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Add code to remove unused phis, converting to pruned SSA form, to avoid

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confusing the register allocator later.
This commit is contained in:
David Given 2016-10-12 21:50:12 +02:00
parent df239b3f90
commit 4723a1442f
3 changed files with 91 additions and 1 deletions
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1
mach/proto/mcg/mcg.h
View file

@ -112,6 +112,7 @@ extern void pass_live_vreg_analysis(void);
extern void pass_promote_float_ops(struct procedure* proc);
extern void pass_register_allocator(void);
extern void pass_remove_dead_blocks(struct procedure* proc);
extern void pass_remove_dead_phis(void);
extern void pass_split_critical_edges(struct procedure* proc);
extern FILE* outputfile;

88
mach/proto/mcg/pass_removedeadphis.c Normal file
View file

@ -0,0 +1,88 @@
#include "mcg.h"
static ARRAYOF(struct ir) phis;
static bool changed;
static void collect_phis(struct basicblock* bb)
{
int i;
for (i=0; i<bb->irs.count; i++)
{
struct ir* ir = bb->irs.item[i];
if (ir->opcode == IR_PHI)
array_append(&phis, ir);
}
}
static bool ir_walker_cb(struct ir* ir, void* user)
{
if (ir->left)
array_remove(&phis, ir->left);
if (ir->right)
array_remove(&phis, ir->right);
return false;
}
static void remove_referenced_phis(struct basicblock* bb)
{
int i, j;
for (i=0; i<bb->irs.count; i++)
{
struct ir* ir = bb->irs.item[i];
switch (ir->opcode)
{
case IR_PHI:
for (j=0; j<ir->u.phivalue.count; j++)
array_remove(&phis, ir->u.phivalue.item[j].right);
break;
default:
ir_walk(ir, ir_walker_cb, NULL);
break;
}
}
}
static void purge_unused_phis(struct basicblock* bb)
{
int i;
for (i=0; i<bb->irs.count; i++)
{
struct ir* ir = bb->irs.item[i];
if ((ir->opcode == IR_PHI) && (array_contains(&phis, ir)))
{
array_remove(&bb->irs, ir);
i--;
changed = true;
}
}
}
void pass_remove_dead_phis(void)
{
int i;
do
{
changed = false;
phis.count = 0;
for (i=0; i<cfg.preorder.count; i++)
collect_phis(cfg.preorder.item[i]);
for (i=0; i<cfg.preorder.count; i++)
remove_referenced_phis(cfg.preorder.item[i]);
for (i=0; i<cfg.preorder.count; i++)
purge_unused_phis(cfg.preorder.item[i]);
}
while (changed);
}
/* vim: set sw=4 ts=4 expandtab : */

3
mach/proto/mcg/procedure.c
View file

@ -159,9 +159,9 @@ void procedure_compile(struct procedure* proc)
{
int i;
pass_group_irs(proc);
print_blocks('1', proc);
pass_group_irs(proc);
/* Passes from here on must preserve IR grouping */
pass_eliminate_trivial_blocks(proc);
@ -180,6 +180,7 @@ void procedure_compile(struct procedure* proc)
print_blocks('4', proc);
pass_convert_locals_to_ssa(proc);
print_blocks('5', proc);
pass_remove_dead_phis();
pass_promote_float_ops(proc);
print_blocks('6', proc);