b_true();
} else {
z = o = get_tarval_b_false();
}
} else {
goto result_unknown_X;
}
} else {
long const val = get_Proj_proj(irn);
if (val != get_Cond_default_proj(pred)) {
tarval* const tv = new_tarval_from_long(val, get_irn_mode(selector));
if (!tarval_is_null(tarval_andnot(tv, bz)) ||
!tarval_is_null(tarval_andnot(bo, tv))) {
// At least one bit differs.
z = o = get_tarval_b_false();
#if 0 // TODO must handle default Proj
} else if (bz == bo && bz == tv) {
z = o = get_tarval_b_true();
#endif
} else {
goto result_unknown_X;
}
} else {
goto cannot_analyse_X;
}
}
} else {
goto cannot_analyse_X;
}
break;
}
case iro_Jmp: {
bitinfo* const b = get_bitinfo(get_nodes_block(irn));
z = b->z;
o = b->o;
break;
}
default:
cannot_analyse_X:
DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
result_unknown_X:
z = get_tarval_b_true();
o = get_tarval_b_false();
break;
}
} else if (is_Block(irn)) {
int reachable = 0;
int const arity = get_Block_n_cfgpreds(irn);
int i;
DB((dbg, LEVEL_3, "transfer %+F\n", irn));
for (i = 0; i != arity; ++i) {
bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
if (b != NULL && b->z == get_tarval_b_true()) {
reachable = 1;
break;
}
}
o = get_tarval_b_false();
z = reachable || irn == get_irg_start_block(get_irn_irg(irn)) ? get_tarval_b_true() : o;
} else if (mode_is_intb(m)) {
DB((dbg, LEVEL_3, "transfer %+F\n", irn));
switch (get_irn_opcode(irn)) {
case iro_Const: {
z = o = get_Const_tarval(irn);
break;
}
case iro_Shl: {
bitinfo* const l = get_bitinfo(get_Shl_left(irn));
bitinfo* const r = get_bitinfo(get_Shl_right(irn));
tarval* const rz = r->z;
if (rz == r->o) {
z = tarval_shl(l->z, rz);
o = tarval_shl(l->o, rz);
} else {
goto cannot_analyse;
}
break;
}
case iro_Shr: {
bitinfo* const l = get_bitinfo(get_Shr_left(irn));
bitinfo* const r = get_bitinfo(get_Shr_right(irn));
tarval* const rz = r->z;
if (rz == r->o) {
z = tarval_shr(l->z, rz);
o = tarval_shr(l->o, rz);
} else {
goto cannot_analyse;
}
break;
}
case iro_Shrs: {
bitinfo* const l = get_bitinfo(get_Shrs_left(irn));
bitinfo* const r = get_bitinfo(get_Shrs_right(irn));
tarval* const rz = r->z;
if (rz == r->o) {
z = tarval_shrs(l->z, rz);
o = tarval_shrs(l->o, rz);
} else {
goto cannot_analyse;
}
break;
}
case iro_Rotl: {
bitinfo* const l = get_bitinfo(get_Rotl_left(irn));
bitinfo* const r = get_bitinfo(get_Rotl_right(irn));
tarval* const rz = r->z;
if (rz == r->o) {
z = tarval_rotl(l->z, rz);
o = tarval_rotl(l->o, rz);
} else {
goto cannot_analyse;
}
break;
}
case iro_Add: {
bitinfo* const l = get_bitinfo(get_Add_left(irn));
bitinfo* const r = get_bitinfo(get_Add_right(irn));
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
if (lz == lo && rz == ro) {
z = o = tarval_add(lz, rz);
} else {
// TODO improve: can only do lower disjoint bits
/* Determine where any of the operands has zero bits, i.e. where no
* carry out is generated if there is not carry in */
tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
/* Generate a mask of the lower consecutive zeroes: x | -x. In this
* range the addition is disjoint and therefore Add behaves like Or.
*/
tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
z = tarval_or( tarval_or(lz, rz), low_zero_mask);
tarval* const low_one_mask = tarval_not(low_zero_mask);
o = tarval_and(tarval_or(lo, ro), low_one_mask);
}
break;
}
case iro_Sub: {
bitinfo* const l = get_bitinfo(get_Sub_left(irn));
bitinfo* const r = get_bitinfo(get_Sub_right(irn));
if (l != NULL && r != NULL) { // Sub might subtract pointers.
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
if (lz == lo && rz == ro) {
z = o = tarval_sub(lz, rz, NULL);
} else if (tarval_is_null(tarval_andnot(rz, lo))) {
/* Every possible one of the subtrahend is backed by a safe one of the
* minuend, i.e. there are no borrows. */
// TODO extend no-borrow like carry for Add above
z = tarval_andnot(lz, ro);
o = tarval_andnot(lo, rz);
} else {
goto cannot_analyse;
}
} else {
goto cannot_analyse;
}
break;
}
case iro_Mul: {
bitinfo* const l = get_bitinfo(get_Mul_left(irn));
bitinfo* const r = get_bitinfo(get_Mul_right(irn));
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
if (lz == lo && rz == ro) {
z = o = tarval_mul(lz, rz);
} else {
// TODO improve
// Determine safe lower zeroes: x | -x.
tarval* const lzn = tarval_or(lz, tarval_neg(lz));
tarval* const rzn = tarval_or(rz, tarval_neg(rz));
// Concatenate safe lower zeroes.
if (tarval_cmp(lzn, rzn) == pn_Cmp_Lt) {
z = tarval_mul(tarval_eor(lzn, tarval_shl(lzn, get_tarval_one(m))), rzn);
} else {
z = tarval_mul(tarval_eor(rzn, tarval_shl(rzn, get_tarval_one(m))), lzn);
}
o = get_tarval_null(m);
}
break;
}
case iro_Minus: {
bitinfo* const b = get_bitinfo(get_Minus_op(irn));
if (b->z == b->o) {
z = o = tarval_neg(b->z);
} else {
goto cannot_analyse;
}
break;
}
case iro_And: {
bitinfo* const l = get_bitinfo(get_And_left(irn));
bitinfo* const r = get_bitinfo(get_And_right(irn));
z = tarval_and(l->z, r->z);
o = tarval_and(l->o, r->o);
break;
}
case iro_Or: {
bitinfo* const l = get_bitinfo(get_Or_left(irn));
bitinfo* const r = get_bitinfo(get_Or_right(irn));
z = tarval_or(l->z, r->z);
o = tarval_or(l->o, r->o);
break;
}
case iro_Eor: {
bitinfo* const l = get_bitinfo(get_Eor_left(irn));
bitinfo* const r = get_bitinfo(get_Eor_right(irn));
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
break;
}
case iro_Not: {
bitinfo* const b = get_bitinfo(get_Not_op(irn));
z = tarval_not(b->o);
o = tarval_not(b->z);
break;
}
case iro_Conv: {
bitinfo* const b = get_bitinfo(get_Conv_op(irn));
if (b == NULL) // Happens when converting from float values.
goto result_unknown;
z = tarval_convert_to(b->z, m);
o = tarval_convert_to(b->o, m);
break;
}
case iro_Mux: {
bitinfo* const f = get_bitinfo(get_Mux_false(irn));
bitinfo* const t = get_bitinfo(get_Mux_true(irn));
bitinfo* const c = get_bitinfo(get_Mux_sel(irn));
if (c->o == get_tarval_b_true()) {
z = t->z;
o = t->o;
} else if (c->z == get_tarval_b_false()) {
z = f->z;
o = f->o;
} else {
z = tarval_or( f->z, t->z);
z = tarval_and(f->o, t->o);
}
}
case iro_Phi: {
ir_node* const block = get_nodes_block(irn);
int const arity = get_Phi_n_preds(irn);
int i;
z = get_tarval_null(m);
o = get_tarval_all_one(m);
for (i = 0; i != arity; ++i) {
bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
if (b_cfg != NULL && b_cfg->z != get_tarval_b_false()) {
bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
z = tarval_or( z, b->z);
o = tarval_and(o, b->o);
}
}
break;
}
case iro_Proj: {
ir_node* const pred = get_Proj_pred(irn);
if (is_Cmp(pred)) { // TODO generalize
bitinfo* const l = get_bitinfo(get_Cmp_left(pred));
bitinfo* const r = get_bitinfo(get_Cmp_right(pred));
if (l == NULL || r == NULL)
goto result_unknown; // Cmp compares something we cannot evaluate.
switch (get_Proj_proj(irn)) {
case pn_Cmp_Lg: {
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
if (!tarval_is_null(tarval_andnot(ro, lz)) ||
!tarval_is_null(tarval_andnot(lo, rz))) {
// At least one bit differs.
z = o = get_tarval_b_true();
} else if (lz == lo && rz == ro && lz == rz) {
z = o = get_tarval_b_false();
} else {
goto result_unknown;
}
break;
}
case pn_Cmp_Eq: {
tarval* const lz = l->z;
tarval* const lo = l->o;
tarval* const rz = r->z;
tarval* const ro = r->o;
if (!tarval_is_null(tarval_andnot(ro, lz)) ||
!tarval_is_null(tarval_andnot(lo, rz))) {
// At least one bit differs.
z = o = get_tarval_b_false();
} else if (lz == lo && rz == ro && lz == rz) {
z = o = get_tarval_b_true();
} else {
goto result_unknown;
}
break;
}
default:
goto cannot_analyse;
}
} else {
goto cannot_analyse;
}
break;
}
default: {
cannot_analyse:
DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
result_unknown:
z = get_tarval_all_one(m);
o = get_tarval_null(m);
break;
}
}
} else {
return 0;
}
return set_bitinfo(irn, z, o);
}
static void first_round(ir_node* const irn, void* const env)
{
pdeq* const q = env;
transfer(irn);
if (is_Phi(irn) || is_Block(irn)) {
/* Only Phis (and their users) need another round, if we did not have
* information about all their inputs in the first round, i.e. in loops. */
/* TODO inserts all Phis, should only insert Phis, which did no have all
* predecessors available */
pdeq_putr(q, irn);
}
}
static void apply_result(ir_node* const irn, void* const env)
{
bitinfo* const b = get_bitinfo(irn);
tarval* z;
tarval* o;
(void)env;
if (!b) return;
if (is_Const(irn)) return; // It cannot get any better than a Const.
z = b->z;
o = b->o;
// Only display information if we could find out anything about the value.
DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
// Replace node with constant value by Const.
if (z == o) {
ir_mode* const m = get_irn_mode(irn);
ir_node* n;
if (mode_is_intb(m)) {
n = new_Const(z);
} else if (m == mode_X) {
ir_node* const block = get_nodes_block(irn);
ir_graph* const irg = get_Block_irg(block);
if (z == get_tarval_b_true()) {
// Might produce an endless loop, so keep the block.
add_End_keepalive(get_irg_end(irg), block);
n = new_r_Jmp(block);
} else {
n = new_r_Bad(irg);
/* Transferring analysis information to the bad node makes it a
* candidate for replacement. */
goto exchange_only;
}
} else {
return;
}
set_irn_link(n, b);
exchange_only:
exchange(irn, n);
}
switch (get_irn_opcode(irn)) {
case iro_And: {
ir_node* const l = get_And_left(irn);
ir_node* const r = get_And_right(irn);
bitinfo const* const bl = get_bitinfo(l);
bitinfo const* const br = get_bitinfo(r);
if (bl->z == bl->o) {
if (tarval_is_null(tarval_andnot(br->z, bl->z))) {
DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
exchange(irn, r);
}
} else if (br->z == br->o) {
if (tarval_is_null(tarval_andnot(bl->z, br->z))) {
DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
exchange(irn, l);
}
}
break;
}
case iro_Or: {
ir_node* const l = get_Or_left(irn);
ir_node* const r = get_Or_right(irn);
bitinfo const* const bl = get_bitinfo(l);
bitinfo const* const br = get_bitinfo(r);