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Remove dead JMP/JMPZ/JMPNZ/JMPZNZ (DCE pass can't remove them)

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This commit is contained in:
Dmitry Stogov 2017-07-18 20:43:06 +03:00
parent 582882ae18
commit 0903f6bffb
1 changed files with 83 additions and 0 deletions
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83
ext/opcache/Optimizer/dfa_pass.c
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@ -450,6 +450,84 @@ int zend_dfa_optimize_calls(zend_op_array *op_array, zend_ssa *ssa)
return removed_ops;
}
static int zend_dfa_optimize_jmps(zend_op_array *op_array, zend_ssa *ssa)
{
int removed_ops = 0;
int block_num = 0;
while (block_num < ssa->cfg.blocks_count
&& !(ssa->cfg.blocks[block_num].flags & ZEND_BB_REACHABLE)) {
block_num++;
}
while (block_num < ssa->cfg.blocks_count) {
int next_block_num = block_num + 1;
zend_basic_block *block = &ssa->cfg.blocks[block_num];
uint32_t op_num;
zend_op *opline;
zend_ssa_op *op;
while (next_block_num < ssa->cfg.blocks_count
&& !(ssa->cfg.blocks[next_block_num].flags & ZEND_BB_REACHABLE)) {
next_block_num++;
}
if (block->len) {
if (block->successors_count == 2) {
if (block->successors[0] == block->successors[1]) {
op_num = block->start + block->len - 1;
opline = op_array->opcodes + op_num;
switch (opline->opcode) {
case ZEND_JMPZ:
case ZEND_JMPNZ:
case ZEND_JMPZNZ:
op = ssa->ops + op_num;
if (block->successors[0] == next_block_num) {
if (opline->op1_type & (IS_CV|IS_CONST)) {
zend_ssa_remove_instr(ssa, opline, op);
if (op->op1_use >= 0) {
zend_ssa_unlink_use_chain(ssa, op_num, op->op1_use);
op->op1_use = -1;
op->op1_use_chain = -1;
}
MAKE_NOP(opline);
removed_ops++;
} else {
opline->opcode = ZEND_FREE;
opline->op2.num = 0;
}
} else {
if (opline->op1_type & (IS_CV|IS_CONST)) {
if (op->op1_use >= 0) {
zend_ssa_unlink_use_chain(ssa, op_num, op->op1_use);
op->op1_use = -1;
op->op1_use_chain = -1;
}
opline->opcode = ZEND_JMP;
opline->op1_type = IS_UNUSED;
opline->op1.num = opline->op2.num;
}
}
break;
default:
break;
}
}
} else if (block->successors_count == 1 && block->successors[0] == next_block_num) {
op_num = block->start + block->len - 1;
opline = op_array->opcodes + op_num;
if (opline->opcode == ZEND_JMP) {
MAKE_NOP(opline);
removed_ops++;
}
}
}
block_num = next_block_num;
}
return removed_ops;
}
void zend_dfa_optimize_op_array(zend_op_array *op_array, zend_optimizer_ctx *ctx, zend_ssa *ssa, zend_call_info **call_map)
{
if (ctx->debug_level & ZEND_DUMP_BEFORE_DFA_PASS) {
@ -467,6 +545,11 @@ void zend_dfa_optimize_op_array(zend_op_array *op_array, zend_optimizer_ctx *ctx
if (sccp_optimize_op_array(ctx, op_array, ssa, call_map)) {
remove_nops = 1;
}
if (zend_dfa_optimize_jmps(op_array, ssa)) {
remove_nops = 1;
}
#if ZEND_DEBUG_DFA
ssa_verify_integrity(op_array, ssa, "after sccp");
#endif