/* 构造表达式的值,并将其添加到 t,src1,src2三个变量的uses 中 */
void DefineTemp (Symbol t, int op, Symbol src1, Symbol src2)
{
ValueDef def;
CALLOC(def);
def->dst = t;
def->op = op;
def->src1 = src1;
def->src2 = src2;
def->ownBB = CurrentBB;
/* 赋值和函数调用 */
if (op == MOV || op == CALL) {
/* 将值添加到变量t 中 */
def->link = AsVar(t)->def;
AsVar(t)->def = def;
return;
}
/* 如果src1 和src2是变量则将值添加进去 */
if (src1->kind == SK_Variable) {
TrackValueUse (src1, def);
}
if (src2 && src2->kind == SK_Variable) {
TrackValueUse (src2, def);
}
AsVar(t)->def = def;
}
static char* GetAccessName(Symbol p)
{
if (p->aname != NULL)
return p->aname;
switch (p->kind)
{
case SK_Constant:
p->aname = FormatName("$%s", p->name);
break;
case SK_String:
case SK_Label:
p->aname = FormatName(".%s", p->name);
break;
case SK_Variable:
case SK_Temp:
if (p->level == 0)
{
p->aname = p->name;
}
else if (p->sclass == TK_STATIC)
{
p->aname = FormatName("%s.%d", p->name, TempNum++);
}
else
{
p->aname = FormatName("%d(%%ebp)", AsVar(p)->offset);
}
break;
case SK_Function:
p->aname = p->name;
break;
case SK_Offset:
{
Symbol base = p->link;
int n = AsVar(p)->offset;
if (base->level == 0 || base->sclass == TK_STATIC)
{
p->aname = FormatName("%s%s%d", GetAccessName(base), n >= 0 ? "+" : "", n);
}
else
{
n += AsVar(base)->offset;
p->aname = FormatName("%d(%%ebp)", n);
}
}
break;
default:
assert(0);
}
return p->aname;
}
void DefineTemp(Symbol t, int op, Symbol src1, Symbol src2)
{
ValueDef def;
ALLOC(def);
def->dst = t;
def->op = op;
def->src1 = src1;
def->src2 = src2;
def->ownBB = CurrentBB;
if (op == MOV || op == CALL)
{
def->link = AsVar(t)->def;
AsVar(t)->def = def;
return;
}
if (src1->kind == SK_Variable)
{
TrackValueUse(src1, def);
}
if (src2 && src2->kind == SK_Variable)
{
TrackValueUse(src2, def);
}
AsVar(t)->def = def;
}
/* 将值def, 添加到符号p 中 */
static void TrackValueUse (Symbol p, ValueDef def)
{
ValueUse use;
CALLOC(use);
use->def = def;
use->next = AsVar(p)->uses;
AsVar(p)->uses = use;
}
Symbol Deref(Type ty, Symbol addr)
{
Symbol tmp;
if (addr->kind == SK_Temp && AsVar(addr)->def->op == ADDR)
{
return AsVar(addr)->def->src1;
}
tmp = CreateTemp(ty);
GenerateAssign(ty, tmp, DEREF, addr, NULL);
return tmp;
}
Symbol AddressOf(Symbol p)
{
if (p->kind == SK_Temp && AsVar(p)->def->op == DEREF)
{
return AsVar(p)->def->src1;
}
p->addressed = 1;
if (p->kind == SK_Variable)
{
TrackValueChange(p);
}
return TryAddValue(T(POINTER), ADDR, p, NULL);
}
Symbol TryAddValue(Type ty, int op, Symbol src1, Symbol src2)
{
int h = ((unsigned)src1 + (unsigned)src2 + op) & 15;
ValueDef def = FSYM->valNumTable[h];
Symbol t;
if (op != ADDR && (src1->addressed || (src2 && src2->addressed)))
goto new_temp;
while (def)
{
if (def->op == op && (def->src1 == src1 && def->src2 == src2))
break;
def = def->link;
}
if (def && def->ownBB == CurrentBB && def->dst != NULL)
return def->dst;
new_temp:
t = CreateTemp(ty);
GenerateAssign(ty, t, op, src1, src2);
def = AsVar(t)->def;
def->link = FSYM->valNumTable[h];
FSYM->valNumTable[h] = def;
return t;
}
/* 翻译一个复合语句 */
static void TranslateCompoundStatement (AstStatement stmt)
{
AstCompoundStatement compStmt = AsComp (stmt);
AstNode p;
Vector ilocals = compStmt->ilocals;
Symbol v;
int i;
/* 翻译局部变量 */
for (i = 0; i < LEN (ilocals); ++i) {
InitData initd;
Type ty;
Symbol dst, src;
int size;
v = GET_ITEM (ilocals, i);
initd = AsVar(v)->idata;
size = 0;
while (initd != NULL) {
if (initd->offset != size) {
dst = CreateOffset (T(UCHAR), v, size);
GenerateClear (dst, initd->offset - size);
}
ty = initd->expr->ty;
if (initd->expr->op == OP_STR) {
String str = initd->expr->val.p;
src = AddString (ArrayOf (str->len + 1, ty->bty), str);
} else {
src = TranslateExpression (initd->expr);
}
dst = CreateOffset (ty, v, initd->offset);
/* 赋值 */
GenerateMove (ty, dst, src);
size = initd->offset + ty->size;
initd = initd->next;
}
if (size < v->ty->size) {
dst = CreateOffset (T(UCHAR), v, size);
GenerateClear (dst, v->ty->size - size);
}
}
for (p = compStmt->stmts; p; p = p->next) {
TranslateStatement ((AstStatement)p);
}
}
/* 操作为非取地址时,目标值置空 */
static void TrackValueChange (Symbol p)
{
ValueUse use = AsVar(p)->uses;
for ( ; use; use = use->next) {
/* 操作为非取地址时,目标值置空 */
if (use->def->op != ADDR)
use->def->dst = NULL;
}
}
static void TrackValueChange(Symbol p)
{
ValueUse use = AsVar(p)->uses;
while (use)
{
if (use->def->op != ADDR)
use->def->dst = NULL;
use = use->next;
}
}
/* 创建偏移符号 */
Symbol CreateOffset (Type ty, Symbol base, int coff)
{
VariableSymbol p;
if (0 == coff)
return base;
CALLOC (p);
if (SK_Offset == base->kind) {
coff += AsVar(base)->offset;
base = base->link;
}
p->addressed = 1;
p->kind = SK_Offset;
p->ty = ty;
p->link = base;
p->offset = coff;
p->name = FormatName ("%s[%d]", base->name, coff);
base->ref++;
return (Symbol)p;
}
/* 尝试添加操作的值
* 在函数符号表中查找该操作,
* 如果找到复合条件的则返回目标符号,
* 否则创建值并添加到符号表中 */
Symbol TryAddValue (Type ty, int op, Symbol src1, Symbol src2)
{
int h = ((unsigned long long)src1 + (unsigned long long)src2 + op) & 15;
ValueDef def;
Symbol t;
/* 非地址符号 */
if (op != ADDR && (src1->addressed || (src2 && src2->addressed)))
goto new_temp;
/* 在函数的符号表中查找此操作的值 */
for (def = FSYM->valNumTable[h]; def; def = def->link) {
if (def->op == op && (def->src1 == src1 && def->src2 == src2))
break;
}
/* 如果查找到该值,并属于当前基本块,并且有目标符号,则直接返回,
* 否则创建中间变量 */
if (def && def->ownBB == CurrentBB && def->dst != NULL)
return def->dst;
/* 创建新临时变量 */
new_temp:
/* 创建临时变量添加到函数符号表中 */
t = CreateTemp (ty);
/* 构造一个三地址码,并添加到当前块中 */
GenerateAssign (ty, t, op, src1, src2);
/* t->def 是在GenerateAssign 中构造的值 */
def = AsVar(t)->def;
/* 添加值到符号表中 */
def->link = FSYM->valNumTable[h];
FSYM->valNumTable[h] = def;
return t;
}
/**
* Perform algebraic simplification and strenth reduction
*/
Symbol Simplify(Type ty, int opcode, Symbol src1, Symbol src2)
{
VariableSymbol t;
Symbol p1, p2;
int c1, c2;
if (IsRealType(ty))
goto add_value;
if (src2 == NULL || (src2->kind != SK_Constant && opcode != SUB))
goto add_value;
switch (opcode)
{
case ADD:
// a + 0 = a
if (src2->val.i[0] == 0)
return src1;
// a + c1 + c2 = a + (c1 + c2)
// a - c1 + c2 = a + (-c1 + c2)
p1 = src1; c1 = 0;
if (src1->kind == SK_Temp)
{
t = AsVar(src1);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB))
{
p1 = t->def->src1;
c1 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
}
if (c1 != 0)
{
src1 = p1;
src2 = IntConstant(c1 + src2->val.i[0]);
}
break;
case SUB:
// a - 0 = a
if (src2->kind == SK_Constant && src2->val.i[0] == 0)
return src1;
// put source operand into v + c format (v maybe NULL, c maybe 0)
p1 = src1; c1 = 0;
if (src1->kind == SK_Temp)
{
t = AsVar(src1);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB))
{
p1 = t->def->src1;
c1 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
}
else if (src1->kind == SK_Constant)
{
p1 = NULL;
c1 = src1->val.i[0];
}
p2 = src2; c2 = 0;
if (src2->kind == SK_Temp)
{
t = AsVar(src2);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB))
{
p2 = t->def->src1;
c2 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
}
else if (src2->kind == SK_Constant)
{
p2 = NULL;
c2 = src2->val.i[0];
}
if (p1 == p2)
{
// (a + c1) - (a + c2) = c1 - c2
return IntConstant(c1 - c2);
}
else if (p1 == NULL)
{
// c1 - (a + c2) = (c1 - c2) - a
src1 = IntConstant(c1 - c2);
src2 = p2;
}
else if (p2 == NULL)
{
// (a + c1) - c2 = a + (c1 - c2)
src1 = p1;
opcode = ADD;
src2 = IntConstant(c1 - c2);
}
break;
case MUL:
case DIV:
// a * 1 = a; a / 1 = a;
if (src2->val.i[0] == 1)
return src1;
// a * 2 power of n = a >> n
c1 = Power2(src2->val.i[0]);
if (c1 != 0)
{
src2 = IntConstant(c1);
opcode = opcode == MUL ? LSH : RSH;
}
break;
case MOD:
// a % 1 = 0
if (src2->val.i[0] == 1)
return IntConstant(0);
// a % 2 power of n = a & (2 power of n - 1)
c1 = Power2(src2->val.i[0]);
if (c1 != 0)
{
src2 = IntConstant(src2->val.i[0] - 1);
opcode = BAND;
}
break;
case LSH:
case RSH:
// a >> 0 = a << 0 = a
if (src2->val.i[0] == 0)
return src1;
break;
case BOR:
// a | 0 = a; a | -1 = -1
if (src2->val.i[0] == 0)
return src1;
if (src2->val.i[0] == -1)
return src2;
break;
case BXOR:
// a ^ 0 = a
if (src2->val.i[0] == 0)
return src1;
break;
case BAND:
// a & 0 = 0, a & -1 = a
if (src2->val.i[0] == 0)
return IntConstant(0);
if (src2->val.i[0] == -1)
return src1;
break;
default:
break;
}
add_value:
return TryAddValue(ty, opcode, src1, src2);
}
static void PeepHole(BBlock bb)
{
IRInst inst = bb->insth.next;
IRInst ninst;
while (inst != &bb->insth)
{
ninst = inst->next;
if ((inst->opcode == CALL || (inst->opcode >= EXTI1 && inst->opcode <= CVTF8U4)) &&
ninst->opcode == MOV && inst->opds[0] == ninst->opds[1])
{
inst->opds[0]->ref -= 2;
inst->opds[0] = ninst->opds[0];
inst->next = ninst->next;
ninst->next->prev = inst;
bb->ninst--;
if (ninst->opds[0]->kind == SK_Temp)
DefineTemp(ninst->opds[0], inst->opcode, (Symbol)inst, NULL);
}
else if ((inst->opcode == MOV || inst->opcode == IMOV) && inst->opds[1]->kind == SK_Temp)
{
ValueDef def = AsVar(inst->opds[1])->def;
IRInst p;
if (def->op == MOV)
{
while (def != NULL)
{
p = (IRInst)def->src1;
p->opds[0]->ref--;
inst->opds[0]->ref++;
p->opds[0] = inst->opds[0];
p->opcode = inst->opcode;
def = def->link;
}
inst->opds[0]->ref--;
inst->opds[1]->ref--;
inst->prev->next = inst->next;
inst->next->prev = inst->prev;
}
}
else if ((inst->opcode == ADD || inst->opcode == SUB) && ninst->opcode == MOV &&
inst->opds[0] == ninst->opds[1] && inst->opds[1] == ninst->opds[0] &&
inst->opds[2]->kind == SK_Constant)
{
int tcode = TypeCode(inst->ty);
if ((tcode == F4 && inst->opds[2]->val.f == 1.0f) ||
(tcode == F8 && inst->opds[2]->val.d == 1.0) ||
(inst->opds[2]->val.i[0] == 1))
{
inst->opds[0]->ref -= 2;
inst->opds[1]->ref--;
inst->opds[2]->ref--;
inst->opcode = inst->opcode == ADD ? INC : DEC;
inst->opds[0] = inst->opds[1];
inst->opds[1] = inst->opds[2] = NULL;
inst->next = ninst->next;
ninst->next->prev = inst;
}
}
inst = inst->next;
}
}
/* 算数优化 */
Symbol Simplify (Type ty, int opcode, Symbol src1, Symbol src2)
{
VariableSymbol t;
Symbol p1, p2;
int c1, c2;
/* 浮点 */
if (IsRealType (ty))
goto add_value;
if (src2 == NULL || (src2->kind != SK_Constant && opcode != SUB))
goto add_value;
/* 以下是 加, 减, 乘, 除, 取余, 左移, 右移, 按位操作的优化 */
switch (opcode) {
case ADD: {
/* a + 0 = a */
if (src2->val.i[0] == 0)
return src1;
/* a + c1 + c2 = a + (c1 + c2) */
/* a - c1 + c2 = a + (-c1 + c2) */
p1 = src1; c1 = 0;
if (src1->kind == SK_Temp) {
t = AsVar(src1);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB)) {
p1 = t->def->src1;
c1 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
}
if (c1 != 0) {
src1 = p1;
/* 合并c1, c2 */
src2 = IntConstant (c1 + src2->val.i[0]);
}
}break;
case SUB: {
/* a - 0 = a */
if (src2->kind == SK_Constant && src2->val.i[0] == 0)
return src1;
// put source operand into v + c format (v maybe NULL, c maybe 0)
p1 = src1; c1 = 0;
if (src1->kind == SK_Temp) {
t = AsVar(src1);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB)) {
p1 = t->def->src1;
c1 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
} else if (src1->kind == SK_Constant) {
p1 = NULL;
c1 = src1->val.i[0];
}
p2 = src2; c2 = 0;
if (src2->kind == SK_Temp) {
t = AsVar(src2);
if (t->def->src2 && t->def->src2->kind == SK_Constant &&
(t->def->op == ADD || t->def->op == SUB)) {
p2 = t->def->src1;
c2 = (t->def->op == ADD ? 1 : -1) * t->def->src2->val.i[0];
}
} else if (src2->kind == SK_Constant) {
p2 = NULL;
c2 = src2->val.i[0];
}
if (p1 == p2) {
/* (a + c1) - (a + c2) = c1 - c2 */
return IntConstant (c1 - c2);
} else if (p1 == NULL) {
/* c1 - (a + c2) = (c1 - c2) - a */
src1 = IntConstant (c1 - c2);
src2 = p2;
} else if (p2 == NULL) {
/* (a + c1) - c2 = a + (c1 - c2) */
src1 = p1;
opcode = ADD;
src2 = IntConstant(c1 - c2);
}
}break;
case MUL: case DIV: {
/* a * 1 = a; a / 1 = a; */
if (src2->val.i[0] == 1)
return src1;
/* a * 2 power of n = a >> n */
c1 = Power2 (src2->val.i[0]);
if (c1 != 0) {
/* 转换乘除为位移操作 */
src2 = IntConstant (c1);
opcode = opcode == MUL ? LSH : RSH;
}
}break;
case MOD: {
/* a % 1 = 0 */
if (src2->val.i[0] == 1)
return IntConstant (0);
/* a % 2 power of n = a & (2 power of n - 1) */
c1 = Power2 (src2->val.i[0]);
if (c1 != 0) {
src2 = IntConstant (src2->val.i[0] - 1);
opcode = BAND;
}
}break;
case LSH: case RSH: {
/* a >> 0 = a << 0 = a */
if (src2->val.i[0] == 0)
return src1;
}break;
case BOR: {
/* a | 0 = a; a | -1 = -1 */
if (src2->val.i[0] == 0)
return src1;
if (src2->val.i[0] == -1)
return src2;
}break;
case BXOR: {
/* a ^ 0 = a */
if (src2->val.i[0] == 0)
return src1;
}break;
case BAND: {
/* a & 0 = 0, a & -1 = a */
if (src2->val.i[0] == 0)
return IntConstant(0);
if (src2->val.i[0] == -1)
return src1;
}break;
default: break;
}
add_value:
/* 构造值添加到符号表中,并返回 */
return TryAddValue (ty, opcode, src1, src2);
}
/**
* Get a symbol's name in assembly
*/
static char* GetAccessName(Symbol p)
{
if (p->aname != NULL)
return p->aname;
switch (p->kind)
{
case SK_Constant:
if (p->name[0] == '0' && p->name[1] == 'x')
p->aname = FormatName("0%sH", &p->name[2]);
else
p->aname = p->name;
break;
case SK_String:
case SK_IRegister:
case SK_Label:
p->aname = p->name;
break;
case SK_Variable:
case SK_Temp:
if (p->level == 0)
{
p->aname = FormatName("_%s", p->name);
}
else if (p->sclass == TK_STATIC)
{
p->aname = FormatName("%s%d", p->name, TempNum++);
}
else
{
p->aname = FormatName("(%d)[ebp]", AsVar(p)->offset);
}
break;
case SK_Function:
p->aname = FormatName("_%s", p->name);
break;
case SK_Offset:
{
Symbol base = p->link;
int n = AsVar(p)->offset;
if (base->level == 0 || base->sclass == TK_STATIC)
{
p->aname = FormatName("%s%s%d", GetAccessName(base), n >= 0 ? "+" : "", n);
}
else
{
n += AsVar(base)->offset;
p->aname = FormatName("(%d)[ebp]", n);
}
}
break;
default:
assert(0);
}
return p->aname;
}
