Commit dc46c1b3 authored by Moritz Kroll's avatar Moritz Kroll
Browse files

Implemented simple switch lowering

[r20872]
parent f2650920
......@@ -149,6 +149,15 @@ void lower_calls_with_compounds(const lower_params_t *params);
*/
void lower_CopyB(ir_graph *irg, unsigned max_size, unsigned native_mode_bytes);
/**
* Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
* They will either remain the same or be converted into if-cascades.
*
* @param irg The ir graph to be lowered.
* @param spare_size Allowed spare size for table switches in machine words.
* (Default in edgfe: 128)
*/
void lower_Switch(ir_graph *irg, unsigned spare_size);
/**
* A callback type for creating an intrinsic entity for a given opcode.
......
......@@ -198,6 +198,7 @@ libfirm_la_SOURCES = \
lower/lower_hl.c \
lower/lower_intrinsics.c \
lower/lower_mode_b.c \
lower/lower_switch.c \
net/firmnet.c \
obstack/obstack.c \
obstack/obstack_printf.c \
......
/*
* Copyright (C) 1995-2008 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 Lowering of Switches if necessary or advantageous.
* @author Moritz Kroll
* @version $Id$
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "ircons.h"
#include "irgwalk.h"
#include "irnode_t.h"
#include "irouts.h"
#define foreach_out_irn(irn, i, outirn) for(i = get_irn_n_outs(irn) - 1;\
i >= 0 && (outirn = get_irn_out(irn, i)); --i)
typedef struct walk_env {
unsigned spare_size; /**< the allowed spare size for table switches */
struct obstack obst; /**< the obstack where data is allocated on */
int changed; /**< indicates whether a change was performed */
} walk_env_t;
typedef struct case_data {
long value;
ir_node *target;
} case_data_t;
/**
* Add the new predecessor x to node node, which is either a Block or a Phi
*/
static void add_pred(ir_node* node, ir_node* x)
{
ir_node** ins;
int n;
int i;
assert(is_Block(node) || is_Phi(node));
n = get_irn_arity(node);
NEW_ARR_A(ir_node*, ins, n + 1);
for (i = 0; i < n; i++)
ins[i] = get_irn_n(node, i);
ins[n] = x;
set_irn_in(node, n + 1, ins);
}
/**
* Remove the predecessor x from node node one time, which is either a Block or a Phi
*/
static void remove_pred(ir_node* node, ir_node* x)
{
ir_node** ins;
int n;
int i, j;
assert(is_Block(node) || is_Phi(node));
n = get_irn_arity(node);
NEW_ARR_A(ir_node*, ins, n - 1);
for (i = 0, j = -1; i < n - 1; i++)
{
ins[++j] = get_irn_n(node, i);
if(ins[i] == x) j--;
}
assert(i == j + 1 && "x is not a pred of node");
set_irn_in(node, n - 1, ins);
}
/**
* Evaluate a switch and decide whether we should build a table switch.
*
* @param cond The Cond node representing the switch.
* @param spare_size Allowed spare size for table switches in machine words.
* (Default in edgfe: 128)
*/
static int should_do_table_switch(ir_node *cond, unsigned spare_size)
{
long default_pn;
int i;
ir_node *proj;
long switch_min = LONG_MAX, switch_max = LONG_MIN;
unsigned long spare, num_cases = 0;
/* TODO: Minimum size for jump table? */
if(get_irn_n_outs(cond) <= 4)
return;
default_pn = get_Cond_defaultProj(cond);
foreach_out_irn(cond, i, proj) {
long pn = get_Proj_proj(proj);
if(pn == default_pn)
continue;
if(pn < switch_min)
switch_min = pn;
if(pn > switch_max)
switch_max = pn;
num_cases++;
}
/*
* Here we have: num_cases and [switch_min, switch_max] interval.
* We do an if-cascade if there are too many spare numbers.
*/
spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
return spare < spare_size;
}
static int casecmp(const void *a, const void *b)
{
return ((case_data_t *) a)->value - ((case_data_t *) b)->value;
}
/**
* Creates an if cascade realizing binary search.
*/
static void create_if_cascade(ir_node *sel, ir_node *curblock, ir_node *defblock,
case_data_t *curcases, int numcases)
{
set_cur_block(curblock);
if(numcases == 1)
{
/* only one case: "if(sel == val) goto target else goto default;" */
ir_node *val = new_Const_long(get_irn_mode(sel), curcases[0].value);
ir_node *cmp = new_Cmp(sel, val);
ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
ir_node *cond = new_Cond(proj);
add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
add_pred(defblock, new_Proj(cond, mode_X, pn_Cond_false));
return;
} else if(numcases == 2) {
/* only two cases: "if(sel == val[0]) goto target[0];" */
ir_node *val = new_Const_long(get_irn_mode(sel), curcases[0].value);
ir_node *cmp = new_Cmp(sel, val);
ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
ir_node *cond = new_Cond(proj);
ir_node *in[1];
ir_node *neblock;
add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
in[0] = new_Proj(cond, mode_X, pn_Cond_false);
neblock = new_Block(1, in);
/* second part: "else if(sel == val[1]) goto target[1] else goto default;" */
val = new_Const_long(get_irn_mode(sel), curcases[1].value);
cmp = new_Cmp(sel, val);
proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
cond = new_Cond(proj);
add_pred(curcases[1].target, new_Proj(cond, mode_X, pn_Cond_true));
add_pred(defblock, new_Proj(cond, mode_X, pn_Cond_false));
return;
} else {
/* recursive case: split cases in the middle */
int midcase = numcases / 2;
ir_node *val = new_Const_long(get_irn_mode(sel), curcases[midcase].value);
ir_node *cmp = new_Cmp(sel, val);
ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
ir_node *cond = new_Cond(proj);
ir_node *in[1];
ir_node *ltblock;
ir_node *geblock;
in[0] = new_Proj(cond, mode_X, pn_Cond_true);
ltblock = new_Block(1, in);
set_cur_block(curblock);
in[0] = new_Proj(cond, mode_X, pn_Cond_false);
geblock = new_Block(1, in);
create_if_cascade(sel, ltblock, defblock, curcases, midcase);
create_if_cascade(sel, geblock, defblock, curcases + midcase, numcases - midcase);
}
}
/**
* Block-Walker: searches for Cond nodes with a non-boolean mode
*/
static void find_cond_nodes(ir_node *block, void *ctx)
{
walk_env_t *env = ctx;
ir_node *projx;
ir_node *cond;
ir_node *sel;
ir_mode *sel_mode;
long default_pn;
int i, j = 0, numcases;
ir_node *proj;
case_data_t *cases;
ir_node *condblock;
ir_node *defblock = NULL;
if(get_Block_n_cfgpreds(block) != 1)
return;
projx = get_Block_cfgpred(block, 0);
if(!is_Proj(projx))
return;
assert(get_irn_mode(projx) == mode_X);
cond = get_Proj_pred(projx);
if(!is_Cond(cond))
return;
sel = get_Cond_selector(cond);
sel_mode = get_irn_mode(sel);
if(sel_mode == mode_b) /* not a switch? */
return;
if(should_do_table_switch(cond, env->spare_size))
return;
/*
* Switch should be transformed into an if cascade.
* So first order the cases, so we can do a binary search on them.
*/
numcases = get_irn_n_outs(cond) - 1; // does not contain default case
cases = obstack_alloc(&env->obst, numcases * sizeof(*cases));
default_pn = get_Cond_defaultProj(cond);
foreach_out_irn(cond, i, proj) {
long pn = get_Proj_proj(proj);
if(pn == default_pn)
{
defblock = get_irn_out(proj, 0);
remove_pred(defblock, proj);
continue;
}
cases[j].value = pn;
cases[j].target = get_irn_out(proj, 0);
remove_pred(cases[j].target, proj);
j++;
}
assert(defblock != NULL && "Switch without default proj");
qsort(cases, numcases, sizeof(*cases), casecmp);
/* Now create the if cascade */
condblock = get_nodes_block(cond);
create_if_cascade(sel, condblock, defblock, cases, numcases);
obstack_free(&env->obst, cases);
}
/**
* Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
* They will either remain the same or be converted into if-cascades.
*
* @param irg The ir graph to be lowered.
* @param spare_size Allowed spare size for table switches in machine words.
* (Default in edgfe: 128)
*/
void lower_Switch(ir_graph *irg, unsigned spare_size)
{
walk_env_t env;
ir_graph *rem = current_ir_graph;
current_ir_graph = irg;
obstack_init(&env.obst);
env.spare_size = spare_size;
assure_irg_outs(irg);
irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
if(env.changed) {
/* control flow changed */
set_irg_outs_inconsistent(irg);
set_irg_doms_inconsistent(irg);
set_irg_extblk_inconsistent(irg);
set_irg_loopinfo_inconsistent(irg);
}
obstack_free(&env.obst, NULL);
current_ir_graph = rem;
}
......@@ -6458,6 +6458,10 @@
RelativePath="..\ir\lower\lower_mode_b.c"
>
</File>
<File
RelativePath="..\ir\lower\lower_switch.c"
>
</File>
</Filter>
<Filter
Name="net"
......
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