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simplify.c
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/*
* Simplify - do instruction simplification before CSE
*
* Copyright (C) 2004 Linus Torvalds
*/
#include <assert.h>
#include "parse.h"
#include "expression.h"
#include "linearize.h"
#include "flow.h"
#include "symbol.h"
/* Find the trivial parent for a phi-source */
static struct basic_block *phi_parent(struct basic_block *source, pseudo_t pseudo)
{
/* Can't go upwards if the pseudo is defined in the bb it came from.. */
if (pseudo->type == PSEUDO_REG) {
struct instruction *def = pseudo->def;
if (def->bb == source)
return source;
}
if (bb_list_size(source->children) != 1 || bb_list_size(source->parents) != 1)
return source;
return first_basic_block(source->parents);
}
/*
* Copy the phi-node's phisrcs into to given array.
* Returns 0 if the the list contained the expected
* number of element, a positive number if there was
* more than expected and a negative one if less.
*
* Note: we can't reuse a function like linearize_ptr_list()
* because any VOIDs in the phi-list must be ignored here
* as in this context they mean 'entry has been removed'.
*/
static int get_phisources(struct instruction *sources[], int nbr, struct instruction *insn)
{
pseudo_t phi;
int i = 0;
assert(insn->opcode == OP_PHI);
FOR_EACH_PTR(insn->phi_list, phi) {
struct instruction *def;
if (phi == VOID)
continue;
if (i >= nbr)
return 1;
def = phi->def;
assert(def->opcode == OP_PHISOURCE);
sources[i++] = def;
} END_FOR_EACH_PTR(phi);
return i - nbr;
}
static int if_convert_phi(struct instruction *insn)
{
struct instruction *array[2];
struct basic_block *parents[3];
struct basic_block *bb, *bb1, *bb2, *source;
struct instruction *br;
pseudo_t p1, p2;
bb = insn->bb;
if (get_phisources(array, 2, insn))
return 0;
if (linearize_ptr_list((struct ptr_list *)bb->parents, (void **)parents, 3) != 2)
return 0;
p1 = array[0]->src1;
bb1 = array[0]->bb;
p2 = array[1]->src1;
bb2 = array[1]->bb;
/* Only try the simple "direct parents" case */
if ((bb1 != parents[0] || bb2 != parents[1]) &&
(bb1 != parents[1] || bb2 != parents[0]))
return 0;
/*
* See if we can find a common source for this..
*/
source = phi_parent(bb1, p1);
if (source != phi_parent(bb2, p2))
return 0;
/*
* Cool. We now know that 'source' is the exclusive
* parent of both phi-nodes, so the exit at the
* end of it fully determines which one it is, and
* we can turn it into a select.
*
* HOWEVER, right now we only handle regular
* conditional branches. No multijumps or computed
* stuff. Verify that here.
*/
br = last_instruction(source->insns);
if (!br || br->opcode != OP_CBR)
return 0;
assert(br->cond);
assert(br->bb_false);
/*
* We're in business. Match up true/false with p1/p2.
*/
if (br->bb_true == bb2 || br->bb_false == bb1) {
pseudo_t p = p1;
p1 = p2;
p2 = p;
}
/*
* OK, we can now replace that last
*
* br cond, a, b
*
* with the sequence
*
* setcc cond
* select pseudo, p1, p2
* br cond, a, b
*
* and remove the phi-node. If it then
* turns out that 'a' or 'b' is entirely
* empty (common case), and now no longer
* a phi-source, we'll be able to simplify
* the conditional branch too.
*/
insert_select(source, br, insn, p1, p2);
kill_instruction(insn);
return REPEAT_CSE;
}
static int clean_up_phi(struct instruction *insn)
{
pseudo_t phi;
struct instruction *last;
int same;
last = NULL;
same = 1;
FOR_EACH_PTR(insn->phi_list, phi) {
struct instruction *def;
if (phi == VOID)
continue;
def = phi->def;
if (def->src1 == VOID || !def->bb)
continue;
if (last) {
if (last->src1 != def->src1)
same = 0;
continue;
}
last = def;
} END_FOR_EACH_PTR(phi);
if (same) {
pseudo_t pseudo = last ? last->src1 : VOID;
convert_instruction_target(insn, pseudo);
kill_instruction(insn);
return REPEAT_CSE;
}
return if_convert_phi(insn);
}
static int delete_pseudo_user_list_entry(struct pseudo_user_list **list, pseudo_t *entry, int count)
{
struct pseudo_user *pu;
FOR_EACH_PTR(*list, pu) {
if (pu->userp == entry) {
MARK_CURRENT_DELETED(pu);
if (!--count)
goto out;
}
} END_FOR_EACH_PTR(pu);
assert(count <= 0);
out:
if (ptr_list_size((struct ptr_list *) *list) == 0)
*list = NULL;
return count;
}
static inline void remove_usage(pseudo_t p, pseudo_t *usep)
{
if (has_use_list(p)) {
delete_pseudo_user_list_entry(&p->users, usep, 1);
if (!p->users)
kill_instruction(p->def);
}
}
void kill_use(pseudo_t *usep)
{
if (usep) {
pseudo_t p = *usep;
*usep = VOID;
remove_usage(p, usep);
}
}
static void kill_use_list(struct pseudo_list *list)
{
pseudo_t p;
FOR_EACH_PTR(list, p) {
if (p == VOID)
continue;
kill_use(THIS_ADDRESS(p));
} END_FOR_EACH_PTR(p);
}
/*
* kill an instruction:
* - remove it from its bb
* - remove the usage of all its operands
* If forse is zero, the normal case, the function only for
* instructions free of (possible) side-effects. Otherwise
* the function does that unconditionally (must only be used
* for unreachable instructions.
*/
void kill_insn(struct instruction *insn, int force)
{
if (!insn || !insn->bb)
return;
switch (insn->opcode) {
case OP_SEL:
case OP_RANGE:
kill_use(&insn->src3);
/* fall through */
case OP_BINARY ... OP_BINCMP_END:
kill_use(&insn->src2);
/* fall through */
case OP_CAST:
case OP_SCAST:
case OP_FPCAST:
case OP_PTRCAST:
case OP_SETVAL:
case OP_NOT: case OP_NEG:
case OP_SLICE:
kill_use(&insn->src1);
break;
case OP_PHI:
kill_use_list(insn->phi_list);
break;
case OP_PHISOURCE:
kill_use(&insn->phi_src);
break;
case OP_SYMADDR:
repeat_phase |= REPEAT_SYMBOL_CLEANUP;
break;
case OP_CBR:
case OP_COMPUTEDGOTO:
kill_use(&insn->cond);
break;
case OP_CALL:
if (!force) {
/* a "pure" function can be killed too */
if (!(insn->func->type == PSEUDO_SYM))
return;
if (!(insn->func->sym->ctype.modifiers & MOD_PURE))
return;
}
kill_use_list(insn->arguments);
if (insn->func->type == PSEUDO_REG)
kill_use(&insn->func);
break;
case OP_LOAD:
if (!force && insn->type->ctype.modifiers & MOD_VOLATILE)
return;
kill_use(&insn->src);
break;
case OP_STORE:
if (!force)
return;
kill_use(&insn->src);
kill_use(&insn->target);
break;
case OP_ENTRY:
/* ignore */
return;
case OP_BR:
default:
break;
}
insn->bb = NULL;
repeat_phase |= REPEAT_CSE;
return;
}
/*
* Kill trivially dead instructions
*/
static int dead_insn(struct instruction *insn, pseudo_t *src1, pseudo_t *src2, pseudo_t *src3)
{
struct pseudo_user *pu;
FOR_EACH_PTR(insn->target->users, pu) {
if (*pu->userp != VOID)
return 0;
} END_FOR_EACH_PTR(pu);
insn->bb = NULL;
kill_use(src1);
kill_use(src2);
kill_use(src3);
return REPEAT_CSE;
}
static inline int constant(pseudo_t pseudo)
{
return pseudo->type == PSEUDO_VAL;
}
static int replace_with_pseudo(struct instruction *insn, pseudo_t pseudo)
{
convert_instruction_target(insn, pseudo);
switch (insn->opcode) {
case OP_SEL:
case OP_RANGE:
kill_use(&insn->src3);
case OP_BINARY ... OP_BINCMP_END:
kill_use(&insn->src2);
case OP_NOT:
case OP_NEG:
case OP_SYMADDR:
case OP_CAST:
case OP_SCAST:
case OP_FPCAST:
case OP_PTRCAST:
kill_use(&insn->src1);
break;
default:
assert(0);
}
insn->bb = NULL;
return REPEAT_CSE;
}
static unsigned int value_size(long long value)
{
value >>= 8;
if (!value)
return 8;
value >>= 8;
if (!value)
return 16;
value >>= 16;
if (!value)
return 32;
return 64;
}
/*
* Try to determine the maximum size of bits in a pseudo.
*
* Right now this only follow casts and constant values, but we
* could look at things like logical 'and' instructions etc.
*/
static unsigned int operand_size(struct instruction *insn, pseudo_t pseudo)
{
unsigned int size = insn->size;
if (pseudo->type == PSEUDO_REG) {
struct instruction *src = pseudo->def;
if (src && src->opcode == OP_CAST && src->orig_type) {
unsigned int orig_size = src->orig_type->bit_size;
if (orig_size < size)
size = orig_size;
}
}
if (pseudo->type == PSEUDO_VAL) {
unsigned int orig_size = value_size(pseudo->value);
if (orig_size < size)
size = orig_size;
}
return size;
}
static int simplify_asr(struct instruction *insn, pseudo_t pseudo, long long value)
{
unsigned int size = operand_size(insn, pseudo);
if (value >= size) {
warning(insn->pos, "right shift by bigger than source value");
return replace_with_pseudo(insn, value_pseudo(0));
}
if (!value)
return replace_with_pseudo(insn, pseudo);
return 0;
}
static int simplify_mul_div(struct instruction *insn, long long value)
{
unsigned long long sbit = 1ULL << (insn->size - 1);
unsigned long long bits = sbit | (sbit - 1);
if (value == 1)
return replace_with_pseudo(insn, insn->src1);
switch (insn->opcode) {
case OP_MULS:
case OP_MULU:
if (value == 0)
return replace_with_pseudo(insn, insn->src2);
/* Fall through */
case OP_DIVS:
if (!(value & sbit)) // positive
break;
value |= ~bits;
if (value == -1) {
insn->opcode = OP_NEG;
return REPEAT_CSE;
}
}
return 0;
}
static int compare_opcode(int opcode, int inverse)
{
if (!inverse)
return opcode;
switch (opcode) {
case OP_SET_EQ: return OP_SET_NE;
case OP_SET_NE: return OP_SET_EQ;
case OP_SET_LT: return OP_SET_GE;
case OP_SET_LE: return OP_SET_GT;
case OP_SET_GT: return OP_SET_LE;
case OP_SET_GE: return OP_SET_LT;
case OP_SET_A: return OP_SET_BE;
case OP_SET_AE: return OP_SET_B;
case OP_SET_B: return OP_SET_AE;
case OP_SET_BE: return OP_SET_A;
default:
return opcode;
}
}
static int simplify_seteq_setne(struct instruction *insn, long long value)
{
pseudo_t old = insn->src1;
struct instruction *def = old->def;
pseudo_t src1, src2;
int inverse;
int opcode;
if (value != 0 && value != 1)
return 0;
if (!def)
return 0;
inverse = (insn->opcode == OP_SET_NE) == value;
opcode = def->opcode;
switch (opcode) {
case OP_BINCMP ... OP_BINCMP_END:
// Convert:
// setcc.n %t <- %a, %b
// setne.m %r <- %t, $0
// into:
// setcc.n %t <- %a, %b
// setcc.m %r <- %a, $b
// and similar for setne/eq ... 0/1
src1 = def->src1;
src2 = def->src2;
insn->opcode = compare_opcode(opcode, inverse);
use_pseudo(insn, src1, &insn->src1);
use_pseudo(insn, src2, &insn->src2);
remove_usage(old, &insn->src1);
return REPEAT_CSE;
default:
return 0;
}
}
static int simplify_constant_rightside(struct instruction *insn)
{
long long value = insn->src2->value;
switch (insn->opcode) {
case OP_OR_BOOL:
if (value == 1)
return replace_with_pseudo(insn, insn->src2);
goto case_neutral_zero;
case OP_SUB:
if (value) {
insn->opcode = OP_ADD;
insn->src2 = value_pseudo(-value);
return REPEAT_CSE;
}
/* Fall through */
case OP_ADD:
case OP_OR: case OP_XOR:
case OP_SHL:
case OP_LSR:
case_neutral_zero:
if (!value)
return replace_with_pseudo(insn, insn->src1);
return 0;
case OP_ASR:
return simplify_asr(insn, insn->src1, value);
case OP_MODU: case OP_MODS:
if (value == 1)
return replace_with_pseudo(insn, value_pseudo(0));
return 0;
case OP_DIVU: case OP_DIVS:
case OP_MULU: case OP_MULS:
return simplify_mul_div(insn, value);
case OP_AND_BOOL:
if (value == 1)
return replace_with_pseudo(insn, insn->src1);
/* Fall through */
case OP_AND:
if (!value)
return replace_with_pseudo(insn, insn->src2);
return 0;
case OP_SET_NE:
case OP_SET_EQ:
return simplify_seteq_setne(insn, value);
}
return 0;
}
static int simplify_constant_leftside(struct instruction *insn)
{
long long value = insn->src1->value;
switch (insn->opcode) {
case OP_ADD: case OP_OR: case OP_XOR:
if (!value)
return replace_with_pseudo(insn, insn->src2);
return 0;
case OP_SHL:
case OP_LSR: case OP_ASR:
case OP_AND:
case OP_MULU: case OP_MULS:
if (!value)
return replace_with_pseudo(insn, insn->src1);
return 0;
}
return 0;
}
static int simplify_constant_binop(struct instruction *insn)
{
/* FIXME! Verify signs and sizes!! */
long long left = insn->src1->value;
long long right = insn->src2->value;
unsigned long long ul, ur;
long long res, mask, bits;
mask = 1ULL << (insn->size-1);
bits = mask | (mask-1);
if (left & mask)
left |= ~bits;
if (right & mask)
right |= ~bits;
ul = left & bits;
ur = right & bits;
switch (insn->opcode) {
case OP_ADD:
res = left + right;
break;
case OP_SUB:
res = left - right;
break;
case OP_MULU:
res = ul * ur;
break;
case OP_MULS:
res = left * right;
break;
case OP_DIVU:
if (!ur)
return 0;
res = ul / ur;
break;
case OP_DIVS:
if (!right)
return 0;
if (left == mask && right == -1)
return 0;
res = left / right;
break;
case OP_MODU:
if (!ur)
return 0;
res = ul % ur;
break;
case OP_MODS:
if (!right)
return 0;
if (left == mask && right == -1)
return 0;
res = left % right;
break;
case OP_SHL:
res = left << right;
break;
case OP_LSR:
res = ul >> ur;
break;
case OP_ASR:
res = left >> right;
break;
/* Logical */
case OP_AND:
res = left & right;
break;
case OP_OR:
res = left | right;
break;
case OP_XOR:
res = left ^ right;
break;
case OP_AND_BOOL:
res = left && right;
break;
case OP_OR_BOOL:
res = left || right;
break;
/* Binary comparison */
case OP_SET_EQ:
res = left == right;
break;
case OP_SET_NE:
res = left != right;
break;
case OP_SET_LE:
res = left <= right;
break;
case OP_SET_GE:
res = left >= right;
break;
case OP_SET_LT:
res = left < right;
break;
case OP_SET_GT:
res = left > right;
break;
case OP_SET_B:
res = ul < ur;
break;
case OP_SET_A:
res = ul > ur;
break;
case OP_SET_BE:
res = ul <= ur;
break;
case OP_SET_AE:
res = ul >= ur;
break;
default:
return 0;
}
res &= bits;
replace_with_pseudo(insn, value_pseudo(res));
return REPEAT_CSE;
}
static int simplify_binop_same_args(struct instruction *insn, pseudo_t arg)
{
switch (insn->opcode) {
case OP_SET_NE:
case OP_SET_LT: case OP_SET_GT:
case OP_SET_B: case OP_SET_A:
if (Wtautological_compare)
warning(insn->pos, "self-comparison always evaluates to false");
case OP_SUB:
case OP_XOR:
return replace_with_pseudo(insn, value_pseudo(0));
case OP_SET_EQ:
case OP_SET_LE: case OP_SET_GE:
case OP_SET_BE: case OP_SET_AE:
if (Wtautological_compare)
warning(insn->pos, "self-comparison always evaluates to true");
return replace_with_pseudo(insn, value_pseudo(1));
case OP_AND:
case OP_OR:
return replace_with_pseudo(insn, arg);
case OP_AND_BOOL:
case OP_OR_BOOL:
remove_usage(arg, &insn->src2);
insn->src2 = value_pseudo(0);
insn->opcode = OP_SET_NE;
return REPEAT_CSE;
default:
break;
}
return 0;
}
static int simplify_binop(struct instruction *insn)
{
if (dead_insn(insn, &insn->src1, &insn->src2, NULL))
return REPEAT_CSE;
if (constant(insn->src1)) {
if (constant(insn->src2))
return simplify_constant_binop(insn);
return simplify_constant_leftside(insn);
}
if (constant(insn->src2))
return simplify_constant_rightside(insn);
if (insn->src1 == insn->src2)
return simplify_binop_same_args(insn, insn->src1);
return 0;
}
static void switch_pseudo(struct instruction *insn1, pseudo_t *pp1, struct instruction *insn2, pseudo_t *pp2)
{
pseudo_t p1 = *pp1, p2 = *pp2;
use_pseudo(insn1, p2, pp1);
use_pseudo(insn2, p1, pp2);
remove_usage(p1, pp1);
remove_usage(p2, pp2);
}
static int canonical_order(pseudo_t p1, pseudo_t p2)
{
/* symbol/constants on the right */
if (p1->type == PSEUDO_VAL)
return p2->type == PSEUDO_VAL;
if (p1->type == PSEUDO_SYM)
return p2->type == PSEUDO_SYM || p2->type == PSEUDO_VAL;
return 1;
}
static int simplify_commutative_binop(struct instruction *insn)
{
if (!canonical_order(insn->src1, insn->src2)) {
switch_pseudo(insn, &insn->src1, insn, &insn->src2);
return REPEAT_CSE;
}
return 0;
}
static inline int simple_pseudo(pseudo_t pseudo)
{
return pseudo->type == PSEUDO_VAL || pseudo->type == PSEUDO_SYM;
}
static int simplify_associative_binop(struct instruction *insn)
{
struct instruction *def;
pseudo_t pseudo = insn->src1;
if (!simple_pseudo(insn->src2))
return 0;
if (pseudo->type != PSEUDO_REG)
return 0;
def = pseudo->def;
if (def == insn)
return 0;
if (def->opcode != insn->opcode)
return 0;
if (!simple_pseudo(def->src2))
return 0;
if (ptr_list_size((struct ptr_list *)def->target->users) != 1)
return 0;
switch_pseudo(def, &def->src1, insn, &insn->src2);
return REPEAT_CSE;
}
static int simplify_constant_unop(struct instruction *insn)
{
long long val = insn->src1->value;
long long res, mask;
switch (insn->opcode) {
case OP_NOT:
res = ~val;
break;
case OP_NEG:
res = -val;
break;
default:
return 0;
}
mask = 1ULL << (insn->size-1);
res &= mask | (mask-1);
replace_with_pseudo(insn, value_pseudo(res));
return REPEAT_CSE;
}
static int simplify_unop(struct instruction *insn)
{
if (dead_insn(insn, &insn->src1, NULL, NULL))
return REPEAT_CSE;
if (constant(insn->src1))
return simplify_constant_unop(insn);
switch (insn->opcode) {
struct instruction *def;
case OP_NOT:
def = insn->src->def;
if (def && def->opcode == OP_NOT)
return replace_with_pseudo(insn, def->src);
break;
case OP_NEG:
def = insn->src->def;
if (def && def->opcode == OP_NEG)
return replace_with_pseudo(insn, def->src);
break;
default:
return 0;
}
return 0;
}
static int simplify_one_memop(struct instruction *insn, pseudo_t orig)
{
pseudo_t addr = insn->src;
pseudo_t new, off;
if (addr->type == PSEUDO_REG) {
struct instruction *def = addr->def;
if (def->opcode == OP_SYMADDR && def->src) {
kill_use(&insn->src);
use_pseudo(insn, def->src, &insn->src);
return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
}
if (def->opcode == OP_ADD) {
new = def->src1;
off = def->src2;
if (constant(off))
goto offset;
new = off;
off = def->src1;
if (constant(off))
goto offset;
return 0;
}
}
return 0;
offset:
/* Invalid code */
if (new == orig) {
if (new == VOID)
return 0;
/*
* If some BB have been removed it is possible that this
* memop is in fact part of a dead BB. In this case
* we must not warn since nothing is wrong.
* If not part of a dead BB this will be redone after
* the BBs have been cleaned up.
*/
if (repeat_phase & REPEAT_CFG_CLEANUP)
return 0;
new = VOID;
warning(insn->pos, "crazy programmer");
}
insn->offset += off->value;
use_pseudo(insn, new, &insn->src);
remove_usage(addr, &insn->src);
return REPEAT_CSE | REPEAT_SYMBOL_CLEANUP;
}
/*
* We walk the whole chain of adds/subs backwards. That's not
* only more efficient, but it allows us to find loops.
*/
static int simplify_memop(struct instruction *insn)
{
int one, ret = 0;
pseudo_t orig = insn->src;
do {
one = simplify_one_memop(insn, orig);
ret |= one;
} while (one);
return ret;
}
static long long get_cast_value(long long val, int old_size, int new_size, int sign)
{
long long mask;
if (sign && new_size > old_size) {
mask = 1 << (old_size-1);
if (val & mask)
val |= ~(mask | (mask-1));
}
mask = 1 << (new_size-1);
return val & (mask | (mask-1));
}
static int simplify_cast(struct instruction *insn)
{
struct symbol *orig_type;
int orig_size, size;
pseudo_t src;
if (dead_insn(insn, &insn->src, NULL, NULL))
return REPEAT_CSE;
orig_type = insn->orig_type;
if (!orig_type)
return 0;
/* Keep casts with pointer on either side (not only case of OP_PTRCAST) */
if (is_ptr_type(orig_type) || is_ptr_type(insn->type))
return 0;
orig_size = orig_type->bit_size;
size = insn->size;
src = insn->src;
/* A cast of a constant? */
if (constant(src)) {
int sign = orig_type->ctype.modifiers & MOD_SIGNED;
long long val = get_cast_value(src->value, orig_size, size, sign);
src = value_pseudo(val);
goto simplify;
}
/* A cast of a "and" might be a no-op.. */
if (src->type == PSEUDO_REG) {
struct instruction *def = src->def;
if (def->opcode == OP_AND && def->size >= size) {
pseudo_t val = def->src2;
if (val->type == PSEUDO_VAL) {
unsigned long long value = val->value;
if (!(value >> (size-1)))
goto simplify;
}
}
}
if (size == orig_size) {
int op = (orig_type->ctype.modifiers & MOD_SIGNED) ? OP_SCAST : OP_CAST;
if (insn->opcode == op)
goto simplify;
if (insn->opcode == OP_FPCAST && is_float_type(orig_type))
goto simplify;
}
return 0;
simplify:
return replace_with_pseudo(insn, src);
}
static int simplify_select(struct instruction *insn)
{
pseudo_t cond, src1, src2;
if (dead_insn(insn, &insn->src1, &insn->src2, &insn->src3))
return REPEAT_CSE;
cond = insn->src1;
src1 = insn->src2;
src2 = insn->src3;
if (constant(cond) || src1 == src2) {
pseudo_t *kill, take;
kill_use(&insn->src1);
take = cond->value ? src1 : src2;
kill = cond->value ? &insn->src3 : &insn->src2;